Why DataTable.AccetpChanges() doesn't mark updated rows?

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C#

WinForms

Usually, I use FormClosing event to check if there is any pending change in database tables. If yes, I call the TableAdapter.Update(Datatable) method and DataTable.AcceptChanges() before exit, to commit all pending changes.

For this purpose I have a SaveData() function.

In the form's menu I've added two buttons, [Exit] button and [Save and Exit] button. The [Exit] button simply closes the form, FormClosing is fired and if necessary save current data. [Save and Exit] calls SaveData() function and closes the form, and, FormClosing if fired again.

I don't know why, but even if I called SaveData() , Datatable.GetChanges() returns always values. As far as I know, AcceptChanges() must mark all updated records.

I'm using a typed dataset object generated with V.S.

Do you know if there Is any issue with Datatable.AcceptChanges() with typed dataset?

Thanks.

//-----------------------------------
// Bussines logic class
//-----------------------------------

// retunrs true if there are pending changes in orders table
public bool OrdersChanged
{
	get
	{
		DataTable c = this.orders.GetChanges();
		return (c == null || c.Rows.Count <= 0) ? false : true;
	}
}


// commit database changes
public bool UpdateAll()
{
	try
	{
		ta_orders.Update(this.orders);
		this.orders.AcceptChanges();
	}
	catch (Exception ex)
	{
		this.last_error = ex.Message;
		return false;
	}

	return true;
}


//-----------------------------------
// Winform methods
//-----------------------------------


// this function is called from OnFormClosing's event
protected override void AditionalOnClosingActions(FormClosingEventArgs e)
{
	base.AditionalOnClosingActions(e);

	// ends any pending grid edit
	this.Validate();
	this.gridQuestions.EndUpdate();

	// ends binding source edit
	this.bl_order.bsOrders.EndEdit();

	// ask for confirmation
	if (this.bl_order.OrdersChanged)
	{
		string msg = this.Text + "\n\nSave pending changes?";
		if (MessageBox.Show(msg, "CMF", MessageBoxButtons.YesNo) == DialogResult.Yes)
		{
			SaveData();
		}
	}
}

// commit database changes
protected override bool SaveData()
{
	base.SaveData();

	bool result = false;

	try
	{
		this.Validate();

		this.bl_order.UpdateAll();

		if (this.bl_order.last_error != "")
			throw new Exception(this.bl_order.last_error);

		// refresh order's list
		SendParentRequest("refreshOrdersList", null);

		result = true;

	}
	catch (Exception ex)
	{
		MessageBox.Show(ex.Message);
	}

	return result;
}