C#中实现DataGrid双向排序

private void BindData() 
{ 
DataTable dt = .......; 
if(dt != null) 
{ 
DataView dv = dt.DefaultView; 
if(DataGrid1.Attributes["SortBy"] != null) 
{ 
dv.Sort = DataGrid1.Attributes["SortBy"]; 
} 

DataGrid1.DataSource = dv; 
DataGrid1.DataBind(); 
} 
} 

private void DataGridSort(object source, System.Web.UI.WebControls.DataGridSortCommandEventArgs e) 
{ 
DataGrid1.Attributes["SortBy"] = sortstr; 
this.BindData(); 

//找到排序的列，并修改把它的排序属性 

DataGridColumn clm = null; 

for(int i=0;i<DataGrid1.Columns.Count;i++) 
{ 
if(DataGrid1.Columns[i].SortExpression == e.SortExpression ) 
{ 
clm = DataGrid1.Columns[i]; 
break; 
} 
} 

if(clm == null) return; 

if(e.SortExpression.ToLower().IndexOf("desc") > 0) 
{ 
clm.SortExpression = e.SortExpression.ToLower().Replace("desc","asc"); 
} 
else 
{ 
if(e.SortExpression.ToLower().IndexOf("asc") > 0) 
{ 
clm.SortExpression = e.SortExpression.ToLower().Replace("asc","desc"); 
} 
else 
{ 
clm.SortExpression = e.SortExpression.ToLower() + " desc"; 
} 
} 
}