Implement datetime (and other) sorting in ASP.NET gridview

We need some code to load data into the table, then we use the following functions (also add the gridView_Sorting function to handle the OnSorting event of the grid, in the gridview definition in the .aspx file (OnSorting="gridView_Sorting"), same for OnPageIndexChanging event: OnPageIndexChanging="gridView_PageIndexChanging").

   1:  static SortDirection lastSortDirection = SortDirection.Ascending;

   2:  static DataTable roadmapTable;

   3:   

   4:  static string ConvertSortDirectionToSql(SortDirection sortDirection)

   5:  {

   6:      string m_SortDirection = String.Empty;

   7:   

   8:      switch (sortDirection)

   9:      {

  10:      case SortDirection.Ascending:

  11:          m_SortDirection = "ASC";

  12:          break;

  13:   

  14:      case SortDirection.Descending:

  15:          m_SortDirection = "DESC";

  16:          break;

  17:      }

  18:   

  19:      return m_SortDirection;

  20:  }

  21:   

  22:  protected void gridView_PageIndexChanging(object sender, GridViewPageEventArgs e)

  23:  {

  24:      roadmapGridView.PageIndex = e.NewPageIndex;

  25:      roadmapGridView.DataBind();

  26:  }

  27:   

  28:  protected void gridView_Sorting(object sender, GridViewSortEventArgs e)

  29:  {

  30:      if (roadmapTable == null)

  31:      {

  32:          return;

  33:      }

  34:   

  35:      lastSortDirection = lastSortDirection == SortDirection.Ascending ? SortDirection.Descending : SortDirection.Ascending;

  36:   

  37:      DataView m_DataView = new DataView(roadmapTable);

  38:      m_DataView.Sort = e.SortExpression + " " + ConvertSortDirectionToSql(lastSortDirection);

  39:      roadmapGridView.DataSource = m_DataView;

  40:      roadmapGridView.DataBind();

  41:  }