Binding bind=new Binding("Value",tarRow,"ID_pi");
cbpiN.DataBindings.Add(bind);
bind.Format +=new ConvertEventHandler(bind_Format);
bind.Parse  +=new ConvertEventHandler(bind_Parse);

private void bind_Parse(object sender, ConvertEventArgs e)
{
if(e.DesiredType == typeof(DBNull)) 
{
	e.Value = 0;
}
}

private void bind_Format(object sender, ConvertEventArgs e)
{
if(e.DesiredType == typeof(DBNull)) 
{
	e.Value = 0;
}
}

AgentMan.dsMain.TariffRow tarRow;///!!!
...
...
...
Binding bind=new Binding("Value",tarRow,"ID_pi");
bind.Format +=new ConvertEventHandler(bind_Format);
bind.Parse  +=new ConvertEventHandler(bind_Parse);			
cbpiN.DataBindings.Add(bind);
...
...
...
private void bind_Parse(object sender, ConvertEventArgs e)
{
if(e.DesiredType == typeof(DBNull)) 
{
	e.Value=(Convert.IsDBNull(e.Value)) ? 0 : e.Value;
}
}

private void bind_Format(object sender, ConvertEventArgs e)
{
if(e.DesiredType == typeof(DBNull)) 
{
	e.Value = 0;				
}
}

if (this.dRow["..."]==System.DBNull.Value) 
this.dRow["..."]=System.DBNull.Value.ToString(); 

private void btnEditTariff_Click(object sender, System.EventArgs e)
{
bool IsNewRow=(((Button)sender).Name!=btnEditTariff.Name);
try
{
AgentMan.dsMain.TariffRow editTariffRow;

if (IsNewRow)
{
editTariffRow=this.dsMain1.Tariff.NewTariffRow();
//////Значения по умолчанию
editTariffRow.tarDF=DateTime.Today;
editTariffRow.tarDT=DateTime.Today;				
}
else
{
editTariffRow=((AgentMan.dsMain.TariffRow)((DataRowView)this.grdTariff.BindingContext[this.grdTariff.DataSource, this.grdTariff.DataMember].Current).Row);								  
editTariffRow.BeginEdit();				
}
	
frmEditTariff frmET=new frmEditTariff();
frmET.DialogParam(this.dsMain1,editTariffRow);				

frmET.ShowDialog(this);
if (frmET.DialogResult==DialogResult.OK)	
{					
if (IsNewRow) 
{
  this.dsMain1.Tariff.AddTariffRow(editTariffRow);			
}

editTariffRow.EndEdit();						
this.grdTariff.BindingContext["Tariff"].EndCurrentEdit();
dml.UpdateTableData(dsMain1.Tariff,dml.sdaTariff);			
} 
else
editTariffRow.CancelEdit();
frmET.Dispose();
}
catch (System.Exception eEndEdit)
{
System.Windows.Forms.MessageBox.Show(eEndEdit.Message);
}

public bool UpdateTableData(DataTable dtParam,System.Data.SqlClient.SqlDataAdapter sdaParam)
{
bool result=true;
try
{
sdaParam.Update(dtParam);
dtParam.AcceptChanges();
}
catch (System.Exception e)
{
dtParam.RejectChanges(); // <-- Тебе за это спасибо! :)
System.Windows.Forms.MessageBox.Show(e.Message,"Ошибка.");
result=false;
}
return result;
}

public void DialogParam(AgentMan.dsMain dsParam,AgentMan.dsMain.TariffRow tarRow)
{
this.ds1=dsParam;
this.CurrenttarRow=tarRow;
//AgentMan.dsMain.TariffDataTable tarRow=ds1.Tariff;


this.cbpiN.DataSource=dwProgIns;
this.cbzoneN.DataSource=ds1.Zones;

this.cbcurN.DataSource=ds1.Currency;
this.cbriskN.DataSource=ds1.Risk;
this.cbcurNInsure.DataSource=ds1.Currency;
this.cbtpN.DataSource=ds1.TypePeriod;
this.dwProgIns.Table=ds1.ProgIns;
this.cbtpN	.DataBindings.Add(new System.Windows.Forms.Binding("Value", tarRow, "ID_tp"));
this.cbriskN.DataBindings.Add(new System.Windows.Forms.Binding("Value", tarRow, "ID_risk"));
this.cbcurNInsure.DataBindings.Add(new System.Windows.Forms.Binding("Value", tarRow, "ID_curInsure"));
this.cbcurN	.DataBindings.Add(new System.Windows.Forms.Binding("Value", tarRow, "ID_cur"));


this.cbzoneN.DataBindings.Add(new System.Windows.Forms.Binding("Value",tarRow,"ID_zone"));
this.cbpiN	.DataBindings.Add(new System.Windows.Forms.Binding("Value",tarRow,"ID_pi"));
this.dptarDF.DataBindings.Add(new System.Windows.Forms.Binding("Value",tarRow,"tarDF"));
this.dptarDT.DataBindings.Add(new System.Windows.Forms.Binding("Value",tarRow,"tarDT"));
this.edtarSInsure.DataBindings.Add("Text",tarRow,"tarSInsure");
this.edtarSTariff.DataBindings.Add("Text",tarRow,"tarSTariff");

/// <NULLS>
this.chbID_piISNull.Checked=tarRow["ID_pi"]==System.DBNull.Value;
this.chbID_zoneISNull.Checked=tarRow["ID_zone"]==System.DBNull.Value ;
}