ASP.NET Tutorial/Development/Server class

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Demonstration of Page_Error Handler

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="PageExceptionTest" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Demonstration of Page_Error Handler</title>
</head>
<body>
    <form id="form1" runat="server">
    Demonstration of Page_Error Handler. This markup will never be displayed.
    </form>
</body>
</html>
File: Default.aspx.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class PageExceptionTest : System.Web.UI.Page
{
   protected void Page_Load(object sender, EventArgs e)
   {
      BuggyMethod();   
   }
   private void BuggyMethod()
   {
      throw new ApplicationException("Your buggy code caused an exception.");
   }
   private void Page_Error(object sender, EventArgs e)
   {
      Exception ex = Server.GetLastError();
      Response.Write("<h1>An error has occurred</h1>");
      Response.Write("<h2>" + ex.Message + "</h2>");
      Response.Write("<pre>" + ex.StackTrace + "</pre>");
      Context.ClearError();
   }
}


Forward the user to the information page, with the query string data (#)

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="QueryStringSender" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:ListBox ID="lstItems" 
                     runat="server" 
                     Height="155px" 
                     Width="165px"></asp:ListBox><br />
        <br />
        <asp:CheckBox ID="chkDetails" 
                      runat="server" 
                      Text="Show full details" /><br />
        <br />
        <asp:Button ID="cmdGo" 
                    runat="server" 
                    OnClick="cmdGo_Click" 
                    Text="View Information"
            Width="165px" /><br />
        <br />
        <asp:Label ID="lblError" runat="server" EnableViewState="False"></asp:Label>
    
    </div>
    </form>
</body>
</html>

File: Default.aspx.cs

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class QueryStringSender : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    if (!this.IsPostBack)
    {
      lstItems.Items.Add("A");
      lstItems.Items.Add("B");
      lstItems.Items.Add("C");
      lstItems.Items.Add("D");
      lstItems.Items.Add("F");
    }
    }
  protected void cmdGo_Click(object sender, EventArgs e)
  {
    if (lstItems.SelectedIndex == -1)
        {
            lblError.Text = "You must select an item.";
        }
        else
        {
            string url = "NextPage.aspx?";
            url += "Item=" + Server.UrlEncode(lstItems.SelectedItem.Text) + "&";
            url += "Mode=" + chkDetails.Checked.ToString();
            Response.Redirect(url);
        }
    }
}

File: NextPage.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="NextPage.aspx.cs" Inherits="QueryStringRecipient" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:Label ID="lblInfo" runat="server" EnableViewState="False" ></asp:Label>
    </div>
    </form>
</body>
</html>

File: NextPage.aspx.cs

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class QueryStringRecipient : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        lblInfo.Text = "Item: " + Request.QueryString["Item"];
        lblInfo.Text += "<br />Show Full Record: ";
        lblInfo.Text += Request.QueryString["Mode"];
    }
}


Server.Execute

<%@ Page Language="VB" %>
<html>
<head>
   <title>Executing Another Page and Returning its Output</title>
   <script runat="server">
      Sub Execute()
         Dim Url As String = "CreateObject.aspx"
         Dim sw As New System.IO.StringWriter
         Server.Execute(Url, sw)
         Response.Write("Request output:<br/><br/>" & sw.ToString())
      End Sub
   </script>
</head>
<body>
<% Execute %>
</body>
</html>


Server.GetLastError()

<%@ Page Language="VB" %>
<html>
<head>
   <title>Examining the Last Error</title>
   <script runat="server">
      Sub CauseError(sender As Object, e As EventArgs)
         Dim x, y, z As Integer
         
         y = 1
         z = 0
         x = y / z
      End Sub
      Sub Page_Error(Source As Object, E As EventArgs)
         Dim LastError As Exception
         Dim ErrMessage As String
         LastError = Server.GetLastError()
         If Not LastError Is Nothing Then
            ErrMessage = LastError.Message
         Else
            ErrMessage = "No Errors"
         End If
         Response.Write("Last Error = " & ErrMessage & "<br/><br/>")
         Server.ClearError()
      End Sub
   </script>
</head>
<body>
   <form runat="server">
      <h4><font face="verdana">Cause an Error to Occur...</font></h4>
      <asp:button text="CauseError" OnClick="CauseError" runat="server"/>
   </form>
</body>
</html>


