: ASP.NET FAQ

ASP.NET FAQ

• How do I start the process of converting my ASP web pages/site to ASP.NET?
• Why do I not see detailed error messages when I have an error in my ASP.NET page?
• Why do I receive a configuration error when I attempt to browse my ASP.NET page?
• Which ASP.NET configuration options are supported?
• How do I configure custom error messages for my .NET™ web applications?
• What file types are supported in ASP.NET?
• What is the aspnet_client directory and what is it used for?
• Are CodeBehind pages supported?
• Where do I upload my .NET assemblies?
• How do I compile my .NET web application?
• How is the global.asax file different from an ASP global.asa file?
• How should I configure Session State in my web application?
• How do I send an email message from my ASP.NET page?
• How do I upload a file from my ASP.NET page?

Q: How do I start the process of converting my ASP web pages/site to ASP.NET?

A: Microsoft® provides documentation that contains information on how to convert from ASP to ASP.NET. We recommend that you visit the following Microsoft pages for advice on how to perform ASP-to-ASP.NET conversions:

Migrating ASP Pages to ASP.NET

Migrating ASP Pages to Web Forms Pages

In addition, we suggest that you occasionally visit the Microsoft Developer's Network home page and perform a search for asp.net. Such searches will keep you up to date with the latest developments regarding ASP.NET.

Q: Why do I not see detailed error messages when I have an error in my ASP.NET page?  I only see information about a generic runtime error like the following:  

Server Error in '/appname' Application.

Runtime Error

Description: An application error occurred on the server. The current custom error settings for this application prevent the details of the application error from being viewed.

Details: To enable the details of this specific error message to be viewable on the local server machine, please create a <customerrors> tag within a "web.config" configuration file located in the root directory of the current web application. This <customerrors> tag should then have its "mode" attribute set to "RemoteOnly". To enable the details to be viewable on remote machines, please set "mode" to "Off".

Notes: The current error page you are seeing can be replaced by a custom error page by modifying the "defaultRedirect" attribute of the application's <customerrors> configuration tag to point to a custom error page URL.

A: By default, ASP.NET applications are configured with custom error messages turned off. However, some web development tools, such as Visual Studio.NET, will create a web.config file with the customErrors mode set to “RemoteOnly”. In order to enable detailed error messages, you need to make sure that you either remove the customErrors section in your web.config file or that you set the mode attribute in the customErrors section to “Off” in your site’s web.config file.  

<customerrors mode="off"/>

Be aware that when you set the customErrors mode to “Off” all visitors of your web site will see the detailed error message.

Note that due to the nature of the shared hosting platform the “RemoteOnly” and “On” modes of the customErrors section are equivalent since every visitor to your web site is browsing remotely.  

Q: Why do I receive an error like the following when I attempt to browse my ASP.NET page?

Server Error in '/appname' Application.

Configuration Error

Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.

Parser Error Message: It is an error to use a section registered as allowDefinition='MachineOnly' beyond machine.config.

A: You may have defined a section in your application’s web.config file that is not configurable on our shared web hosting platform. Remove or comment out any configuration sections from your web.config file that are not supported. See Supported Configuration Options for more information.

Q: Which ASP.NET configuration options are supported in the ASP.NET implementation on the shared web hosting platform?  

A: Many of the ASP.NET configuration options are not configurable at the site, application or subdirectory level on the shared hosting platform. Certain options can affect the security, performance and stability of the server and, therefore cannot be changed. The following settings are the only ones that can be changed in your site’s web.config file(s):  

• browserCaps
• sessionState
• clientTarget
• pages
• customErrors
• globalization
• authorization
• authentication
• webControls
• webServices
• appSettings

See Microsoft's ASP.NET Configuration for information on ASP.NET  

Q: How do I configure custom error messages for my .NET web applications?  

A: Custom Error pages can be configured in your web application's web.config file in the <customerrors> section. Below is an example of a custom error configuration:
 

With the above configuration, any 404 (File Not Found) error will be result in a redirect to the 404.aspx page. Any other error will cause the user to be redirected to the error.aspx page. On our servers, using "On" and "RemoteOnly" for the customErrors mode attribute will result in the same behavior since you will always be viewing the site remotely. Setting the mode to "Off" will cause error messages to be displayed directly to the user.

Please note that the customErrors functionality will only work for ASP.NET pages. For example, an unexpected error or a file not found error for a classic ASP file will display the standard IIS error pages.  

Q:  What file types are supported in ASP.NET?  

A: ASP.NET introduces several new file types:

• Extension: .asax
  • The Global.asax file, also known as the ASP.NET application file, is an optional file that contains code for responding to application-level events raised by ASP.NET. The System.Web.HttpForbiddenHandler is used to prevent direct requests to this file. This is the ASP.NET equivalent of the global.asa file.
    
