Faqs on asp.net - part1

2.1 What is ASP.NET?
ASP.NET is a programming framework built on the common language runtime that can be used on a server to build powerful Web applications.
For more details refer
What is ASP.NET ASP.NET OverView

2.2 Why does my ASP.NET file have multiple

tag with runat=server?
This means that ASP.Net is not properly registered with IIS. .Net framework provides an Administration utility that manages the installation and uninstallation of multiple versions of ASP.NET on a single machine. You can find the file in C:\WINNT\Microsoft.NET\Framework\v**\aspnet_regiis.exe
use the command: aspnet_regiis.exe -u ---> to uninstall current asp.net version. use the command: aspnet_regiis.exe -i ---> to install current asp.net version.

For Windows Server 2003, you must use aspnet_regiis -i -enable This is because of the "Web Service Extensions" feature in IIS 6
(if you install VS.NET or the framework without IIS installed, and then go back in and install IIS afterwards, you have to re-register so that ASP.NET 'hooks' into IIS properly."
2.3 How to find out what version of ASP.NET I am using on my machine?
VB.NET
Response.Write(System.Environment.Version.ToString() )

C#
Response.Write(System.Environment.Version.ToString() );


2.4 Is it possible to pass a querystring from an .asp page to aspx page?
Yes you can pass querystring from .asp to ASP.NET page .asp
<%response.redirect "webform1.aspx?id=11"%>

.aspxVB.NET
Response.Write (Request("id").ToString ())

C#
Response.Write (Request["id"].ToString ());


2.5 How to comment out ASP.NET Tags?


2.6 What is a ViewState?
In classic ASP, when a form is submitted the form values are cleared. In some cases the form is submitted with huge information. In such cases if the server comes back with error, one has to re-enter correct information in the form. But submitting clears up all form values. This happens as the site does not maintain any state (ViewState).
In ASP .NET, when the form is submitted the form reappears in the browser with all form values. This is because ASP .NET maintains your ViewState. ViewState is a state management technique built in ASP.NET. Its purpose is to keep the state of controls during subsequent postbacks by the same user. The ViewState indicates the status of the page when submitted to the server. The status is defined through a hidden field placed on each page with a control.


If you want to NOT maintain the ViewState, include the directive at the top of an .aspx page If you do not want to maintain Viewstate for any control add the attribute EnableViewState="false" to any control. For more details refer The ASP.NET View State
2.7 Where can I get the details on Migration of existing projects using various technologies to ASP.NET?
Microsoft has designed Migration Assistants to help us convert existing pages and applications to ASP.NET. It does not make the conversion process completely automatic, but it will speed up project by automating some of the steps required for migration. Below are the Code Migration Assistants
ASP to ASP.NET Migration Assistant PHP to ASP.NET Migration Assistant JSP to ASP.NET Migration Assistant Refer Migrating to ASP.Net
2.8 What is the equivalent of date() and time() in ASP.NET?
VB.NET
System.DateTime.Now.ToShortDateString() System.DateTime.Now.ToShortTimeString()

C#
System.DateTime.Now.ToShortDateString(); System.DateTime.Now.ToShortTimeString();


2.9 How to prevent a button from validating it's form?
Set the CauseValidation property of the button control to False
2.10 How to get the IP address of the host accessing my site?
VB.NET
Response.Write (Request.UserHostAddress.ToString ())

C#
Response.Write (Request.UserHostAddress.ToString ());


2.11 How to access the Parameters passed in via the URL?
Call the Request.QueryStringmethod passing in the key. The method will return the parameter value associated with that key. VB.NET
Request.QueryString("id")

C#
Request.QueryString["id"];


2.12 How to Set Focus to Web Form Controls By Using Client-Side Script?


Refer Sample IE Code
2.13 How to display a Wait page while a query is running?
Refer Asynchronous Wait State Pattern in ASP.NET
2.14 How to implement Form based Authentication in ASP.NET application?
For
VB.NET C#

2.15 How to catch the 404 error in my web application and provide more useful information?
In the global.asax Application_error Event write the following code
VB.NET
Dim ex As Exception = Server.GetLastError().GetBaseException() If TypeOf ex Is System.IO.FileNotFoundException Then 'your code 'Response.Redirect("err404.aspx") Else 'your code End If

C#
Exception ex = Server.GetLastError().GetBaseException(); if (ex.GetType() == typeof(System.IO.FileNotFoundException)) { //your code Response.Redirect ("err404.aspx"); } else { //your code }


2.16 Is there a method similar to Response.Redirect that will send variables to the destination page other than using a query string or the post method?
Server.Transfer preserves the current page context, so that in the target page you can extract values and such. However, it can have side effects; because Server.Transfer doesnt' go through the browser, the browser doesn't update its history and if the user clicks Back, they go to the page previous to the source page.
Another way to pass values is to use something like a LinkButton. It posts back to the source page, where you can get the values you need, put them in Session, and then use Response.Redirect to transfer to the target page. (This does bounce off the browser.) In the target page you can read the Session values as required.
Refer to Passing Values Between Web Forms Pages for more information.
2.17 What are the differences between HTML versus Server Control?
Refer
ASP.NET Server Controls Recommendations Introduction to ASP.NET Server Controls