Server.HtmlDecode

<%@ Page Language="VB" %>
<html>
<head>
   <title>Decoding Encoded HTML Strings</title>
   <script runat="server">
      Sub HtmlDecode()
         Dim StrToDecode As String
         Dim StrToReturn As String
         StrToDecode = "&lt;p&gt;Hello, World!&lt;/p&gt;"
         StrToReturn = Server.HtmlDecode(StrToDecode)
         Response.Write(StrToReturn)
      End Sub
   </script>
</head>
<body>
<% HtmlDecode %>
</body>
</html>


Server.HtmlEncode

<%@ Page Language="VB" %>
<html>
<head>
   <title>Encoding HTML Strings</title>
   <script runat="server">
      Sub HtmlEncode()
         Dim StrToEncode As String
         Dim StrToReturn As String
         StrToEncode = "<%@ Page Language=""VB"" %>"
         StrToReturn = Server.HtmlEncode(StrToEncode)
         Response.Write(StrToReturn)
      End Sub
   </script>
</head>
<body>
<% HtmlEncode %>
</body>
</html>


Server.MachineName

<%@ Page Language="VB" %>
<html>
<head>
   <title>Accessing the MachineName Property</title>
   <script runat="server">
      Sub GetMachineName()
         Dim ServerName As String
         ServerName = Server.MachineName
         Response.Write("The name of the server is " & ServerName & ".<br>")
      End Sub
   </script>
</head>
<body>
<% GetMachineName %>
</body>
</html>


Server.MapPath

<%@ Page Language="VB" %>
<html>
<head>
   <title>Determining a Physical Path</title>
   <script runat="server">
      Sub MapPath()
         Dim RelativePath As String
         Dim PhysicalPath As String
         RelativePath = "HtmlEncode.aspx"
         PhysicalPath = Server.MapPath(RelativePath)
         Response.Write(PhysicalPath)
      End Sub
   </script>
</head>
<body>
<% MapPath %>
</body>
</html>


Server.ScriptTimeout

<%@ Page Language="VB" %>
<html>
<head>
   <title>Accessing and Modifying the ScriptTimeout Property</title>
   <script runat="server">
      Sub GetScriptTimeout()
         Dim Timeout As String
         "Server.ScriptTimeout = 120
         Timeout = Server.ScriptTimeout
         Response.Write("The current ScriptTimeout value is  " & Timeout & ".<br>")
      End Sub
   </script>
</head>
<body>
<% GetScriptTimeout %>
</body>
</html>


Server.Transfer

<%@ Page Language="VB" %>
<html>
<head>
   <title>Transferring Control to Another Page</title>
   <script runat="server">
      Sub Transfer()
         Dim Url As String = "CreateObject.aspx"
         Server.Transfer(Url)
         Response.Write("This code will never be executed!")
      End Sub
   </script>
</head>
<body>
<% Transfer %>
</body>
</html>


Server.UrlDecode

<%@ Page Language="VB" %>
<html>
<head>
   <title>Decoding Encoded URL Strings</title>
   <script runat="server">
      Sub UrlDecode()
         Dim StrToDecode As String
         Dim StrToReturn As String
         StrToDecode = Request.QueryString("StrToDecode")
         StrToReturn = Server.UrlDecode(StrToDecode)
         Response.Write(StrToReturn)
      End Sub
   </script>
</head>
<body>
<% UrlDecode %>
</body>
</html>


Server.UrlEncode

<%@ Page Language="VB" %>
<html>
   <head>
      <title>URLEncoding</title>
   <script runat="server">
      Sub Page_Load()
         If IsPostBack
            Response.Write(Server.UrlEncode(Request.Form("name")))
         End If
      End Sub
   </script>
   </head>
<body>
   <form id="form1" action="Default.aspx" method="POST" runat="server">
      <h3>Name:</h3>
      <input type="text" id="name" runat="server">
      <input type="submit" runat="server">
   </form>
</body>
</html>


Server.UrlPathEncode

<%@ Page Language="VB" %>
<html>
<head>
   <title>Encoding URL Strings</title>
   <script runat="server">
      Sub UrlPathEncode()
         Dim StrToEncode As String
         Dim StrToReturn As String
         StrToEncode = "UrlPathEncode.aspx?Arg=foo"
         StrToReturn = Server.UrlPathEncode(StrToEncode)
         Response.Write("<a href=""" & StrToReturn & """>" & StrToReturn & "</a>")
      End Sub
   </script>
</head>
<body>
<% UrlPathEncode %>
</body>
</html>


text generated by Execute can be embedded in the main response or cached in a writer object