     
• Extension: .ascx
  • Used for custom User Controls. When a page is executed with an ASCX reference, ASP.NET uses this extension to process the request. The System.Web.HttpForbiddenHandler is used to prevent direct requests to this file.
    
     
• Extension: .ashx
  • Custom HttpHandler implemented as a file rather than a separate class. HttpHandlers and HttpModules are not currently supported on our platform.
    
     
• Extension: .asmx
  • Files with these extensions contain the WebService processing directive and serves as the addressable entry point for XML Web services.
    
     
• Extension: .aspx
  • Handles requests for ASP.NET requests.
    
     
• Extension: .axd
  • Used to handle Trace requests (for debugging purposes). Tracing is not supported on our platform.
    
     
• Extension: .vsdisco
  • XML Web Service dynamic discovery document.
    
     
• Extension: .rem
  • Requests for file names with this extension are passed to the .NET remoting subsystem.
    
     
• Extension: .soap
  • Requests for file names with this extension are passed to the .NET remoting subsystem.
    
     
• Extension: .config
  • The web.config file can be used to configure many aspects of your web application. The System.Web.HttpForbiddenHandler is used to prevent direct requests to this file.
    
     
• Extension: .cs
  • C# source file. The System.Web.HttpForbiddenHandler is used to prevent direct requests to this file.
    
     
• Extension: .csproj
  • Visual C# (part of Visual Studio .NET) project file. The System.Web.HttpForbiddenHandler is used to prevent direct requests to this file.
    
     
• Extension: .vb
  • VB.NET source file. The System.Web.HttpForbiddenHandler is used to prevent direct requests to this file.
    
     
• Extension: .vbproj
  • VB.NET (part of Visual Studio .NET) project file. The System.Web.HttpForbiddenHandler is used to prevent direct requests to this file.
    
     
• Extension: .webinfo
  • Usually contains the path to the Visual Studio .NET project on the server. The System.Web.HttpForbiddenHandler is used to prevent direct requests to this file.
    
     
• Extension: .licx
  • Text based files that are used for licensing purposes. The System.Web.HttpForbiddenHandler is used to prevent direct requests to this file.
    
     
• Extension: .resx
  • XML based resource files. The System.Web.HttpForbiddenHandler is used to prevent direct requests to this file.
    
     
• Extension: .resources
  • Similar to .resx files but these types of resource file are created with the ResourceWriter class in the .NET Framework. The System.Web.HttpForbiddenHandler is used to prevent direct requests to this file.
     

Q: What is the aspnet_client directory and what is it used for?  

A: The aspnet_client directory contains JavaScript files that are used by the ASP.NET runtime for client-side validation functionality using the ASP.NET server validation controls. This directory is created automatically when ASP.NET is enabled on your site. This directory is not absolutely required for ASP.NET applications to run. It is only required if you are using client-side validation with ASP.NET server validation controls. However, we recommend you leave this directory intact.  

If you are using ASP.NET validation controls with client-side validation enabled and your aspnet_client directory is missing, your users may encounter errors. 

Q: Are CodeBehind pages supported?

A: Yes, CodeBehind pages are supported in our shared web hosting platform. For more information on CodeBehind and the ASP.NET Web Form architecture, please see Microsoft's Web Forms Code Model.  

Q:  Where do I upload my .NET assemblies?

A: Each ASP.NET application is automatically configured to look in the \bin subdirectory, located immediately under your application root, for the required .NET assemblies. By default, the root of your site is an application. Remember, you can create more than one application on your site using certain tools such as Visual Interdev or Visual Studio.NET. Each application would need its own \bin directory. If you are using Visual Studio.NET, your application (and its \bin directory) will be created automatically when you create a new web project in a subdirectory of your site.  

Q: How do I compile my .NET web application?  

A: If all of your server-side code is located within <script runat=server> tags in your .aspx files, all you need to do is upload the files to the server and they will be compiled automatically the first time they are execute. If you are using CodeBehind pages, you will have to compile your source code files into a .NET assembly and upload it to the appropriate \bin directory on the server. Using Visual Studio .NET is the simplest way to accomplish this.  

With Visual Studio.NET you can develop your web application on your local machine and then use the Copy Project feature (accessible from the VS.NET Project menu or from the Solution Explorer) to deploy your application to your web site over the FrontPage Server extensions. Please see your Visual Studio documentation for more information on how to use this feature. Another option is to create a VS.NET web project directly on the server and compile it. VS.NET will compile your project locally and upload it to the server all in one step. Again, see your Visual Studio documentation for more information.

If you do not have Visual Studio.NET, you can use the command-line compilers included with the .NET Framework SDK (download from http://www.microsoft.com/net) to compile your assemblies. You would compile them locally and then upload them to the appropriate \bin directory on the server.  

There are also other tools available that can help you compile your .NET assemblies or with your .NET development.