2.18 How can I change the action of a form through code?
You can't change it. The action attribute is owned by ASP.NET. Handle Events and Transfer.
For work around refer to Paul Wilson's Multiple Forms and Non-PostBack Forms - Solution
2.19 Is there any control that allows user to select a time from a clock - in other words is there a clock control?
Peter Blum has developed some controls. Check out Peter's Date Package: TimeOfDayTextBox and DurationTextBox Controls
2.20 How to Compare time?
VB.NET
Dim t1 As String = DateTime.Parse("3:30 PM").ToString("t") Dim t2 As String = DateTime.Now.ToString("t") If DateTime.Compare(DateTime.Parse(t1), DateTime.Parse(t2)) <> than " & t2.ToString()) End If

C#
string t1 = DateTime.Parse("3:30 PM").ToString("t"); string t2 = DateTime.Now.ToString("t"); if (DateTime.Compare(DateTime.Parse (t1), DateTime.Parse (t2)) <> than " + t2.ToString()); }


2.21 How To work with TimeSpan Class?
VB.NET
Dim adate As DateTime = DateTime.Parse("06/24/2003") Dim bdate As DateTime = DateTime.Parse("06/28/2003") Dim ts As New TimeSpan(bdate.Ticks - adate.Ticks) Response.Write(ts.TotalDays & "
") Response.Write(ts.TotalHours & ":" & ts.TotalMinutes & ":" & ts.TotalSeconds & ":" & ts.TotalMilliseconds)

C#
DateTime adate = DateTime.Parse("06/24/2003"); DateTime bdate = DateTime.Parse("06/28/2003"); TimeSpan ts = new TimeSpan (bdate.Ticks - adate.Ticks); Response.Write(ts.TotalDays.ToString () + "
"); Response.Write(ts.TotalHours.ToString() + ":" + ts.TotalMinutes.ToString() + ":" + ts.TotalSeconds.ToString() + ":" + ts.TotalMilliseconds.ToString() );


2.22 Where can I get information on Cookies in ASP.NET?
Refer Mike Pope's article Basics of Cookies in ASP.NET
2.23 Does ASP.Net still recognize the global.asa file?
ASP.Net does not recognize the standard ASP global.asa file. Instead it uses a file named global.asax with the same - plus additional - functionality.
2.24 How should I destroy my objects in ASP.Net?
ASP.Net actually has very solid internal garbage collection. So this is not an issue as it was in previous versions of Active Server Pages. Link to more information: Element
2.25 Are there resources online with tips on ASP to ASP.Net conversions?
Microsoft has desiged The ASP to ASP.NET Migration Assistant help us convert ASP pages and applications to ASP.NET. It does not make the conversion process completely automatic, but it will speed up project by automating some of the steps required for migration.
The following Code Migration Assistants are discussed in the link below.
ASP to ASP.NET Migration Assistant PHP to ASP.NET Migration Assistant JSP to ASP.NET Migration Assistant Refer Migrating to ASP.Net Also refer:
Microsoft's ASP to ASP.NET Code Migration Assistant John Peterson's article Microsoft's ASP to ASP.NET Migration Assistant Paolo Cavone's article From ASP to ASP.NET... Painlessly!

