Expand Minimize

DataGridView.CellValueNeeded Event

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.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

public event DataGridViewCellValueEventHandler CellValueNeeded

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 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>();

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
Was this page helpful?
(1500 characters remaining)
Thank you for your feedback
Show:
© 2015 Microsoft