Q: How is the global.asax file different from an ASP global.asa file?  

A: The global.asax file is very similar to the global.asa file in classic asp. You can add a global.asax file to the root of each web application on your site. The global.asax supports the familiar Application_Start, Application_End, Session_Start, and Session_End events. In addition, ASP.NET adds support for several new events. Please see Microsoft's .NET documentation for more information.  

Q: How should I configure Session State in my web application?  

A: You can configure session state by modifying the <sessionstate> element in your web.config file. There are several options you can set in this section. 

• mode (required)
  • Off - use Off if you do not use session state in your web application. This can improve the performance of your web application.
  • InProc - this tells ASP.NET to store session state within the ASP.NET worker process(es). Please do NOT use this setting if you want reliable session state. This setting is incompatible with our configuration in the shared hosting environment. Unfortunately, if you use Visual Studio .NET to create your web.config, InProc is the default value and must be changed.
  • StateServer - this tells ASP.NET to store session state in an external process. This is the preferred mode for session state in the shared hosting environment and is our system default. 
  • SQLServer - we do not support SQLServer for storing session state in the shared hosting environment.
    
     
• cookieless (optional)
  • true or false (default) - specifies whether sessions without cookies should be used. Cookieless sessions can be especially useful if you need to support certain devices, such as cell phones, that do not support cookies.
    
     
• timeout (optional)
  • specify the time in minutes a session can be idle before it is abandoned. The default is 20. We do not recommend increasing this value.
    
     
• stateConnectionString (optional)
  • used to specify the server name and port for the session State Server. If you are going to specify this value, you should use "tcpip=127.0.0.1:42424". This is the default and you are not required to specify this value.
    
     
• sqlConnectionString (optional)
  • as mentioned above, SQLServer session state mode is not supported so you should never need to specify this attribute.
     

If you do not specify a <sessionState> section in your web.config, your application will use the defaults defined on the server. Below you can see the default configuration on the shared hosting servers:

<sessionState mode="StateServer" stateConnectionString="tcpip=127.0.0.1:42424" cookieless="false" timeout="20" />
 

Q: How do I send an email message from my ASP.NET page?

 A: You can use the System.Web.Mail.MailMessage and the System.Web.Mail.SmtpMail class to send email in your ASPX pages. Below is a simple example of using this class to send mail in C# and VB.NET. In order to send mail through our mail server, you would want to make sure to set the static SmtpServer property of the SmtpMail class to mail-fwd.  

C#

<%@ Import Namespace="System" %>
<%@ Import Namespace="System.Web" %>
<%@ Import Namespace="System.Web.Mail" %>
<HTML>
 <HEAD>
  <title>Mail Test</title>
 </HEAD>
  <script language="C#" runat="server">
 private void Page_Load(Object sender, EventArgs e)
 {
  try
  {
   MailMessage mailObj = new MailMessage();
   mailObj.From = "sales@joeswidgets.com";
   mailObj.To = "joesmith@someisp.com";
   mailObj.Subject = "Your Widget Order";
   mailObj.Body = "Your order was processed.";
   mailObj.BodyFormat = MailFormat.Text;
     SmtpMail.SmtpServer = "mail-fwd";
   SmtpMail.Send(mailObj);
   Response.Write("Mail sent successfully");
  }
  catch (Exception x)
  {
  Response.Write("Your message was not sent: " + x.Message);
 }
}
 </script>
 <body>
   <form id="mail_test" method="post" runat="server">
   </form>
 </body>
</HTML>

VB.NET

<%@ Import Namespace="System" %>
<%@ Import Namespace="System.Web" %>
<%@ Import Namespace="System.Web.Mail" %>
<HTML>
  <HEAD>
   <title>Mail Test</title>
  </HEAD>
   <script language="VB" runat="server">
    Sub Page_Load(sender As Object, E as EventArgs)
     Try Dim Mailer As MailMessage
     Mailer = New MailMessage()
     Mailer.From = "sales@joeswidgets.com"
     Mailer.To = "joesmith@someisp.com"
     Mailer.Subject = "Your Widget Order"
     Mailer.Body = "Your order was processed."
     Mailer.BodyFormat = MailFormat.Text
       SmtpMail.SmtpServer = "mail-fwd"
     SmtpMail.Send(Mailer)
     Response.Write("Mail sent successfully")
   Catch ex As Exception
     Response.Write("Your message was not sent: " + ex.Message)
   End Try
 End Sub
 </script>
 <body>
  <form id="mail_test" method="post" runat="server">
  </form>
 </body>
</HTML>

Q: How do I upload a file from my ASP.NET page?

