Open the dataset in the Dataset Designer by double-clicking the NorthwindDataSet.xsd file in the DataAccessTier project in Solution Explorer.

Double-click the OrderDate column of the Orders table in the designer. This action creates the ColumnChanging event handler.

Note:
The Dataset Designer does not automatically create an event handler for the C# event. The code that is required to handle the event in C# is included later in this procedure. SampleColumnChangingEvent is created and then subscribes to the ColumnChanging event in the EndInit method.

Add code to verify that e.ProposedValue for the OrderDate column contains the current date or earlier. If the proposed value is not valid, set the column to indicate that it contains an error.

The following code example validates that the OrderDate column contains the current date or earlier. If the OrderDate value is a date later than today, the OrderDate column is set to an error. The Else clause clears the error if the OrderDate is today or earlier.

Paste the Visual Basic code into the ColumnChanging event handler. Paste the C# code into the OrdersDataTable partial class declaration.

If (e.Column.ColumnName = Me.OrderDateColumn.ColumnName) Then
    If CType(e.ProposedValue, DateTime) > Today Then
        e.Row.SetColumnError(e.Column, "OrderDate cannot be in the future")
    Else
        e.Row.SetColumnError(e.Column, "")
    End If
End If

// Replace the NorthwindDataSet partial class with the following:
public partial class NorthwindDataSet
{
    partial class OrdersDataTable
    {
        public override void EndInit()
        {
            base.EndInit();
            // Configure the ColumnChanging event
            // to call the SampleColumnChangingEvent method.
            ColumnChanging += SampleColumnChangingEvent;
        }

        public void SampleColumnChangingEvent(object sender, System.Data.DataColumnChangeEventArgs e)
        {
            if (e.Column.ColumnName == OrderDateColumn.ColumnName)
            {
                if ((System.DateTime)e.ProposedValue > System.DateTime.Today)
                {
                    e.Row.SetColumnError("OrderDate", " OrderDate cannot be in the future");
                }
                else
                {
                    e.Row.SetColumnError("OrderDate", "");
                }
            }

        }
    }
}

Press F5.

The data from the Customers and Orders tables appears on the form.

In the DataGridView that contains the orders, change the value in the OrderDate column (of any record) to tomorrow's date.

Navigate off the row to accept the change.

The validation fails and an error icon appears in the OrderDate cell that contains the invalid value.

Rest the mouse pointer on the error icon to see the validation error.

Close the form.