DataGridView.CellValueNeeded Event
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Occurs when the VirtualMode property of the DataGridView control is true
and the DataGridView requires a value for a cell in order to format and display the cell.
public:
event System::Windows::Forms::DataGridViewCellValueEventHandler ^ CellValueNeeded;
public event System.Windows.Forms.DataGridViewCellValueEventHandler CellValueNeeded;
public event System.Windows.Forms.DataGridViewCellValueEventHandler? CellValueNeeded;
member this.CellValueNeeded : System.Windows.Forms.DataGridViewCellValueEventHandler
Public Custom Event CellValueNeeded As DataGridViewCellValueEventHandler
Event Type
Examples
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.
#pragma region Data store maintance
void VirtualConnector::dataGridView1_CellValueNeeded
(Object^ sender, DataGridViewCellValueEventArgs^ e)
{
if (store->ContainsKey(e->RowIndex))
{
// Use the store if the e value has been modified
// and stored.
e->Value = gcnew Int32(store->default[e->RowIndex]);
}
else if (newRowNeeded && e->RowIndex == numberOfRows)
{
if (dataGridView1->IsCurrentCellInEditMode)
{
e->Value = initialValue;
}
else
{
// Show a blank e if the cursor is just loitering
// over(the) last row.
e->Value = String::Empty;
}
}
else
{
e->Value = e->RowIndex;
}
}
void VirtualConnector::dataGridView1_CellValuePushed
(Object^ sender, DataGridViewCellValueEventArgs^ e)
{
String^ value = e->Value->ToString();
store[e->RowIndex] = Int32::Parse(value,
CultureInfo::CurrentCulture);
}
#pragma endregion
#region "data store maintance"
const int initialValue = -1;
private void dataGridView1_CellValueNeeded(object sender,
DataGridViewCellValueEventArgs e)
{
if (store.ContainsKey(e.RowIndex))
{
// Use the store if the e value has been modified
// and stored.
e.Value = store[e.RowIndex];
}
else if (newRowNeeded && e.RowIndex == numberOfRows)
{
if (dataGridView1.IsCurrentCellInEditMode)
{
e.Value = initialValue;
}
else
{
// Show a blank value if the cursor is just resting
// on the last row.
e.Value = String.Empty;
}
}
else
{
e.Value = e.RowIndex;
}
}
private void dataGridView1_CellValuePushed(object sender,
DataGridViewCellValueEventArgs e)
{
store.Add(e.RowIndex, int.Parse(e.Value.ToString()));
}
#endregion
private Dictionary<int, int> store = new Dictionary<int, int>();
#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)
Remarks
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 how to handle events, see Handling and Raising Events.
Applies to
See also
- VirtualMode
- DataGridViewCellValueEventHandler
- DataGridViewCellValueEventArgs
- CellValuePushed
- OnCellValueNeeded(DataGridViewCellValueEventArgs)
- Best Practices for Scaling the Windows Forms DataGridView Control
- Virtual Mode in the Windows Forms DataGridView Control
- DataGridView Control (Windows Forms)