2.26 How do I publish my ASP.NET application to my ISP's web server?
Your ISP must first create an IIS application and apply the Front Page Server Extensions to it. Then in Visual Studio .NET, select the "Project Copy Project" menu. Then enter the URL and select the FrontPage web access method. The "Copy Project" feature copies all of the necessary files to your ISP's machine for your ASP.NET application to run.
You can also FTP your files to your ISP web server. But you must know which files to upload. For more details refer PRB: Remote ASP.NET Projects Require IIS on the Client Computer or FrontPage Server Extensions on the Server Computer
2.27 Why do i get error message "Could not load type" whenever I browse to my ASP.NET web site?
Your code-behind files for either your .aspx or the global.aspx page have not been complied. Use Visual Studio .NET's "Build Build Solution" menu, or run the command line compiler.
For more details refer PRB: "Could not load type" error message when you browse to .aspx page
2.28 Will the WebMatrix SqlDataSourceControl work with a MySQL connection?
SqlDataSourceControl lets you connect and work with MS SQL DB, while AccessDataSourceControl do the same thing but for MS Access DB. Therefore SqlDataSourceControl can't help you in your MySql connectivity .For Connectivity with MySql refer Accessing MySQL Database with ASP.NET
2.29 Can I combine classic ASP and ASP.NET pages?
No. ASP pages can run in the same site as ASP.NET pages, but you can't mix in a page. Also ASP and ASP.NET won't share their session.
2.30 What is the difference between src and Code-Behind?
Src attribute means you deploy the source code files and everything is compiled JIT (just-in-time) as needed. Many people prefer this since they don't have to manually worry about compiling and messing with dlls -- it just works. Of course, the source is now on the server, for anyone with access to the server -- but not just anyone on the web.
CodeBehind attribute doesn't really "do" anything, its just a helper for VS.NET to associate the code file with the aspx file. This is necessary since VS.NET automates the pre-compiling that is harder by hand, and therefore the Src attribute is also gone. Now there is only a dll to deploy, no source, so it is certainly better protected, although its always decompilable even then.
2.31 How can I get the value of input box with type hidden in code-behind?
You can set the runat= server for the hidden control and you can use ControlName.Value to get its value in CodeBehind file
2.32 I have created a .NET user control page (.ascx) but I cannot compile and run it.
User control (ascx) can't be run on it own, but you can drag it onto any web page (aspx) and then run it.
2.33 What is a .resx file?
The .resx resource file format consists of XML entries, which specify objects and strings inside XML tags. This is useful for localization. For more details refer Resources in .resx files
2.34 Is it possible to use a style sheet class directly on a control instead of using inline or page-level formatting ?
Every WebControl derived control has a CssClass property which allows you to set it's format to a style sheet.
2.35 Can I recieve both HTML markup for page and code in the ASP.NET web page's source code portion in the Web browser?
No. The Web browser receives only HTML markup. No source code or web control syntax is passed back to the web browser.
2.36 Why can't I put where at the top of an ASPX file and write my server-side scripts in C ?
The parsers ASP.NET uses to extract code from ASPX files understand C#, Visual Basic.NET, and JScript.NET. You can write server-side scripts in any language supported by a .NET compiler.
2.37 ASP pages that worked pefectly on Windows 2000 Server and IIS 5.0 do not work on Windows 2003 Server with IIS 6.0. ASP.NET pages work fine. Why?
Start -> Settings -> Control Panel -> Administrative Tools -> and double clicking IIS Manager. Go to the Web Service Extensions tab, click Active Server Pages, then press the "Allow" button on the left
2.38 Why do I get error message "Error creating assembly manifest: Error reading key file 'key.snk' -- The system cannot find the file specified"?
Check the location of the key.snk file relative to the assembly file. Provide an explicit path or a relative path.


2.39 How to get URL without querystring?
VB.NET
Dim stringUri As String = "http://www.funandtech.blogspot.com/?id=1&auid=16" Dim weburi As Uri = New Uri(stringUri) Dim query As String = weburi.Query Dim weburl As String = stringUri.Substring(0, stringUri.Length - query.Length) Response.Write(weburl)

C#
string stringUri = "http://www.funandtech.blogspot.com/?id=1&auid=16"; Uri weburi = new Uri(stringUri); string query = weburi.Query; string weburl = stringUri.Substring(0, stringUri.Length - query.Length); Response.Write (weburl);


2.40 What is the best way to output only time and not Date?
Use DateTime as follows VB.NET
Response.Write(DateTime.Now.ToString("hh:mm:ss"))

C#
Response.Write(DateTime.Now.ToString("hh:mm:ss"));


2.41 Do I have to compile code if I am changing the content of my aspx.cs file?
Yes if you have used Codebehind="my.aspx.cs". Not if you used src="my.aspx.cs" in your page declaration.
2.42 How to grab the referring URL?
VB.NET
Response.Write ( Request.UrlReferrer.ToString())

C#
Response.Write ( Request.UrlReferrer.ToString());


2.43 My ASP code gives an error "Compiler Error Message: BC30289: Statement cannot appear within a method body. End of method assumed" when changed to .aspx?

2.58 How to validate that a string is a valid date?
VB.NET
Dim blnValid As Boolean = False Try DateTime.Parse(MyString) blnValid = True Catch blnValid = False End Try

C#
bool blnValid=false; try { DateTime.Parse(MyString); blnValid=true; } catch { blnValid=false; }



2.59 Are namespaces and Class names Case Sensitive?
Namespaces and Class names are case Sensitive. Namespaces imported using the @ Import Directive will cause an error if the correct case is not used.
2.60 How to convert string to a DateTime and compare it with another DateTime?
VB.NET
Dim blntimeIsOk As Boolean = DateTime.Parse("15:00") < blntimeisok =" (DateTime.Parse(">2.61 How to get the url of page dynamically?
Use Request.Url property
2.62 How to convert user input in dMy format to Mdy?
VB.NET
Dim dt As DateTime = DateTime.ParseExact("0299", New String() {"My", "M/y"}, Nothing, System.Globalization.DateTimeStyles.None)

C#
DateTime dt = DateTime.ParseExact("0299", new string[] {"My","M/y"}, null,System.Globalization.DateTimeStyles.None);

For more details refer DateTime.ParseExact
2.63 When the User is prompted a File Download dialogbox, if the user selects "Save" then the "Save as" dialog box is displayed. Is there any way for me to retrieve the filename and directory path specified by the user on the File Download dialog box?
Clients do not report information back about where the user selects to save the content, so there isn't an easy way to do this. Instead, you would need to ask the user before using the content-disposition for a file path, and then you could specify the filename parameter for the content-disposition header. Still, the user is free to change that path when actually downloading.
2.64 How to hide or show Controls in server side code?
In any appropriate event write VB.NET
TextBox1.Visible =not TextBox1.Visible

