Drop down list binding with selected index true during row editing of grid view / Data grid

<asp:TemplateColumn HeaderText="Role">
<ItemStyle Wrap="False" BorderWidth="1px"></ItemStyle>
<ItemTemplate>
<asp:Label ID="lblRoleName" runat="server" Text='<%# Eval("RoleName") %>'></asp:Label>
</ItemTemplate>
<FooterStyle HorizontalAlign="Center"></FooterStyle>
<FooterTemplate>
<asp:DropDownList ID="add_RoleName" runat="server" DataSource='<%# getdata("PR_SelectRoleMaster") %>'
DataTextField="RoleName" DataValueField="RoleId">
</asp:DropDownList>
<font size="1" color="red">*</font>
</FooterTemplate>
<EditItemTemplate>
<asp:DropDownList ID="ddlRoleName" runat="server" OnPreRender="SetDropDownIndex"
DataSource='<%# getdata("PR_SelectRoleMaster") %>' DataTextField="RoleName" DataValueField="RoleId">
</asp:DropDownList>
</EditItemTemplate>
</asp:TemplateColumn>

string strMemberRoleName = string.Empty, strRemarkFrequency = string.Empty, strRemarksSelectionType = string.Empty;
    string strRemarksClassName = string.Empty;


In CS page

  public void SetDropDownIndex(object sender, System.EventArgs e)
    {
        System.Web.UI.WebControls.DropDownList ed;
        ed = (System.Web.UI.WebControls.DropDownList)sender;
        ed.SelectedIndex = -1;
        ed.SelectedIndex = ed.Items.IndexOf(ed.Items.FindByText(strMemberRoleName));
    }


  protected void DataGridRemarkMaster_EditCommand(object source, DataGridCommandEventArgs e)
    {
        lblRemarkMasterMsg.Text = "";
        DataGridRemarkMaster.ShowFooter = false;
        DataGridRemarkMaster.EditItemIndex = e.Item.ItemIndex;

        strMemberRoleName = ((Label)e.Item.FindControl("lblRoleName")).Text.Trim();
        strRemarkFrequency = ((Label)e.Item.FindControl("lblRemarkFrequency")).Text.Trim();
        strRemarksSelectionType = ((Label)e.Item.FindControl("lblRemarkType")).Text.Trim();
        strRemarksClassName = ((Label)e.Item.FindControl("lblClassName")).Text.Trim();

 }