Found 2 elements with non-unique id #__VIEWSTATE

Question

I am working on a legacy ASP.NET application that renders two forms on a single web page. Each form implements its own __VIEWSTATE field.

Since Chrome v63 duplicate field names throw an error in the console:

Found 2 elements with non-unique id #__VIEWSTATE

I don't have the luxury of rewriting the application to remove the duplicated forms. Is there another way to rename the __VIEWSTATE fields, or some other work around?

Answer 1

In Page class there are two methods that saves and loads view state. By overriding these two methods and set them to use another hidden filed you can rename __VIEWSTATE for that page.

Here's how you can do it:

public partial class SamplePage : Page
{
    const string ViewStateHiddenFiledName = "_VIEWSTATE_Page1";

    protected override void SavePageStateToPersistenceMedium(object viewState)
    {
        LosFormatter los = new LosFormatter();
        StringWriter writer = new StringWriter();

        los.Serialize(writer, viewState);

        string serilizedViewState = writer.ToString();

        ClientScript.RegisterHiddenField(ViewStateHiddenFiledName, serilizedViewState);
    }

    protected override object LoadPageStateFromPersistenceMedium()
    {
        string serilizedViewState = Request.Form[ViewStateHiddenFiledName];
        if (serilizedViewState != "")
        {
            LosFormatter los = new LosFormatter();
            return los.Deserialize(serilizedViewState);
        }
        return null;
    }
}