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" 
    Inherits="Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Testing Server.Execute</title>
</head>
<body>
    <div id="pageContent">
        <form id="form1" runat="server">
            <asp:Label runat="server" ID="Label1"></asp:Label>
        </form>
    </div>
</body>
</html>
File: Default.aspx.cs
using System;
using System.Data;
using System.Configuration;
using System.IO;
using System.Web;
using System.Text;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        StringBuilder builder = new StringBuilder();
        builder.Append("<b>Response generated before Execute is called</b><hr>");
        StringWriter writer = new StringWriter();
        Server.Execute("child.aspx", writer);
        builder.Append(writer.ToString());
        builder.Append("<hr><b>Response generated after the call to Execute.</b>");
        Label1.Text = builder.ToString();
    }
}
File: child.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" 
    Inherits="Child"  %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>child.aspx</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    
    </div>
    </form>
</body>
</html>
File: child.aspx.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Text;
public partial class Child : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Response.Write("Response generated by <i>child.aspx</i>");
    }
}


Use Server.HtmlEncode to encode HTML tags (C#)

File: Default.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="HtmlEncodeTest" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
 "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form ID="form1" runat="server">
    <div>
        <h1>Properly encoded:</h1> 
        <div ID="ctrl2" runat="server"/>
        <br /><hr /><br />
        <h1>Incorrectly encoded:</h1> 
        <div ID="ctrl1" runat="server"/>
    </div>
    </form>
</body>
</html>


File: Default.aspx.cs

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class HtmlEncodeTest : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    ctrl1.InnerHtml = "To <b>bold</b> text use the <b> tag.";
    ctrl2.InnerHtml = "To <b>bold</b> text use the " + Server.HtmlEncode("<b>") + " tag.";
    }
}


Use Server.MapPath() to load the file in the current directory (VB.net)

<%@ Page Language="VB" %>
<%@ Import Namespace="System.Xml" %>
<script runat=server>
   sub Page_Load(Sender as Object, e as EventArgs)
      dim reader as XMLTextReader
         
      try
         reader = new XMLTextReader(Server.MapPath("books.xml"))
         While reader.Read()
            Response.Write("<b>" & reader.Name & "</b> " & _
                reader.Value & "<br>")
         
         End While
      catch ex as Exception
         Response.Write("Error accessing XML file")
      finally
         reader.close
      end try
   end sub
</script>
<html><body>
</body></html>
File: books.xml
<?xml version="1.0"?>
<bookstore>
  <book genre="asdf">
    <title>asdf</title>
    <author>
      <first-name>asdf</first-name>
      <last-name>asdf</last-name>
    </author>
    <price>asdf</price>
  </book>
  <book genre="asdf">
    <title>asdf</title>
    <author>
      <first-name>asdf</first-name>
      <last-name>asdf</last-name>
    </author>
    <price>asdf</price>
  </book>
  <book genre="asdf">
    <title>asdf</title>
    <author>
      <first-name>asdf</first-name>
      <last-name>asdf</last-name>
    </author>
    <price>asdf</price>
  </book>
</bookstore>


Use Server.Transfer to transfer action to another aspx file (C#)

File: Default.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="CrossPage1" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>CrossPage1</title>
</head>
<body>
    <form id="form1" runat="server" >
    <div>
        First Name:
        <asp:TextBox ID="txtFirstName" runat="server"></asp:TextBox>
        <br />
        Last Name:
        <asp:TextBox ID="txtLastName" runat="server"></asp:TextBox>
        <br />
        <br />
        <asp:Button runat="server" ID="cmdPost" 
                PostBackUrl="NextPage.aspx" Text="Cross-Page Postback" /><br />
        <asp:Button runat="server" ID="cmdTransfer" Text="Manual Transfer" OnClick="cmdTransfer_Click" Visible="False" />
    </div>
    </form>
</body>
</html>
File: Default.aspx.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class CrossPage1 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    if (Request.QueryString["err"] != null)
      Page.Validate();
    }

  protected void cmdTransfer_Click(object sender, EventArgs e)
  {
    Server.Transfer("NextPage.aspx", true);
  }
    public string FullName
    {
        get { return txtFirstName.Text + " " + txtLastName.Text; }
    }
}

File: NextPage.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="NextPage.aspx.cs" Inherits="CrossPage2" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server" >
    <div>
        <asp:Label ID="lblInfo" runat="server"></asp:Label></div>
    </form>
</body>
</html>

File: NextPage.aspx.cs

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class CrossPage2 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (PreviousPage != null)
        {
            lblInfo.Text = "You came from a page titled " +
                PreviousPage.Title + "<br />";
            CrossPage1 prevPage = PreviousPage as CrossPage1;
            if (prevPage != null)
            {
                lblInfo.Text += "You typed in this: " + prevPage.FullName +
                  "<br />";
            }
        }
    }
}
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