C#
TextBox1.Visible =!TextBox1.Visible ;


2.65 How to check if the user is using a secure or non secure connection?
The Request Object defines a Property called IsSecureConnection, that will indicate whether http:// or https:// has been used.
2.66 Is it possible to write code in many languages in one ASP.NET project?
You cannot write the code-behind files in different languages in the same project, but you can write the aspx pages and ascx controls in different languages.
2.67 What is the difference between Response.Redirect() and Server.Transfer().
Response.Redirect
Transfers the page control to the other page, in other words it sends the request to the other page. Causes the client to navigate to the page you are redirecting to. In http terms it sends a 302 response to the client, and the client goes where it's told. Server.Transfer Only transfers the execution to another page and during this you will see the URL of the old page since only execution is transfered to new page and not control. Occurs entirely on the server, no action is needed by the client Sometimes for performance reasons, the server method is more desirable
2.68 How to get the hostname or IP address of the server?
You can use either of these:
HttpContext.Current.Server.MachineName HttpContext.Current.Request.ServerVariables["LOCAL_ADDR"] The first one should return the name of the machine, the second returns the local ip address. Note that name of the machine could be different than host, since your site could be using host headers
2.69 What is the meaning of validateRequest=true in .net framework1.1?
The value of validateRequest is set to 'true' by default, which means that the framework will automatically deny submission of the '<' and '>' characters.
2.70 What is the different between <%# %>and <%= %>?
The <%# %>is used for databinding where as <%= %>is used to output the result of an expression. The expression inside <%# %>will be executed only when you call the page's or control's DataBind method. The expression inside <%= %>will be executed and displayed as and when it appears in the page.
2.71 What permissions do ASP.NET applications posses by default?
By default ASP.NET Web applications run as ASP.NET user. This user has limited permissions equivalent to the User Group.
2.72 How can I specify the relative path for a file?
Suppose you have following file hierarchy:
default.aspx Admin/login.aspx Misc/testpage.aspx

And you are on the login.aspx and want your user to navigate to the default.aspx (or testpage.aspx) file. Then you can use
Response.Redirect ("../default.aspx") Response.Redirect ("../Misc/testpage.aspx")

2.73 How can I specify the "upload a file" input textbox in a form to be read only so that the user can click on the browse button and pick a file but they cannot type anything into the textbox next to the browse button.

2.74 How to change the Page Title dynamically?

VB.NET
'Declare Protected WithEvents Title1 As System.Web.UI.HtmlControls.HtmlGenericControl
'In Page_Load Title1.InnerText ="Page 1"

C#
//Declare protected System.Web.UI.HtmlControls.HtmlGenericControl Title1 ;
//In Page_Load Title1.InnerText ="Page 1" ;

2.75 Why do I get the error message "Object must implement IConvertible". How can I resolve it?
The common cause for this error is specifying a control as a SqlParameter's Value instead of the control's text value. For example, if you write code as below you'll get the above error:
VB.NET
Dim nameParameter As SqlParameter = command.Parameters.Add("@name", SqlDbType.NVarChar, 50) nameParameter.Value = txtName

C#
SqlParameter nameParameter = command.Parameters.Add("@name", SqlDbType.NVarChar, 50); nameParameter.Value = txtName ;

To resolve it, specify the control's Text property instead of the control itself.
VB.NET
nameParameter.Value = txtName.Text

C#
nameParameter.Value =txtName.Text;


2.76 Why is default.aspx page not opened if i specify http://localhost. I am able to view this page if i hardcode it as http://localhost/default.aspx?
If some other default page comes higher in the list, adjust the default.aspx to be the number one entry inside the IIS configuration. If you have multiple websites inside IIS, make sure the configuration is applied on the right website (or on all websites by applying the configuration on the server-level using the properties dialog, configure WWW service).
2.77 Can ASP.NET work on an NT server?
No. For more details refer ASP 1.1 version
2.78 Is it possible to migrate Visual InterDev Design-Time Controls to ASP.NET?
Refer INFO: Migrating Visual InterDev Design-Time Controls to ASP.NET
2.79 How to automatically get the latest version of all the asp.net solution items from Source Safe when opening the solution?
In VS.NET you can go to Tools > Options > Source Control > General and check the checkbox for Get everything when a solution opens. This retrieves the latest version of all solution items when you open the solution.
2.80 How to convert the datetime into a string for use in the SQL ' statement?

