spgridview grouping by and Paging

// Create  myGridView object , set AllowGrouping and AllowPaging = true
SPGridView myGridView;
myGridView = new SPGridView();
myGridView.AutoGenerateColumns = false;

myGridView.AllowGrouping = true;
myGridView.AllowGroupCollapse = true;
 myGridView.GroupField = "Mission";
myGridView.PageIndexChanging += new GridViewPageEventHandler(myGridView_PageIndexChanging);
myGridView.GroupDescriptionField = "Mission";
myGridView.GroupFieldDisplayName = "Mission";
myGridView.DisplayGroupFieldName = false;
myGridView.AllowPaging = true;
myGridView.PageSize = 30;
myGridView.PageIndexChanging += new GridViewPageEventHandler(myGridView_PageIndexChanging);

 Controls.Add(myGridView);
//set PagerTemplate  to null
 myGridView.PagerTemplate = null;
// call databind method
GetDocument();