Object reference not set to an instance of an object

Check the textbox variable for null before using it:

TextBox rateCenterName = (TextBox)row.FindControl("txtRateCenterName");
cmd.Text.Parameters.Add("@RateCenterName", OleDbType.VarChar).Value = (rateCenterName != null) ? rateCenterName.Text : "";

textbox's name in it's properties and in the code was different

TextBox = (TextBox)row.FindControl("txtRateCenterName");
 if(rateCenterName !=null)
{
cmd.Parameters.Add("@RateCenterName", OleDbType.VarChar).Value =rateCenterName.Text;
}

check "txtRateCenterName" control is exist or not in "row"

if you are using GridView then search the TextBox control in
row.Cells[yourcellIndex]