DataGridView.CellValueNeeded DataGridView.CellValueNeeded DataGridView.CellValueNeeded DataGridView.CellValueNeeded Event

定义

在以下情况下发生:当 DataGridView 控件的 VirtualMode 属性为 true,并且 DataGridView 只有在单元格中有值的情况下才格式化和显示单元格时。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;
member this.CellValueNeeded : System.Windows.Forms.DataGridViewCellValueEventHandler 
Public Custom Event CellValueNeeded As DataGridViewCellValueEventHandler 

示例

下面的代码示例处理CellValueNeeded事件以便用正整数填充单元格。The following code example handles the CellValueNeeded event to populate cells with positive integers. 此示例是VirtualMode参考主题中提供的一个更大示例的一部分。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)

注解

使用虚拟模式下的此事件,可使用自定义数据存储区中的数据填充单元,而不会导致行成为非共享行。Use this event in virtual mode to populate cells with data from a custom data store without causing rows to become unshared. 有关行共享的详细信息,请参阅缩放 Windows 窗体 DataGridView 控件的最佳做法For more information about row sharing, see Best Practices for Scaling the Windows Forms DataGridView Control. 有关虚拟模式的详细信息,请参阅Windows 窗体 DataGridView 控件中的虚拟模式For more information about virtual mode, see Virtual Mode in the Windows Forms DataGridView Control.

若要将用户指定的值添加到自定义数据存储, CellValuePushed请处理事件。To add user-specified values to your custom data store, handle the CellValuePushed event.

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.

适用于

另请参阅