VB.NET
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load 'Put user code to initialize the page here If Not Page.IsPostBack Then Dim cInfo As CultureInfo For Each cInfo In CultureInfo.GetCultures(CultureTypes.SpecificCultures) ddlCulture.Items.Add(cInfo.Name) Next End If End Sub
Private Sub ddlCulture_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ddlCulture.SelectedIndexChanged ' Get a CultureInfo object based on culture selection in dropdownlist Dim cInfo As CultureInfo = New CultureInfo(ddlCulture.SelectedItem.Text) ' Get a CultureInfo object based on Invariant culture Dim cInfoNeutral As CultureInfo = New CultureInfo("") ' Display the datetime based on the formatting of the selected culture TextBox1.Text = Convert.ToString(Now, cInfo.DateTimeFormat) ' Create a DateTime variable to hold the Invariant time Dim dt As DateTime dt = Convert.ToDateTime(TextBox1.Text, cInfo.DateTimeFormat) 'Convert the datetime into a string for use in the SQL statement Label1.Text = "... WHERE ([Date] < '" & _ Convert.ToString(dt, cInfoNeutral.DateTimeFormat) & "')" End Sub C# private void Page_Load(object sender, System.EventArgs e) { // Put user code to initialize the page here if (!Page.IsPostBack ) { foreach(CultureInfo cInfo in CultureInfo.GetCultures(CultureTypes.SpecificCultures)) { ddlCulture.Items.Add(cInfo.Name); } } } private void ddlCulture_SelectedIndexChanged(object sender, System.EventArgs e) { // Get a CultureInfo object based on culture selection in dropdownlist CultureInfo cInfo = new CultureInfo(ddlCulture.SelectedItem.Text); // Get a CultureInfo object based on Invariant culture CultureInfo cInfoNeutral = new CultureInfo(""); // Display the datetime based on the formatting of the selected culture TextBox1.Text = Convert.ToString(DateTime.Now , cInfo.DateTimeFormat); // Create a DateTime variable to hold the Invariant time DateTime dt ; dt = Convert.ToDateTime(TextBox1.Text, cInfo.DateTimeFormat); //Convert the datetime into a string for use in the SQL statement Label1.Text = "... WHERE ([Date] < '" + Convert.ToString(dt, cInfoNeutral.DateTimeFormat) + "')"; } 2.81 How to make VS.Net use FlowLayout as the default layout rather than the GridLayout?
For VB.NET, go to path C:\Program Files\Microsoft Visual Studio .NET\Vb7\VBWizards\WebForm\Templates\1033 Change the following line in the existing WebForm1.aspx


to



For C#, go to path C:\Program Files\Microsoft Visual Studio .NET 2003\VC#\VC#Wizards\CSharpWebAppWiz\Templates\1033 Change the following line in the existing WebForm1.aspx

to
Note:Before changing any templates it's a good idea to make backup copies of them Or rather than above approach you can change the behavior for new files on a per project basis in Visual Studio by:
Right clicking on the project name (Ex: "WebApplication1)" in Solution Explorer, and select "Properties". From project properties window, under Common Properties>Designer Defaults>Page Layout change "Grid" to "Flow".

2.82 Can I use a DataReader to update/insert/delete a record?
No. DataReader provides a means of reading a forward-only stream of rows from a database.
2.83 What is the difference between Server.Transfer and Server.Execute?
Server.Transfer is used to End the current webform and begin executing a new webform. This method works only when navigating to a Web Forms page (.aspx) Server.Execute is used to begin executing a new webform while still displaying the current web form. The contents of both forms are combined. This method works only when navigating to a webform page(.aspx)

2.84 How to create a login screen in ASP.NET?
Here is a sample login screen:


VB.NET
Dim myconnection As SqlConnection Dim mycmd As SqlCommand Dim strSql As String Dim myReader As SqlDataReader
Private Sub btnLogin_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLogin.Click myconnection = New SqlConnection("Server=localhost;uid=sa;password=;database=northwind;") strSql = "Select * from usertbl where username=" & "'" & txtUserName.Text & "'" & " and userpassword=" & "'" & txtPassword.Text & "'" mycmd = New SqlCommand(strSql, myconnection) myconnection.Open() myReader = mycmd.ExecuteReader(CommandBehavior.CloseConnection) If myReader.Read() Then Response.Write("Welcome") Else Response.Write("Access Denied") End If
End Sub

C#
SqlConnection myconnection ; SqlCommand mycmd ; string strSql ; SqlDataReader myReader ; private void btnLogin_Click(object sender, System.EventArgs e) { myconnection = new SqlConnection("Server=localhost;uid=sa;password=;database=northwind;"); strSql = "Select * from usertbl where username=" + "'" + txtUserName.Text + "'" + " and userpassword=" + "'" + txtPassword.Text + "'"; mycmd = new SqlCommand(strSql, myconnection); myconnection.Open(); myReader = mycmd.ExecuteReader(CommandBehavior.CloseConnection); if (myReader.Read() ) { Response.Write("Welcome"); } else { Response.Write("Access Denied"); } }


2.85 How to format a Telephone number in the xxx-xxx-xxxx format?
VB.NET
Dim Telno As Double = Double.Parse(ds.Tables(0).Rows(0)("TelNo").ToString()) Response.Write(Telno.ToString("###-###-####"))

C#
double Telno= double.Parse(ds.Tables[0].Rows[0]["TelNo"].ToString()); Response.Write(Telno.ToString("###-###-####"));



