Sorting a Grid column on header click

i had a small requirement to sort a grid column when column header is clicked .
Here is what i did

a) Enable allowsorting Property in grid-view

<asp:GridView ID="GridView1" runat="server" CellPadding="3" GridLines="Horizontal"

   Font-Names="Verdana" Font-Size="10" DataKeyNames="Tenant_Name"

   AutoGenerateColumns="false" AllowSorting="true"

        onselectedindexchanged="GridView1_SelectedIndexChanged"

        onrowcancelingedit="GridView1_RowCancelingEdit"

        onrowcreated="GridView1_RowCreated" onrowediting="GridView1_RowEditing"

        onrowupdated="GridView1_RowUpdated" onrowupdating="GridView1_RowUpdating"

        onrowdeleted="GridView1_RowDeleted" onrowdeleting="GridView1_RowDeleting"

        onrowdatabound="GridView1_RowDataBound" onsorting="GridView1_Sorting" 

   >

add Property SortExpression

      <asp:BoundField DataField="Tenant_Name" HeaderText="Tenant Name" ReadOnly="true" SortExpression="Tenant_Name" />

b) Create a Property  for sort direction and store in a view state

  public SortDirection dir

    {
        get

        {

            if (ViewState["dirState"] == null)

            {

                ViewState["dirState"] = SortDirection.Ascending;

            }

            return (SortDirection)ViewState["dirState"];

        }
        set


        {

            ViewState["dirState"] = value;

        }

    }


c) if data is stored in dataset copy dataset to datatable

 dt = dsshowTen.Tables[0];

d) add event  GridView1_Sorting(object sender, GridViewSortEventArgs e) event 

   

            string sortingDirection = string.Empty;

        if (dir == SortDirection.Ascending)

        {

            dir = SortDirection.Descending;

            sortingDirection = "Desc";

        }

        else

        {

            dir = SortDirection.Ascending;

            sortingDirection = "Asc";

        }

       

        DataView sortedView = new DataView(dt);

        sortedView.Sort = e.SortExpression + " " + sortingDirection;

        GridView1.DataSource = sortedView;

        GridView1.DataBind();

the above 2 screenshot shows sorted records of Tenant_Name column