I am facing this problem
 
Unable to cast Object of type ‘ASP.MasterPage_Master’ to type ‘ASP.MasterPage_Master’
 
We use the master page with the drop down list. The value of the dropdown list is used in the content page. The developed code for this scenario is given below.
 
Main.Master.cs
 
public event CommandEventHandler SelectedIndexChangedForDDL;
 
protected void cmbActionType_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (SelectedIndexChangedForDDL != null)
            SelectedIndexChangedForDDL(this, new CommandEventArgs(cmbActionType.ClientID, cmbActionType.SelectedItem.Value.ToString()));
    }
 
 
 
Home.aspx
 
 
protected void Page_Load(object sender, EventArgs e)
{
 // Command Event SelectedIndexChangedForDDL Handler is declared in
 // Main.Master Page.
Master.SelectedIndexChangedForDDL += new 
 
CommandEventHandler(GetIndex);
       
}
 
private void GetIndex(object sender, CommandEventArgs e)
{
 
if (sender != null)
   {
 
if((e.CommandArgument.ToString() == null)||
 
 e.CommandArgument.ToString() == "")
                {
 
                    PopulateDataGrid();
                }
                else
                {
                    PopulateDataGridBasedOnDropDownSelection(Int32.Parse(e.CommandArgument.ToString()));
                }
     }
  }