2.86 Can two different programming languages be mixed in a single ASPX file?
No. ASP.NET uses parsers to strip the code from ASPX files and copy it to temporary files containing derived Page classes, and a given parser understands only one language
2.87 Can I use custom .NET data types in a Web form?
Yes. Place the DLL containing the type in the application root's bin directory and ASP.NET will automatically load the DLL when the type is referenced. This is also what happens when you add a custom control from the toolbox to your web form.
2.88 How can I have a particular Web page in an ASP.NET application which displays its own error page.
This can be done by setting the ErroPage attribute of Page Directive or ErrorPage property of Page Class to the desired Custom Error Page
<%@Page Language="C#" ErrorPage="specificerropage.htm"%>

In web.config
No. The Web browser receives only HTML markup. No source code or web control syntax is passed back to the web browser.
2.36 Why can't I put where at the top of an ASPX file and write my server-side scripts in C ?
The parsers ASP.NET uses to extract code from ASPX files understand C#, Visual Basic.NET, and JScript.NET. You can write server-side scripts in any language supported by a .NET compiler.
2.37 ASP pages that worked pefectly on Windows 2000 Server and IIS 5.0 do not work on Windows 2003 Server with IIS 6.0. ASP.NET pages work fine. Why?
Start -> Settings -> Control Panel -> Administrative Tools -> and double clicking IIS Manager. Go to the Web Service Extensions tab, click Active Server Pages, then press the "Allow" button on the left
2.38 Why do I get error message "Error creating assembly manifest: Error reading key file 'key.snk' -- The system cannot find the file specified"?
Check the location of the key.snk file relative to the assembly file. Provide an explicit path or a relative path.




2.39 How to get URL without querystring?
VB.NET
Dim stringUri As String = "

http://www.syncfusion.com/?id=1&auid=16" Dim weburi As Uri = New Uri(stringUri) Dim query As String = weburi.Query Dim weburl As String = stringUri.Substring(0, stringUri.Length - query.Length) Response.Write(weburl)

C#
string stringUri = "http://www.syncfusion.com/?id=1&auid=16"; Uri weburi = new Uri(stringUri); string query = weburi.Query; string weburl = stringUri.Substring(0, stringUri.Length - query.Length); Response.Write (weburl);


2.40 What is the best way to output only time and not Date?
Use DateTime as follows VB.NET
Response.Write(DateTime.Now.ToString("hh:mm:ss"))

C#
Response.Write(DateTime.Now.ToString("hh:mm:ss"));


2.41 Do I have to compile code if I am changing the content of my aspx.cs file?
Yes if you have used Codebehind="my.aspx.cs". Not if you used src="my.aspx.cs" in your page declaration.
2.42 How to grab the referring URL?
VB.NET
Response.Write ( Request.UrlReferrer.ToString())

C#
Response.Write ( Request.UrlReferrer.ToString());


2.43 My ASP code gives an error "Compiler Error Message: BC30289: Statement cannot appear within a method body. End of method assumed" when changed to .aspx?

2.58 How to validate that a string is a valid date?
VB.NET
Dim blnValid As Boolean = False Try DateTime.Parse(MyString) blnValid = True Catch blnValid = False End Try

C#
bool blnValid=false; try { DateTime.Parse(MyString); blnValid=true; } catch { blnValid=false; }



2.59 Are namespaces and Class names Case Sensitive?
Namespaces and Class names are case Sensitive. Namespaces imported using the @ Import Directive will cause an error if the correct case is not used.
2.60 How to convert string to a DateTime and compare it with another DateTime?
VB.NET
Dim blntimeIsOk As Boolean = DateTime.Parse("15:00") < blntimeisok =" (DateTime.Parse(">2.61 How to get the url of page dynamically?
Use Request.Url property
2.62 How to convert user input in dMy format to Mdy?
VB.NET
Dim dt As DateTime = DateTime.ParseExact("0299", New String() {"My", "M/y"}, Nothing, System.Globalization.DateTimeStyles.None)

C#
DateTime dt = DateTime.ParseExact("0299", new string[] {"My","M/y"}, null,System.Globalization.DateTimeStyles.None);

For more details refer DateTime.ParseExact
2.63 When the User is prompted a File Download dialogbox, if the user selects "Save" then the "Save as" dialog box is displayed. Is there any way for me to retrieve the filename and directory path specified by the user on the File Download dialog box?
Clients do not report information back about where the user selects to save the content, so there isn't an easy way to do this. Instead, you would need to ask the user before using the content-disposition for a file path, and then you could specify the filename parameter for the content-disposition header. Still, the user is free to change that path when actually downloading.
2.64 How to hide or show Controls in server side code?
In any appropriate event write VB.NET
TextBox1.Visible =not TextBox1.Visible

C#
TextBox1.Visible =!TextBox1.Visible ;


