How to add buttons for fullpost back in gridview while using update panels

1)
Add following code on row_databound

ImageButton ImageButtonDocumentDownLoad = (ImageButton)e.Row.FindControl("ImageButtonDocumentDownLoad");

ScriptManager scriptManager = ScriptManager.GetCurrent(this);
scriptManager.RegisterPostBackControl(ImageButtonDocumentDownLoad);

//If grid view in user control

2)
ScriptManager scriptManager = new ScriptManager();
scriptManager.RegisterPostBackControl(ImageButtonDocumentDownLoad);

Thanks
Mahesh K. Sharma