在RowCreated事件中添加TableHeaderCell时，允许在gridview中不工作

Question

我想允许在GridView中的字段（日期）中进行排序。但即使我添加AllowSorting =“true”和SortExpression，它的标题文本也不会更改为超链接。我在其创建的行事件中添加了gridview的标题文本。因为我想合并单元格和行。这是问题吗？

  <asp:GridView 
         ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="student_id"                           
         onrowdatabound="GridView1_RowDataBound" onrowcreated="GridView1_RowCreated" 
         AllowSorting="true" OnSorting="GridView1_Sorting">             

                        <Columns>
                            <asp:TemplateField HeaderText="S/no" >
                                <ItemTemplate>
                                    <%# ((GridViewRow)Container).RowIndex + 1%>
                                </ItemTemplate>
                            </asp:TemplateField>
                            <asp:BoundField DataField="get_date" ItemStyle-Width="110px" HeaderText="Date" DataFormatString="{0:d}"
                                ReadOnly="True" SortExpression="get_date" >
                            </asp:BoundField>
                             <asp:BoundField DataField="student_id"  HeaderText="Student ID" 
                                ReadOnly="True"  >
                            </asp:BoundField>
                             <asp:BoundField DataField="previous_student_id" HeaderText="Previous ID" 
                                ReadOnly="True"  >                                 
                            </asp:BoundField>
                               <asp:BoundField DataField="score_english" HeaderText="English" 
                                ReadOnly="True"  >                                 
                            </asp:BoundField>
                            <asp:BoundField DataField="score_science" HeaderText="Science" 
                                ReadOnly="True"  >                                 
                            </asp:BoundField>
                                  <asp:BoundField DataField="mark" HeaderText="Marks" 
                                ReadOnly="True"  >                                 
                            </asp:BoundField>

                        </Columns> 
                    </asp:GridView>

 protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{

    // Invisibling the columns of second row header (normally created on binding)
    if (e.Row.RowType == DataControlRowType.Header)
    {
        e.Row.Cells[0].Visible = false; // Invisibiling s/no Header Cell
        e.Row.Cells[1].Visible = false; 
        e.Row.Cells[2].Visible = false; 
        e.Row.Cells[3].Visible = false; 
        e.Row.Cells[6].Visible = false; 
    }
   }

   protected void GridView1_RowCreated(object sender, GridViewRowEventArgs e)
{

    // Adding a column manually once the header created
    if (e.Row.RowType == DataControlRowType.Header) // If header created
    {
        GridView DSGrid = (GridView)sender;

        // Creating a Row
        GridViewRow HeaderRow1 = new GridViewRow(0, 0, DataControlRowType.Header, DataControlRowState.Insert);
        GridViewRow HeaderRow = new GridViewRow(1, 0, DataControlRowType.Header, DataControlRowState.Insert);

        //Adding first header
        TableHeaderCell HeaderCell1 = new TableHeaderCell();
        HeaderCell1.Text = "Student Details";
        HeaderCell1.HorizontalAlign = HorizontalAlign.Center;
        HeaderCell1.ColumnSpan =7;

        HeaderRow1.Cells.Add(HeaderCell1);

        //Adding S/no Column
        TableHeaderCell HeaderCell = new TableHeaderCell();
        HeaderCell.Text = "S/no";
        HeaderCell.HorizontalAlign = HorizontalAlign.Center;
        HeaderCell.RowSpan = 2; // For merging first, second row cells to one
        HeaderRow.Cells.Add(HeaderCell);

        //Adding Date Column
        HeaderCell = new TableHeaderCell();
        HeaderCell.Text = "Date";


        HeaderCell.HorizontalAlign = HorizontalAlign.Center;
        HeaderCell.RowSpan = 2;
        HeaderRow.Cells.Add(HeaderCell);

        //Adding Student ID Column
        HeaderCell = new TableHeaderCell();
        HeaderCell.Text = "Student ID";
        HeaderCell.HorizontalAlign = HorizontalAlign.Center;
        HeaderCell.RowSpan = 2;
        HeaderRow.Cells.Add(HeaderCell);

        //Adding Previous ID Column
        HeaderCell = new TableHeaderCell();
        HeaderCell.Text = "Previous ID";
        HeaderCell.HorizontalAlign = HorizontalAlign.Center;
        HeaderCell.RowSpan = 2;
        HeaderRow.Cells.Add(HeaderCell);

        //Adding Subject
        HeaderCell = new TableHeaderCell();
        HeaderCell.Text = "Subject";
        HeaderCell.HorizontalAlign = HorizontalAlign.Center;
        HeaderCell.ColumnSpan = 2; // For merging two columns (English,Science)
        HeaderRow.Cells.Add(HeaderCell);

        //Adding Score Column
        HeaderCell = new TableHeaderCell();
        HeaderCell.Text = "Score";
        HeaderCell.HorizontalAlign = HorizontalAlign.Center;
        HeaderCell.RowSpan = 2;
        HeaderRow.Cells.Add(HeaderCell);

        //Adding the Row at the 0th position (first row) in the Grid
        DSGrid.Controls[0].Controls.AddAt(0, HeaderRow1);
        //Adding the Row at the 1st position (second row) in the Grid
        DSGrid.Controls[0].Controls.AddAt(1, HeaderRow);
    }

}