Sorting using Dropdownlist with Gridview

//Dropdownlist selected value changed event. This can be done on button click event also.
protected void DropDownList1_SelectIndexChanged(object sender, EventArgs e)        {
    gvSorting.Sort(DropDownList1.SelectedValue, SortDirection.Ascending);        
}

//Gridview sort command
protected void gvSorting_Sorting(object sender, GridViewSortEventArgs e)
{
    DataTable dtSortTable = gvSorting.DataSource as DataTable;
    if (dtSortTable != null)
    {
        DataView dvSortedView = new DataView(dtSortTable);
        dvSortedView.Sort = e.SortExpression + " " + getSortDirectionString(e.SortDirection);
        gvSorting.DataSource = dvSortedView;
        gvSorting.DataBind();
    }
}

//Getting the sort direction
private static string getSortDirectionString(SortDirection sortDireciton)
{
    string newSortDirection = String.Empty;
    if (sortDireciton == SortDirection.Ascending)
    {
        newSortDirection = "ASC";
    }
    else
    {
        newSortDirection = "DESC";
    }
    return newSortDirection;
}