The Gridview 'GridView1' fired event RowEditing which wasn't handled.

If you are getting the above error, please add the following event code in the Grid view. Please  find  the example below.

OnRowEditing="GridView1_RowEditing"

Please Add the code below in Aspx.cs page for GridView1_RowEditing

Protected void GridView1_RowEditing (objectsender, GridViewEditEventArgs e)

{

      GridView1.EditIndex = -1;

      BindGridData ();

}