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Editorial Team
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Asked: 2026-05-18T21:08:57+00:00

I am using Ajax Control Toolkit 3.5. I have a form like this: <body>

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I am using Ajax Control Toolkit 3.5. I have a form like this:

<body>
<form id="form1" runat="server">
<asp:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server">
</asp:ToolkitScriptManager>
<div>
    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
        <ContentTemplate>
            <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />
            <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
        </ContentTemplate>
    </asp:UpdatePanel>
</div>
</form>

And related codebehind of this page is this:

protected void Button1_Click(object sender, EventArgs e)
{
    Label1.Text = TextBox1.Text;
}

When I write for example “foo” into the TextBox1 it succesfully copies that into Label1. But if I write any text into the textbox with some HTML tags like “<b>foo</b>” i get following Javascript error in IE statusbar:

alt text

How can I solve this?

Thanks in advance.

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1 Answer

  1. Editorial Team

    Just after posting this question, the idea of taking the form fields out of UpdatePanel and retrying the same operation came to my mind. Bingo! It throws the following exception:

        A potentially dangerous Request.Form value was detected from the client (TextBox1="<b>foo</b>"). 
Description: Request Validation has detected a potentially dangerous client input value, and processing of the request has been aborted. This value may indicate an attempt to compromise the security of your application, such as a cross-site scripting attack. You can disable request validation by setting validateRequest=false in the Page directive or in the configuration section. However, it is strongly recommended that your application explicitly check all inputs in this case. 

Exception Details: System.Web.HttpRequestValidationException: A potentially dangerous Request.Form value was detected from the client (TextBox1="<b>foo</b>").

    After seeing this error, adding the following code to the <%@ Page %> section of the page solved the problem.

    ValidateRequest="false"

    Hope this helps to others…

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