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Error:RegisterForEventValidation can only be called during Render
By Big | Jan 15, 2015 | In Tips | Total Views [ 2535 ]
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Sometime I get "RegisterForEventValidation can only be called during Render" error or "Control 'GridView1' of type 'GridView' must be placed inside a form tag with runat=server" error while implementing export to excel functionality in my application. Let's see what is it all about.

The Problem

I was implementing export to excel functionality in my application. I had a GridView and was using this to get data into my export to excel method. Suddenly I got this error - "Control 'GridView1' of type 'GridView' must be placed inside a form tag with runat=server". It was shocking because my grid was already in <form> tag.

    protected void ButtonExport_Click(object sender, EventArgs e)
    {
        Response.Clear();
        Response.AddHeader("content-disposition",
            string.Format("attachment;filename={0}.xls", "Order"));
        Response.Charset = "";
        Response.ContentType = "application/vnd.xls";

        StringWriter stringWrite = new StringWriter();
        HtmlTextWriter htmlWrite = new HtmlTextWriter(stringWrite);
        GridView1.RenderControl(htmlWrite);
        Response.Write(stringWrite.ToString());
        Response.End();
    }

My code was throwing rendering error. It was throwing error at "GridView1.RenderControl(htmlWrite);" line.

A quick solution

Simply add these line of code in your page and you can continue with your task without any hassle.

        public override void VerifyRenderingInServerForm(Control control)
        {
            //Leave blank
        }

Add EnableEventValidation="false" in page directive.

Hope it can help you.

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About the Author

Big
Rahul Jha (Big)
Founder, Developer dotnet-concept.com
Has working experience in different phases of Software Development Life Cycle (SDLC) in CMS, Gaming, Health Care and Financial Services domain using Agile pattern. Working experience in Design patterns, ASP.NET, MVC, Windows application, WCF, ADO.NET, SQL Server and Test Driven Development (TDD) environment with JQuery, JavaScript, N-Unit, Entity Frameworks, LINQ, Code Refactoring and Business Objects Models.

 
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