Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
The RowErrorTextNeeded event occurs only when the DataGridView control DataSource property is set or its VirtualMode property is true. Handling the RowErrorTextNeeded event is useful when you want to determine the error for a row depending on its state and the values it contains.
When you handle the RowErrorTextNeeded event and specify error text in the handler, an error glyph appears in the row header unless the DataGridView::ShowRowErrors property is set to false. When the user moves the mouse pointer over the error glyph, the error text appears in a ToolTip.
You can use the RowIndex property to determine the state or value of a row, and use this information to change or modify the ErrorText property. This property is initialized with the value of the row ErrorText property, which the event value overrides.
Handle the RowErrorTextNeeded event when working with large amounts of data to avoid the performance penalties of setting the row ErrorText value for multiple rows. For more information, see Best Practices for Scaling the Windows Forms DataGridView Control.
For more information about handling events, see Consuming Events.
The following code example demonstrates the use of this type. In the example, an event handler reports on the occurrence of the RowErrorTextNeeded event. This report helps you to learn when the event occurs and can assist you in debugging. To report on multiple events or on events that occur frequently, consider replacing Show with Console::WriteLine or appending the message to a multiline TextBox.
To run the example code, paste it into a project that contains an instance of type DataGridView named DataGridView1. Then ensure that the event handler is associated with the RowErrorTextNeeded event.
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.