column does not allow nulls

Hi
I am working on data entry Form. This Form has several textbox fields and
two combo Box. All the textbox and these ComboBoxes which have four items are
bind to the fields in the same table in SQL server. Please take look at the
following codes and tell me why I am getting “titlecolumn does not allow
nulls”. All the fields and comboboxes have a value.
Note: I am new to C#.Net. Please send me code sample when respond to this
question. Thanks very much. God bless


Load function

this.sqlDataAdapter1.Fill(this.DataSet1);
this.BindingContext[this.DataSet1, "Patfo"].AddNew();


Save button:

try
{
this.BindingContext[this.DataSet1, "Patfo"].EndCurrentEdit();
this.sqlDataAdapter1.Update(this.DataSet1);
}
catch(System.Exception Ex)
{
MessageBox.Show(Ex.Message);