A: In order to perform file upload in your ASP.NET page, you will need to use two classes: the System.Web.UI.HtmlControls.HtmlInputFile class and the System.Web.HttpPostedFile class. The HtmlInputFile class represents and HTML input control that the user will use on the client side to select a file to upload. The HttpPostedFile class represents the uploaded file and is obtained from the PostedFile property of the HtmlInputFile class. In order to use the HtmlInputFile control, you need to add the enctype attribute to your form tag as follows:

<form id="upload" method="post" runat="server" enctype="multipart/form-data">

Also, remember that the /data directory is the only directory with Write permissions enabled for the anonymous user. Therefore, you will need to make sure that the your code uploads the file to the /data directory or one of its subdirectories.

Below is a simple example of how to upload a file via an ASP.NET page in C# and VB.NET.

C#

<%@ Import Namespace="System" %>
<%@ Import Namespace="System.Web" %>
<%@ Import Namespace="System.Web.UI.HtmlControls" %>
<%@ Import Namespace="System.IO" %>
<%@ Import Namespace="System.Drawing" %>
<html>
<head>
 <title>upload_cs</title>
</head>
<script language="C#" runat="server">
 public void UploadFile(object sender, EventArgs e)
 {
  if (loFile.PostedFile != null)
  {
   try
   {
    string strFileName, strFileNamePath, strFileFolder;

    strFileFolder = Context.Server.MapPath(@"data\");
    strFileName = loFile.PostedFile.FileName;
    strFileName = Path.GetFileName(strFileName);
 

    strFileNamePath = strFileFolder + strFileName;
    loFile.PostedFile.SaveAs(strFileNamePath);

    lblFileName.Text = strFileName;
    lblFileLength.Text = loFile.PostedFile.ContentLength.ToString();
    lblFileType.Text = loFile.PostedFile.ContentType;
    pnStatus.Visible = true;
   }
   catch (Exception x)
   {
    Label lblError = new Label();
    lblError.ForeColor = Color.Red;
    lblError.Text = "Exception occurred: " + x.Message;
    lblError.Visible = true;
    this.Controls.Add(lblError);
   }
  }
 }
</script>
<body>

<form id="upload_cs" method="post" runat="server" enctype="multipart/form-data">
<P>
 <INPUT type="file" id="loFile" runat="server">
</P>
<P>
 <asp:Button id="btnUpload" runat="server" Text=" Upload " OnClick="UploadFile"></asp:Button></P>
<P>
 <asp:Panel id="pnStatus" runat="server" Visible="False">
  <asp:Label id="lblFileName" Font-Bold="True" Runat="server"></asp:Label> uploaded<BR>
  <asp:Label id="lblFileLength" Runat="server"></asp:Label> bytes<BR>
  <asp:Label id="lblFileType" Runat="server"></asp:Label>
 </asp:Panel></P>
</form>
</body>
</html>

VB.NET

<%@ Import Namespace="System" %>
<%@ Import Namespace="System.Web" %>
<%@ Import Namespace="System.Web.UI.HtmlControls" %>
<%@ Import Namespace="System.IO" %>
<%@ Import Namespace="System.Drawing" %>
<HTML>
<HEAD>
  <title>upload</title>
</HEAD>
  <script language="VB" runat="server"> Sub UploadFile(sender as Object, e as EventArgs)
   If Not (loFile.PostedFile Is Nothing) Then
    Try
     Dim strFileName, strFileNamePath, strFileFolder As String

     strFileFolder = Context.Server.MapPath("data\")
     strFileName = loFile.PostedFile.FileName
     strFileName = Path.GetFileName(strFileName)
     strFileNamePath = strFileFolder + strFileName
     loFile.PostedFile.SaveAs(strFileNamePath)

     lblFileName.Text = strFileName
     lblFileLength.Text = loFile.PostedFile.ContentLength.ToString()
     lblFileType.Text = loFile.PostedFile.ContentType
     pnStatus.Visible = True
  Catch ex As Exception
     Dim lblError As Label
     lblError = New Label()
     lblError.ForeColor = Color.Red
     lblError.Text = "Exception occurred: " + ex.Message
     lblError.Visible = True
     Page.Controls.Add(lblError)
    End Try
   End If
  End Sub
 </script>
<body MS_POSITIONING="FlowLayout">
<form id="upload" method="post" encType="multipart/form-data" runat="server">
<P><INPUT id="loFile" type="file" name="loFile" runat="server">
</P>
<P><asp:button id="btnUpload" onclick="UploadFile" runat="server" Text=" Upload "></asp:button></P> <P><asp:panel id="pnStatus" runat="server" Visible="False">
<asp:Label id="lblFileName" Runat="server" Font-Bold="True"></asp:Label>&nbsp;uploaded<BR>
<asp:Label id="lblFileLength" Runat="server"></asp:Label>bytes<BR>
<asp:Label id="lblFileType" Runat="server"></asp:Label></asp:panel></P>
</form>
</body>
</HTML>