Solution of Validation of viewstate MAC failed

Validation of viewstate MAC failed / The state information is invalid for this page and might be corrupted

so, all you need on an *.aspx page for generating this error:

Any DataSource Control (SqlDataSource, XmlDataSource…)
GridView bound / unbound to DataSource
Using DataKeyNames in GridView
Using elements
Something on the *.aspx page which takes a while till rendered (as for example banners, external pictures etc.)

One solution to this problem

Create a small class called BasePage that fixes the issues, so you just have to extend your page from BasePage instead of Page:

public class BasePage : Page
private static string[] aspNetFormElements = new string[]

protected override void Render(HtmlTextWriter writer)
StringWriter stringWriter = new StringWriter();
HtmlTextWriter htmlWriter = new HtmlTextWriter(stringWriter);
string html = stringWriter.ToString();
int formStart = html.IndexOf(“= 0)
endForm = html.IndexOf(“>”, formStart);

if (endForm >= 0)
StringBuilder viewStateBuilder = new StringBuilder();
foreach (string element in aspNetFormElements)
int startPoint = html.IndexOf(“= 0 && startPoint > endForm)
int endPoint = html.IndexOf(“/>”, startPoint);
if (endPoint >= 0)
endPoint += 2;
string viewStateInput = html.Substring(startPoint, endPoint – startPoint);
html = html.Remove(startPoint, endPoint – startPoint);

if (viewStateBuilder.Length > 0)
viewStateBuilder.Insert(0, “\r\n”);
html = html.Insert(endForm + 1, viewStateBuilder.ToString());


for more details refer


~ by UTS on May 17, 2009.

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