Fixing Form Action on UrlRewrite

IF you’re rewriting URL’s, you’ve probably come across the same problem I had.

When posting back on the page, the real URL is used.. this is a real pain if you’re writing a page which uses the RawUrl to serve up relevant content.

I had a good look around the web for a solution. These ranged from creating a custom HtmlForm control to replacing the form tag in the App_Browsers folder.

The following is simple and worked for me.

Place the following code in the Page_Load of the page you’re serving up.


Orginal :

Another and good way to do this using adding a browserfile to App_Browser and write an adapter.
If you do this you dont need to add any code in your pages Page_Load’s

Browser file content:

  <browser refID="Default">
      <adapter controlType="System.Web.UI.HtmlControls.HtmlForm"
               adapterType="FormRewriterControlAdapter" />

Rewriter.cs code:

using System;
using System.Data;
using System.Configuration;
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;
/// <summary>
/// Summary description for FormRewriter
/// </summary>
public class FormRewriterControlAdapter : System.Web.UI.Adapters.ControlAdapter
    protected override void Render(System.Web.UI.HtmlTextWriter writer)
        base.Render(new RewriteFormHtmlTextWriter(writer));
public class RewriteFormHtmlTextWriter : HtmlTextWriter
    public RewriteFormHtmlTextWriter(HtmlTextWriter writer)
        : base(writer)
        this.InnerWriter = writer.InnerWriter;
    public RewriteFormHtmlTextWriter(System.IO.TextWriter writer)
        : base(writer)
        base.InnerWriter = writer;
    public override void WriteAttribute(string name, string value, bool fEncode)
        // If the attribute we are writing is the "action" attribute, and we are not on a sub-control,
        // then replace the value to write with the raw URL of the request - which ensures that we'll
        // preserve the PathInfo value on postback scenarios
        if ((name == "action"))
            HttpContext Context;
            Context = HttpContext.Current;
            if (Context.Items["ActionAlreadyWritten"] == null)
                // Because we are using the HttpModule, we will use the
                // Request.RawUrl property within ASP.NET to retrieve the origional URL
                // before it was re-written. You'll want to change the line of code below
                // if you use a different URL rewriting implementation.
                value = Context.Request.RawUrl;
                // Indicate that we've already rewritten the <form>'s action attribute to prevent
                // us from rewriting a sub-control under the <form> control
                Context.Items["ActionAlreadyWritten"] = true;
        base.WriteAttribute(name, value, fEncode);
Based on :

About bpostaci
Escalation Engineer in Microsoft.

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