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NewRowNeeded Event
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DataGridView.NewRowNeeded Event

Occurs when the VirtualMode property of the DataGridView is true and the user navigates to the new row at the bottom of the DataGridView.

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

public event DataGridViewRowEventHandler NewRowNeeded

When the DataGridView is in virtual mode, this event allows a new entry to be created in the data store for the new row, and it also allows for the row to be populated with default values.

For more information about handling events, see Consuming Events.

The following code example uses the NewRowNeeded event to track when a new row is being added, so logic in the CellValueNeeded event handler can initialize a new row's cell to an initial value. This example is part of a larger example available in the VirtualMode reference topic.

bool newRowNeeded;
private void dataGridView1_NewRowNeeded(object sender,
    DataGridViewRowEventArgs e)
{
    newRowNeeded = true;
}

const int initialSize = 5000000;
int numberOfRows = initialSize;

private void dataGridView1_RowsAdded(object sender,
     DataGridViewRowsAddedEventArgs e)
{
    if (newRowNeeded)
    {
        newRowNeeded = false;
        numberOfRows = numberOfRows + 1;
    }
}

#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>();

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.

.NET Framework

Supported in: 3.5, 3.0, 2.0

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