How to: Validate Data During Column Changes

Validating data is the process of checking the values being entered into your application's data. Checking these values prior to sending updates to the underlying data store is a good practice that reduces the potential number of round trips between an application and the data store.

You can validate data when the value in a data column changes by responding to the ColumnChanging event. When raised, this event passes an event argument (ProposedValue) that contains the value being proposed for the current column. Based on the contents of e.ProposedValue, you can:

• Accept the proposed value by doing nothing.

• Reject the proposed value by setting the column error (SetColumnError) from within the column-changing event handler.

• Optionally use an ErrorProvider control to display an error message to the user. For more information, see ErrorProvider Component (Windows Forms).

Validation can also be performed during the RowChanging event. For more information, see How to: Validate Data During Row Changes.

To validate data as column values change

1. Open your dataset in the Dataset Designer. For more information, see How to: Open a Dataset in the Dataset Designer.

2. Double-click the column you want to validate. This action creates the ColumnChanging event handler of the DataTable.

   Note

   The Dataset Designer does not automatically create an event handler for the C# event. The code needed to handle the event is included below.

3. Add code to verify that e.ProposedValue contains data that meets the requirements of your application. If the proposed value is unacceptable, then set the column to indicate that it contains an error.

   The following code example sets a column error when the Quantity column is 0 or less. The column-changing event handler should look similar to the following:

   'Visual Basic
   Private Sub Order_DetailsDataTable_ColumnChanging(ByVal sender As System.Object, ByVal e As System.Data.DataColumnChangeEventArgs) _
       Handles Me.ColumnChanging
   
       If (e.Column.ColumnName = Me.QuantityColumn.ColumnName) Then
   
           If CType(e.ProposedValue, Short) <= 0 Then
           e.Row.SetColumnError(e.Column, "Quantity must be greater than 0")
       Else
           e.Row.SetColumnError(e.Column, "")
           End If
       End If
   End Sub
   
   // C#
   // Add this code to the DataTable 
   // partial class.
       public override void EndInit()
       {
           base.EndInit();
           ColumnChanging += SampleColumnChangingEvent;
       }
   
       public void SampleColumnChangingEvent(object sender, System.Data.DataColumnChangeEventArgs e)
       {
           if (e.Column.ColumnName == QuantityColumn.ColumnName)
           {
               if ((short)e.ProposedValue <= 0)
               {
                   e.Row.SetColumnError("Quantity", "Quantity must be greater than 0");
               }
               else
               {
                   e.Row.SetColumnError("Quantity", "");
               }
           }
       }
   

See Also

Tasks

Walkthrough: Displaying Data on a Windows Form

How to: Validate Data in the Windows Forms DataGridView Control

How to: Display Error Icons for Form Validation with the Windows Forms ErrorProvider Component

How to: Connect to Data in a Database

Reference

Data Sources Window

Concepts

TableAdapter Overview

Creating and Editing Typed Datasets

Data Sources Overview

Validating Data