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DataGridViewCellToolTipTextNeededEventHandler Delegate

Note: This delegate is new in the .NET Framework version 2.0.

Represents the method that will handle the CellToolTipTextNeeded event of a DataGridView.

Namespace: System.Windows.Forms
Assembly: System.Windows.Forms (in system.windows.forms.dll)

public delegate void DataGridViewCellToolTipTextNeededEventHandler (
	Object sender,
	DataGridViewCellToolTipTextNeededEventArgs e
)
/** @delegate */
public delegate void DataGridViewCellToolTipTextNeededEventHandler (
	Object sender, 
	DataGridViewCellToolTipTextNeededEventArgs e
)
JScript supports the use of delegates, but not the declaration of new ones.

Parameters

sender

The source of the event.

e

A DataGridViewCellToolTipTextNeededEventArgs that contains the event data.

The CellToolTipTextNeeded event occurs only when the DataGridView control DataSource property is set or its VirtualMode property is true.

When you handle the CellToolTipTextNeeded event, the ToolTip text you specify in the handler is shown whenever the mouse pointer is over a cell and the control ShowCellToolTips property value is true. The CellToolTipTextNeeded event is useful when you want to display ToolTips determined by the current state or value of a cell.

The CellToolTipTextNeeded event also occurs whenever the value of the DataGridViewCell.ToolTipText property is retrieved, either programmatically or when the mouse pointer enters a cell.

You can use the DataGridViewCellEventArgs.ColumnIndex and RowIndex properties to determine the state or value of a cell, and use this information to set the ToolTipText property. This property is initialized with the value of the cell ToolTipText property, which the event value overrides.

Handle the CellToolTipTextNeeded event when working with large amounts of data to avoid the performance penalties of setting the cell ToolTipText value for multiple cells. For more information, see Best Practices for Scaling the Windows Forms DataGridView Control.

For more information about handling events, see Consuming Events.

When you create a DataGridViewCellToolTipTextNeededEventHandler delegate, you identify the method that will handle the event. To associate the event with your event handler, add an instance of the delegate to the event. The event handler is called whenever the event occurs, unless you remove the delegate. For more information about event-handler delegates, see Events and Delegates.

The following code example uses ToolTips to display additional information about cell contents in the ReportsTo column.

private DataTable Populate(string query, bool resetUnsharedCounter)
{
    if (resetUnsharedCounter)
    {
        ResetCounter();
    }

    // Alter the data source as necessary
    SqlDataAdapter adapter = new SqlDataAdapter(query,
        new SqlConnection("Integrated Security=SSPI;Persist Security Info=False;" +
        "Initial Catalog=Northwind;Data Source=localhost"));

    DataTable table = new DataTable();
    table.Locale = System.Globalization.CultureInfo.InvariantCulture;
    adapter.Fill(table);
    return table;
}

private Label count = new Label();
private int unsharedRowCounter;

private void ResetCounter()
{
    unsharedRowCounter = 0;
    count.Text = unsharedRowCounter.ToString();
}

private void dataGridView1_CellToolTipTextNeeded(object sender,
    DataGridViewCellToolTipTextNeededEventArgs e)
{

    if (theCellImHoveringOver.ColumnIndex == dataGridView1.Columns["ReportsTo"].Index &&
        theCellImHoveringOver.RowIndex > -1)
    {

        string reportsTo = dataGridView1.Rows[theCellImHoveringOver.RowIndex].
            Cells[theCellImHoveringOver.ColumnIndex].Value.ToString();

        if (String.IsNullOrEmpty(reportsTo))
        {
            e.ToolTipText = "The buck stops here!";
        }
        else
        {
            DataTable table = Populate(
                "select firstname, lastname from employees where employeeid = '" +
                dataGridView1.Rows[theCellImHoveringOver.RowIndex].
                Cells[theCellImHoveringOver.ColumnIndex].Value.ToString() +
                "'", false);

            e.ToolTipText = "Reports to " + table.Rows[0].ItemArray[0] + " " +
                table.Rows[0].ItemArray[1];
        }
    }
}

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, 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.

.NET Framework

Supported in: 2.0

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