Adding Sorting image (up down arrow) while sorting grid view asp.net 2.0

This article shows code how to show toggle image according to sort direction while gridview sorting.


//save column name in a view state
Protected Sub gvContentList_Sorting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewSortEventArgs) Handles gvContentList.Sorting


ViewState.Add("colname", e.SortExpression)


End Sub



Protected Sub gvContentList_RowCreated(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs) Handles gvContentList.RowCreated
Dim defaultsortimage As New Image
defaultsortimage.ImageUrl = "~/images/tbl_ascend_ord.gif"
If e.Row.RowType = DataControlRowType.Header Then
If ViewState("exp") <> "" Then
AddSortImage(e.Row)
Else
e.Row.Cells(0).Controls.Add(defaultsortimage)
End If
End If
End Sub

Public Sub AddSortImage(ByVal headerrow As GridViewRow)
Dim nColumnindex As Integer
Dim sortimage As New Image
Dim sortdirection As String
nColumnindex = getsortcolumnindex(ViewState("colname").ToString())
sortdirection = ViewState("colname").ToString + ".asc"
If ViewState("exp") = sortdirection Then
'sortimage.ImageUrl = "~/images/tbl_ascend_ord.gif"
headerrow.Cells(nColumnindex).CssClass = "sortascheaderstyle"
Else
'sortimage.ImageUrl = "~/images/tbl_descend_ord.gif"
headerrow.Cells(nColumnindex).CssClass = "sortdescheaderstyle"
End If
End Sub


Public Function getsortcolumnindex(ByVal strcol As String)
For Each field As DataControlField In gvContentList.Columns
If field.SortExpression = strcol Then
Return gvContentList.Columns.IndexOf(field)
End If

Next
Return -1
End Function