2.65 How to check if the user is using a secure or non secure connection?
The Request Object defines a Property called IsSecureConnection, that will indicate whether http:// or https:// has been used.
2.66 Is it possible to write code in many languages in one ASP.NET project?
You cannot write the code-behind files in different languages in the same project, but you can write the aspx pages and ascx controls in different languages.
2.67 What is the difference between Response.Redirect() and Server.Transfer().
Response.Redirect
Transfers the page control to the other page, in other words it sends the request to the other page. Causes the client to navigate to the page you are redirecting to. In http terms it sends a 302 response to the client, and the client goes where it's told. Server.Transfer Only transfers the execution to another page and during this you will see the URL of the old page since only execution is transfered to new page and not control. Occurs entirely on the server, no action is needed by the client Sometimes for performance reasons, the server method is more desirable
2.68 How to get the hostname or IP address of the server?
You can use either of these:
HttpContext.Current.Server.MachineName HttpContext.Current.Request.ServerVariables["LOCAL_ADDR"] The first one should return the name of the machine, the second returns the local ip address. Note that name of the machine could be different than host, since your site could be using host headers
2.69 What is the meaning of validateRequest=true in .net framework1.1?
The value of validateRequest is set to 'true' by default, which means that the framework will automatically deny submission of the '<' and '>' characters.
2.70 What is the different between <%# %>and <%= %>?
The <%# %>is used for databinding where as <%= %>is used to output the result of an expression. The expression inside <%# %>will be executed only when you call the page's or control's DataBind method. The expression inside <%= %>will be executed and displayed as and when it appears in the page.
2.71 What permissions do ASP.NET applications posses by default?
By default ASP.NET Web applications run as ASP.NET user. This user has limited permissions equivalent to the User Group.
2.72 How can I specify the relative path for a file?
Suppose you have following file hierarchy:
default.aspx Admin/login.aspx Misc/testpage.aspx

And you are on the login.aspx and want your user to navigate to the default.aspx (or testpage.aspx) file. Then you can use
Response.Redirect ("../default.aspx") Response.Redirect ("../Misc/testpage.aspx")

2.73 How can I specify the "upload a file" input textbox in a form to be read only so that the user can click on the browse button and pick a file but they cannot type anything into the textbox next to the browse button.

2.74 How to change the Page Title dynamically?

VB.NET
'Declare Protected WithEvents Title1 As System.Web.UI.HtmlControls.HtmlGenericControl
'In Page_Load Title1.InnerText ="Page 1"

C#
//Declare protected System.Web.UI.HtmlControls.HtmlGenericControl Title1 ;
//In Page_Load Title1.InnerText ="Page 1" ;


2.75 Why do I get the error message "Object must implement IConvertible". How can I resolve it?
The common cause for this error is specifying a control as a SqlParameter's Value instead of the control's text value. For example, if you write code as below you'll get the above error:
VB.NET
Dim nameParameter As SqlParameter = command.Parameters.Add("@name", SqlDbType.NVarChar, 50) nameParameter.Value = txtName

C#
SqlParameter nameParameter = command.Parameters.Add("@name", SqlDbType.NVarChar, 50); nameParameter.Value = txtName ;

To resolve it, specify the control's Text property instead of the control itself.
VB.NET
nameParameter.Value = txtName.Text

C#
nameParameter.Value =txtName.Text;


2.76 Why is default.aspx page not opened if i specify http://localhost. I am able to view this page if i hardcode it as http://localhost/default.aspx

?
If some other default page comes higher in the list, adjust the default.aspx to be the number one entry inside the IIS configuration. If you have multiple websites inside IIS, make sure the configuration is applied on the right website (or on all websites by applying the configuration on the server-level using the properties dialog, configure WWW service).
2.77 Can ASP.NET work on an NT server?
No. For more details refer ASP 1.1 version
2.78 Is it possible to migrate Visual InterDev Design-Time Controls to ASP.NET?
Refer INFO: Migrating Visual InterDev Design-Time Controls to ASP.NET
2.79 How to automatically get the latest version of all the asp.net solution items from Source Safe when opening the solution?
In VS.NET you can go to Tools > Options > Source Control > General and check the checkbox for Get everything when a solution opens. This retrieves the latest version of all solution items when you open the solution.
2.80 How to convert the datetime into a string for use in the SQL ' statement?


