View State Rendering

The problem in earlier versions is that the viewstate is rendered at the bottom of the page.
If the page is posted back before the entire page is loaded, the viewstate that is being submitted back to the server is incomplete and thus invalid.

This was fixed with .NET 3.5 SP1.

But You can Fix it by below Render function in earlier version of .NET

The major difference between convert.ToString() and ToString() is that,

convert.ToString() handles null but ToString() does not handles null.

Please see below two set of code:

This code will run successfully, no exception will be raised for that:

    string name = null;

    string abc = Convert.ToString(name);

Below code will give an exception, unhandled Exception:NullReferenceException

    string name = null;

    string abc = name.ToString();