How to add the Preview button to the grid

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C#

ASP.NET

Hi,
I have a RadGrid which perform insert,edit and delete operations and i create a form in usercontrols and now i want to implement the preview option for the grid that means if we click on preview button the form will be opened but not editable.i create the onitemcommad event for it.

protected void gvComplaints_OnItemCommand(object sender, GridCommandEventArgs e)
       {
           if (e.CommandArgument == "Preview")
           {
               Edit = false;
               Session["Edit"] = Edit;
               int gvComplaintId = Convert.ToInt32(e.Item.OwnerTableView.DataKeyValues[e.Item.ItemIndex]["ComplaintId"]);
               Session["ComplaintId"] = gvComplaintId;
           }
           else if (e.CommandArgument == "Edit")
           {
               Edit = true;
               Session["Edit"] = Edit;
               int gvComplaintId = Convert.ToInt32(e.Item.OwnerTableView.DataKeyValues[e.Item.ItemIndex]["ComplaintId"]);
               Session["ComplaintId"] = gvComplaintId;

           }
       }

But it didnt work can anyone help me?