GridView - set width of column in code behind (AutoGenerateColumns="true")

My GridView :

<asp:GridView ID="GridView1" runat="server"
    OnRowDataBound="GridView1_RowDataBound"
    AutoGenerateColumns="true"
    DataKeyNames="Role_id">
</asp:GridView>

In code behind :

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.Header)
    {
       //e.Row.Cells[2].Width = 120;                      // isn't working....
    }
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        e.Row.Cells[2].Width = new Unit(120);             // isn't working....
        TableCell cell = e.Row.Cells[2];
        cell.HorizontalAlign = HorizontalAlign.Right;           //**** does work!
        cell.BackColor = Color.LightGray;                       //**** does work!
        //cell.Width = 120;                               // isn't working....
        //e.Row.Cells[2].Width = new Unit("120px") ;      // isn't working....
        //e.Row.Cells[2].CssClass = "myGV_Cell_Width";    // isn't working....
    }
}

The GridView is populated successfully.
Notice that I can set the alignment and the backcolor of the column, but not its width.
I tried many solutions circulating around but none worked.
It always resizes the column to the longest content.
Can it be done at all...?

I was able to do it with the RowCreated event but I had to set the width of the grid and also set the grid to a table-layout:fixed

<asp:GridView ID="GridView1" runat="server"
    style="table-layout:fixed;" Width="1000px"
    OnRowCreated = "GridView1_RowCreated"
    OnRowDataBound="GridView1_RowDataBound"
    AutoGenerateColumns="true"
    DataKeyNames="Role_id">
</asp:GridView>

protected void GridView1_RowCreated(object sender, GridViewRowEventArgs e)
{

 e.Row.Cells[0].Width = New Unit("220px");

}