DataGridViewCellToolTipTextNeededEventHandler 委托


表示将用来处理 CellToolTipTextNeededDataGridView 事件的方法。Represents the method that will handle the CellToolTipTextNeeded event of a DataGridView.

public delegate void DataGridViewCellToolTipTextNeededEventHandler(System::Object ^ sender, DataGridViewCellToolTipTextNeededEventArgs ^ e);
public delegate void DataGridViewCellToolTipTextNeededEventHandler(object sender, DataGridViewCellToolTipTextNeededEventArgs e);
type DataGridViewCellToolTipTextNeededEventHandler = delegate of obj * DataGridViewCellToolTipTextNeededEventArgs -> unit
Public Delegate Sub DataGridViewCellToolTipTextNeededEventHandler(sender As Object, e As DataGridViewCellToolTipTextNeededEventArgs)



事件源。The source of the event.



下面的代码示例使用工具提示显示有关列中的单元格内容ReportsTo的其他信息。The following code example uses ToolTips to display additional information about cell contents in the ReportsTo column.

DataTable^ Populate( String^ query, bool resetUnsharedCounter )
    if ( resetUnsharedCounter )

    // Alter the data source as necessary
    SqlDataAdapter^ adapter = gcnew SqlDataAdapter( query,
        gcnew SqlConnection( L"Integrated Security=SSPI;Persist Security Info=False;"
        L"Initial Catalog=Northwind;Data Source= localhost" ) );
    DataTable^ table = gcnew DataTable;
    adapter->Fill( table );
    return table;

Label^ count;
int unsharedRowCounter;
void ResetCounter()
    unsharedRowCounter = 0;
    count->Text = unsharedRowCounter.ToString();

void dataGridView1_CellToolTipTextNeeded( Object^ /*sender*/,
    DataGridViewCellToolTipTextNeededEventArgs^ e )
    if ( theCellImHoveringOver->ColumnIndex == dataGridView1->Columns[ L"ReportsTo" ]->Index && theCellImHoveringOver->RowIndex > -1 )
        String^ reportsTo = dataGridView1->Rows[ theCellImHoveringOver->RowIndex ]->Cells[ theCellImHoveringOver->ColumnIndex ]->Value->ToString();
        if ( reportsTo->Equals( L"" ) )
            e->ToolTipText = L"The buck stops here!";
            DataTable^ table = Populate( String::Format( L"select firstname, lastname from employees where employeeid = '{0}'",
                dataGridView1->Rows[ theCellImHoveringOver->RowIndex ]->Cells[ theCellImHoveringOver->ColumnIndex ]->Value ), false );
            e->ToolTipText = String::Format( L"Reports to {0} {1}", table->Rows[ 0 ]->ItemArray[ 0 ], table->Rows[ 0 ]->ItemArray[ 1 ] );

private DataTable Populate(string query, bool resetUnsharedCounter)
    if (resetUnsharedCounter)

    // 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;
    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].

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

            e.ToolTipText = "Reports to " + table.Rows[0].ItemArray[0] + " " +
Private Function Populate(ByVal query As String, ByVal resetUnsharedCounter As Boolean) As DataTable

    If resetUnsharedCounter Then
    End If

    ' Alter the data source as necessary
    Dim adapter As New SqlDataAdapter(query, _
        New SqlConnection("Integrated Security=SSPI;Persist Security Info=False;" & _
        "Initial Catalog=Northwind;Data Source=localhost"))

    Dim table As New DataTable()
    table.Locale = System.Globalization.CultureInfo.InvariantCulture
    Return table
End Function

Private count As New Label()
Private unsharedRowCounter As Integer

Private Sub ResetCounter()
    unsharedRowCounter = 0
    count.Text = unsharedRowCounter.ToString()
End Sub

Private Sub DataGridView1_CellToolTipTextNeeded(ByVal sender As Object, _
    ByVal e As DataGridViewCellToolTipTextNeededEventArgs) _
    Handles dataGridView1.CellToolTipTextNeeded

    If theCellImHoveringOver.ColumnIndex = dataGridView1.Columns("ReportsTo").Index AndAlso _
            theCellImHoveringOver.RowIndex > -1 Then

        Dim reportsTo As String = dataGridView1.Rows(theCellImHoveringOver.RowIndex). _
        If String.IsNullOrEmpty(reportsTo) Then
            e.ToolTipText = "The buck stops here!"
            Dim table As DataTable = 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).Item(0).ToString() & " " & table.Rows(0).Item(1).ToString()
        End If
    End If
End Sub


CellToolTipTextNeeded VirtualMode true当控件属性DataSource已设置或其属性为时, 才会发生此事件。 DataGridViewThe CellToolTipTextNeeded event occurs only when the DataGridView control DataSource property is set or its VirtualMode property is true.

处理CellToolTipTextNeeded事件时, 每当鼠标指针位于单元格上并且控件ShowCellToolTips属性值为true时, 就会显示在处理程序中指定的工具提示文本。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. 若要显示由当前状态或单元值决定的工具提示,事件会很有用。CellToolTipTextNeededThe CellToolTipTextNeeded event is useful when you want to display ToolTips determined by the current state or value of a cell.

CellToolTipTextNeeded以编程方式或鼠标指针进入单元DataGridViewCell.ToolTipText格的情况下检索属性值时, 也会发生此事件。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.

您可以使用DataGridViewCellEventArgs.ColumnIndexRowIndex属性来确定单元的状态或值, 并使用ToolTipText此信息来设置属性。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. 此属性将用单元ToolTipText属性的值进行初始化, 该属性的值将重写。This property is initialized with the value of the cell ToolTipText property, which the event value overrides.

处理大量数据时处理ToolTipText 事件,以避免为多个单元格设置单元值时的性能损失。CellToolTipTextNeededHandle the CellToolTipTextNeeded event when working with large amounts of data to avoid the performance penalties of setting the cell ToolTipText value for multiple cells. 有关详细信息,请参阅 缩放 Windows 窗体 DataGridView 控件的最佳做法For more information, see Best Practices for Scaling the Windows Forms DataGridView Control.

有关如何处理事件的详细信息, 请参阅处理和引发事件For more information about how to handle events, see Handling and Raising Events.

创建 DataGridViewCellToolTipTextNeededEventHandler 委托时,需要标识将处理该事件的方法。When you create a DataGridViewCellToolTipTextNeededEventHandler delegate, you identify the method that will handle the event. 若要将事件与事件处理程序关联,请将该委托的一个实例添加到事件中。To associate the event with your event handler, add an instance of the delegate to the event. 除非移除了该委托,否则每当发生该事件时就会调用事件处理程序。The event handler is called whenever the event occurs, unless you remove the delegate. 有关事件处理程序委托的详细信息, 请参阅处理和引发事件For more information about event-handler delegates, see Handling and Raising Events.



获取指示指定委托表示的方法的对象。Gets an object that represents the method represented by the specified delegate.