ASP.NET Web Forms DropDownList has a SelectedValue which is invalid because it does not exist in the list of items

Question

First of all there has been questions ( DropDownList has a SelectedValue which is invalid because it does not exist in the list of items , DropDownList "has a SelectedValue

Answer 1

I had a similar problem and fixed it by adding a DataBinding method.

protected void myDDL_DataBinding(object sender, EventArgs e)
{
    if (myDDL.SelectedIndex != -1)
    {
        myDDL.SelectedIndex = 0;
    }
}

On design page...