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HttpRequest.Filter Property

Gets or sets the filter to use when reading the current input stream.

Namespace:  System.Web
Assembly:  System.Web (in System.Web.dll)
public Stream Filter { get; set; }

Property Value

Type: System.IO.Stream
A Stream object to be used as the filter.
ExceptionCondition
HttpException

The specified Stream is invalid.

The following code example creates two new classes, QQQ1 and QQQ2 that filter the InputStream. Put the classes into the Global.asax file in an ASP.NET application's directory so that all input for all ASP.NET Web pages in the application will be filtered.

<%@ Page language="c#" %>
<%@ Import namespace="System.Text" %>
<%@ Import namespace="System.IO" %>

<script runat="server">

// This code is to be added to a Global.asax file. 

public void Application_BeginRequest() 
{
   Request.Filter = new QQQ1(Request.Filter);
   Request.Filter = new QQQ2(Request.Filter);
}

class QQQ1 : Stream
{
    private Stream _sink;

    public QQQ1(Stream sink)
    {
        _sink = sink;
    }

    public override bool CanRead
    {
        get { return true; }
    }

    public override bool CanSeek
    {
        get { return false; }
    }

    public override bool CanWrite
    {
        get { return false; }
    }

    public override long Length
    {
        get { return _sink.Length; }
    }

    public override long Position
    {
        get { return _sink.Position; }
        set { throw new NotSupportedException(); }
    }

    public override int Read(byte[] buffer, int offset, int count)
    {
	int c = _sink.Read(buffer, offset, count);

        for (int i = 0; i < count; i++)
        {
            if (buffer[offset+i] >= 'a' && buffer[offset+i] <= 'z')
                buffer[offset+i] -= ('a'-'A');
        }

        return c;
    }

    public override long Seek(long offset, System.IO.SeekOrigin direction)
    {
        throw new NotSupportedException();
    }

    public override void SetLength(long length)
    {
        throw new NotSupportedException();
    }

    public override void Close()
    {
        _sink.Close();
    }

    public override void Flush()
    {
        _sink.Flush();
    }

    public override void Write(byte[] buffer, int offset, int count)
    {
	throw new NotSupportedException();
    }
}

class QQQ2 : Stream
{
    private Stream _sink;

    public QQQ2(Stream sink)
    {
        _sink = sink;
    }

    public override bool CanRead
    {
        get { return true; }
    }

    public override bool CanSeek
    {
        get { return false; }
    }

    public override bool CanWrite
    {
        get { return false; }
    }

    public override long Length
    {
        get { return _sink.Length; }
    }

    public override long Position
    {
        get { return _sink.Position; }
        set { throw new NotSupportedException(); }
    }

    public override int Read(byte[] buffer, int offset, int count)
    {
	int c = _sink.Read(buffer, offset, count);

        for (int i = 0; i < count; i++)
        {
            if (buffer[i] == 'E')
                buffer[i] = (byte)'*';
            else if (buffer[i] == 'e')
                buffer[i] = (byte)'#';
        }
        return c;
    }

    public override long Seek(long offset, System.IO.SeekOrigin direction)
    {
        throw new NotSupportedException();
    }

    public override void SetLength(long length)
    {
        throw new NotSupportedException();
    }

    public override void Close()
    {
        _sink.Close();
    }

    public override void Flush()
    {
        _sink.Flush();
    }

    public override void Write(byte[] buffer, int offset, int count)
    {
	throw new NotSupportedException();
    }
}


/*____________________________________________________________________

This ASP.NET page uses the request filter to modify all text sent by the 
browser in Request.InputStream. To test the filter, use this page to take
the POSTed output from a data entry page using a tag such as: 
<form method="POST" action="ThisTestPage.aspx">


<%@ PAGE LANGUAGE = C# %>
<%@ IMPORT namespace="System.IO" %>

<html>
<Script runat=server>
   void Page_Load()
   {

      // Create a Stream object to capture entire InputStream from browser.
      Stream str = Request.InputStream;

      // Find number of bytes in stream.
      int strLen = (int)str.Length;

      // Create a byte array to hold stream.
      byte[] bArr = new byte[strLen];

      // Read stream into byte array.
      str.Read(bArr,0,strLen);

      // Convert byte array to a text string.
      String strmContents="";
      for(int i = 0; i < strLen; i++)
         strmContents = strmContents + (Char)bArr[i];

      // Display filtered stream in browser.
      Response.Write("Contents of Filtered InputStream: <br>" + strmContents);
   }
______________________________________________________________________*/

</script>

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0
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