VB.NET
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load 'Put user code to initialize the page here If Not Page.IsPostBack Then Dim cInfo As CultureInfo For Each cInfo In CultureInfo.GetCultures(CultureTypes.SpecificCultures) ddlCulture.Items.Add(cInfo.Name) Next End If End Sub
Private Sub ddlCulture_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ddlCulture.SelectedIndexChanged ' Get a CultureInfo object based on culture selection in dropdownlist Dim cInfo As CultureInfo = New CultureInfo(ddlCulture.SelectedItem.Text) ' Get a CultureInfo object based on Invariant culture Dim cInfoNeutral As CultureInfo = New CultureInfo("") ' Display the datetime based on the formatting of the selected culture TextBox1.Text = Convert.ToString(Now, cInfo.DateTimeFormat) ' Create a DateTime variable to hold the Invariant time Dim dt As DateTime dt = Convert.ToDateTime(TextBox1.Text, cInfo.DateTimeFormat) 'Convert the datetime into a string for use in the SQL statement Label1.Text = "... WHERE ([Date] < '" & _ Convert.ToString(dt, cInfoNeutral.DateTimeFormat) & "')" End Sub C# private void Page_Load(object sender, System.EventArgs e) { // Put user code to initialize the page here if (!Page.IsPostBack ) { foreach(CultureInfo cInfo in CultureInfo.GetCultures(CultureTypes.SpecificCultures)) { ddlCulture.Items.Add(cInfo.Name); } } } private void ddlCulture_SelectedIndexChanged(object sender, System.EventArgs e) { // Get a CultureInfo object based on culture selection in dropdownlist CultureInfo cInfo = new CultureInfo(ddlCulture.SelectedItem.Text); // Get a CultureInfo object based on Invariant culture CultureInfo cInfoNeutral = new CultureInfo(""); // Display the datetime based on the formatting of the selected culture TextBox1.Text = Convert.ToString(DateTime.Now , cInfo.DateTimeFormat); // Create a DateTime variable to hold the Invariant time DateTime dt ; dt = Convert.ToDateTime(TextBox1.Text, cInfo.DateTimeFormat); //Convert the datetime into a string for use in the SQL statement Label1.Text = "... WHERE ([Date] < '" + Convert.ToString(dt, cInfoNeutral.DateTimeFormat) + "')"; } 2.81 How to make VS.Net use FlowLayout as the default layout rather than the GridLayout?
For VB.NET, go to path C:\Program Files\Microsoft Visual Studio .NET\Vb7\VBWizards\WebForm\Templates\1033 Change the following line in the existing WebForm1.aspx


to



For C#, go to path C:\Program Files\Microsoft Visual Studio .NET 2003\VC#\VC#Wizards\CSharpWebAppWiz\Templates\1033 Change the following line in the existing WebForm1.aspx


to



Note:Before changing any templates it's a good idea to make backup copies of them Or rather than above approach you can change the behavior for new files on a per project basis in Visual Studio by:
Right clicking on the project name (Ex: "WebApplication1)" in Solution Explorer, and select "Properties". From project properties window, under Common Properties>Designer Defaults>Page Layout change "Grid" to "Flow".

2.82 Can I use a DataReader to update/insert/delete a record?
No. DataReader provides a means of reading a forward-only stream of rows from a database.
2.83 What is the difference between Server.Transfer and Server.Execute?
Server.Transfer is used to End the current webform and begin executing a new webform. This method works only when navigating to a Web Forms page (.aspx) Server.Execute is used to begin executing a new webform while still displaying the current web form. The contents of both forms are combined. This method works only when navigating to a webform page(.aspx)

2.84 How to create a login screen in ASP.NET?
Here is a sample login screen:



VB.NET
Dim myconnection As SqlConnection Dim mycmd As SqlCommand Dim strSql As String Dim myReader As SqlDataReader
Private Sub btnLogin_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLogin.Click myconnection = New SqlConnection("Server=localhost;uid=sa;password=;database=northwind;") strSql = "Select * from usertbl where username=" & "'" & txtUserName.Text & "'" & " and userpassword=" & "'" & txtPassword.Text & "'" mycmd = New SqlCommand(strSql, myconnection) myconnection.Open() myReader = mycmd.ExecuteReader(CommandBehavior.CloseConnection) If myReader.Read() Then Response.Write("Welcome") Else Response.Write("Access Denied") End If
End Sub

C#
SqlConnection myconnection ; SqlCommand mycmd ; string strSql ; SqlDataReader myReader ; private void btnLogin_Click(object sender, System.EventArgs e) { myconnection = new SqlConnection("Server=localhost;uid=sa;password=;database=northwind;"); strSql = "Select * from usertbl where username=" + "'" + txtUserName.Text + "'" + " and userpassword=" + "'" + txtPassword.Text + "'"; mycmd = new SqlCommand(strSql, myconnection); myconnection.Open(); myReader = mycmd.ExecuteReader(CommandBehavior.CloseConnection); if (myReader.Read() ) { Response.Write("Welcome"); } else { Response.Write("Access Denied"); } }


2.85 How to format a Telephone number in the xxx-xxx-xxxx format?
VB.NET
Dim Telno As Double = Double.Parse(ds.Tables(0).Rows(0)("TelNo").ToString()) Response.Write(Telno.ToString("###-###-####"))

C#
double Telno= double.Parse(ds.Tables[0].Rows[0]["TelNo"].ToString()); Response.Write(Telno.ToString("###-###-####"));



2.86 Can two different programming languages be mixed in a single ASPX file?
No. ASP.NET uses parsers to strip the code from ASPX files and copy it to temporary files containing derived Page classes, and a given parser understands only one language
2.87 Can I use custom .NET data types in a Web form?
Yes. Place the DLL containing the type in the application root's bin directory and ASP.NET will automatically load the DLL when the type is referenced. This is also what happens when you add a custom control from the toolbox to your web form.
2.88 How can I have a particular Web page in an ASP.NET application which displays its own error page.
This can be done by setting the ErroPage attribute of Page Directive or ErrorPage property of Page Class to the desired Custom Error Page
<%@Page Language="C#" ErrorPage="specificerropage.htm"%>

In web.config