gridview寻找控件方法,该如何处理_ASP.NET

gridview寻找控件方法
我在HeaderTemplate中放了一个dropdownlist控件，请问下怎么在除gridview_RowDataBound方法以外的地方获取该控件的对象

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GridView.Rows[i].FindControl("XXX")
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foreach (GridViewRow gr in gridView.Rows)
{
HiddenField hf=gr.FindControl("hf") as HiddenField;
if(hf!=null)
{
//
}
}

------解决方案--------------------------------------------------------

C# code

dropdownlist ddl = (dropdownlist)e.Row.Cells[3].FindControl("dropdownlist");
------解决方案--------------------------------------------------------
  foreach (GridViewRow r in this.GridView1.Rows)
       {
           DropDownList ddl = r.FindControl("id") as DropDownList ;
       }
------解决方案--------------------------------------------------------
C# code        DropDownList ddl = this.GridView1.HeaderRow.FindControl("DropDownList1") as DropDownList;