DataGridView.CellValueNeeded Event
Assembly: System.Windows.Forms (in system.windows.forms.dll)
'Declaration Public Event CellValueNeeded As DataGridViewCellValueEventHandler 'Usage Dim instance As DataGridView Dim handler As DataGridViewCellValueEventHandler AddHandler instance.CellValueNeeded, handler
/** @event */ public void add_CellValueNeeded (DataGridViewCellValueEventHandler value) /** @event */ public void remove_CellValueNeeded (DataGridViewCellValueEventHandler value)
JScript supports the use of events, but not the declaration of new ones.
Use this event in virtual mode to populate cells with data from a custom data store without causing rows to become unshared. For more information about row sharing, see Best Practices for Scaling the Windows Forms DataGridView Control. For more information about virtual mode, see Virtual Mode in the Windows Forms DataGridView Control.
To add user-specified values to your custom data store, handle the CellValuePushed event.
For more information about handling events, see Consuming Events.
The following code example handles the CellValueNeeded event to populate cells with positive integers. This example is part of a larger example available in the VirtualMode reference topic.
#Region "data store maintance" Const initialValue As Integer = -1 Private Sub dataGridView1_CellValueNeeded(ByVal sender As Object, _ ByVal e As DataGridViewCellValueEventArgs) _ Handles dataGridView1.CellValueNeeded If store.ContainsKey(e.RowIndex) Then ' Use the store if the e value has been modified ' and stored. e.Value = store(e.RowIndex) ElseIf newRowNeeded AndAlso e.RowIndex = numberOfRows Then If dataGridView1.IsCurrentCellInEditMode Then e.Value = initialValue Else ' Show a blank value if the cursor is just resting ' on the last row. e.Value = String.Empty End If Else e.Value = e.RowIndex End If End Sub Private Sub dataGridView1_CellValuePushed(ByVal sender As Object, _ ByVal e As DataGridViewCellValueEventArgs) _ Handles dataGridView1.CellValuePushed store.Add(e.RowIndex, CInt(e.Value)) End Sub #End Region Dim store As System.Collections.Generic.Dictionary(Of Integer, Integer) = _ New Dictionary(Of Integer, Integer)
#region "data store maintance"
private final int INITIALVALUE = -1;
private void dataGridView1_CellValueNeeded(Object sender,
DataGridViewCellValueEventArgs e)
{
if (store.ContainsKey(e.get_RowIndex())) {
// Use the store if the e value has been modified
// and stored.
e.set_Value((Int32)store.get_Item(e.get_RowIndex()));
}
else {
if (newRowNeeded && e.get_RowIndex() == numberOfRows) {
if (dataGridView1.get_IsCurrentCellInEditMode()) {
e.set_Value((Int32)INITIALVALUE);
}
else {
// Show a blank e if the cursor is just loitering
// over(the)
// last row.
e.set_Value("");
}
}
else {
e.set_Value((Int32)e.get_RowIndex());
}
}
} //dataGridView1_CellValueNeeded
private void dataGridView1_CellValuePushed(Object sender,
DataGridViewCellValueEventArgs e)
{
store.Add(e.get_RowIndex(), Int32.Parse(e.get_Value().ToString()));
} //dataGridView1_CellValuePushed
#endregion
private Dictionary<int, int> store = new Dictionary<int, int>();
Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.
Reference
DataGridView ClassDataGridView Members
System.Windows.Forms Namespace
DataGridView.VirtualMode Property
DataGridViewCellValueEventHandler
DataGridViewCellValueEventArgs
CellValuePushed
OnCellValueNeeded
Other Resources
Best Practices for Scaling the Windows Forms DataGridView ControlVirtual Mode in the Windows Forms DataGridView Control
DataGridView Control (Windows Forms)