Dynamic control id is not firing

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ASP.NET

grid

Hi ,

I have gridview and button out side. for gridview i have autogenerate columns true it was dynamicllay change as per the roles so different grids will appear.i will bind the grid structure as follows(note it might chage as per the roles)

SNo  Name     Address
1    kerrthi   hyderabad

i am showing the gridview in label and in row data bound i was doing

TextBox tb = new TextBox();
RequiredFieldValidator rfv = new RequiredFieldValidator();
tb.Text = string.Empty;
if (grvInsuranceDetails.HeaderRow.Cells[i].Text == "IE_VECHICLE_MAP") { 
    tb.Enabled = false;
    tb.Text = ViewState["IE_Vehiclecode"].ToString();
}
tb.ID = "txtbox" + i.ToString();
rfv.ID = "rfvvalid" + i.ToString();
rfv.ControlToValidate = tb.ID;
rfv.ErrorMessage = "*";
rfv.ForeColor = System.Drawing.Color.Red;
rfv.ValidationGroup = "required";
tb.Style.Add("Width", "120px");
tb.Style.Add("Height", "15px");
tb.Attributes.Add("runat", "Server");
//c.Controls.Clear();
//c.RowSpan
grdviewvechicleDetails.Controls.Add(tb);
c.Controls.Add(tb);
c.Controls.Add(rfv);
i++;

in submit button click i was not able the find the text box id it was showing as null

foreach (GridViewRow grv in grvInsuranceDetails.Rows)
            {
                int i = 0;
                   TextBox txt = (TextBox)grv.FindControl("txtbox1");
                    foreach (TableCell c in grv.Cells)
                    {
                        TextBox txt1 = (TextBox)c.FindControl("txtbox0");
                        string grdid = grvInsuranceDetails.Rows[grv.RowIndex].Cells[i].Text.ToString().TrimEnd();
                        i++;
                    }
            } 

Can anybody help me with this?

Thanks in advance!