TreeView.ShowPlusMinus 属性

定义

命名空间:

System.Windows.Forms

程序集:

System.Windows.Forms.dll

获取或设置一个值，用以指示是否在包含子树节点的树节点旁显示加号 (+) 和减号 (-) 按钮。

public:
 property bool ShowPlusMinus { bool get(); void set(bool value); };

public bool ShowPlusMinus { get; set; }

member this.ShowPlusMinus : bool with get, set

Public Property ShowPlusMinus As Boolean

属性值

Boolean

如果在包含子树节点的树节点旁显示加号和减号按钮，则为 true；否则为 false。 默认值为 true。

示例

下面的代码示例演示了自定义 TreeView的 。 通过继承 TreeView 类，此自定义版本具有典型 TreeView的所有功能。 更改构造函数中的各种属性值可提供独特的外观。 由于属性 ShowPlusMinus 设置为 false，因此自定义控件还会重写 OnAfterSelect 该方法，以便在单击节点时可以展开和折叠节点。

可以通过这种方式自定义的控件在整个组织中使用，因此可以轻松提供一致的界面，而无需在每个单独的项目中指定控件属性。

public ref class CustomizedTreeView: public TreeView
{
public:
   CustomizedTreeView()
   {

      // Customize the TreeView control by setting various properties.
      BackColor = System::Drawing::Color::CadetBlue;
      FullRowSelect = true;
      HotTracking = true;
      Indent = 34;
      ShowPlusMinus = false;

      // The ShowLines property must be false for the FullRowSelect
      // property to work.
      ShowLines = false;
   }

protected:
   virtual void OnAfterSelect( TreeViewEventArgs^ e ) override
   {
      // Confirm that the user initiated the selection.
      // This prevents the first node from expanding when it is
      // automatically selected during the initialization of
      // the TreeView control.
      if ( e->Action != TreeViewAction::Unknown )
      {
         if ( e->Node->IsExpanded )
         {
            e->Node->Collapse();
         }
         else
         {
            e->Node->Expand();
         }
      }

      
      // Remove the selection. This allows the same node to be
      // clicked twice in succession to toggle the expansion state.
      SelectedNode = nullptr;
   }
};

public class CustomizedTreeView : TreeView
{
    public CustomizedTreeView()
    {
        // Customize the TreeView control by setting various properties.
        BackColor = System.Drawing.Color.CadetBlue;
        FullRowSelect = true;
        HotTracking = true;
        Indent = 34;
        ShowPlusMinus = false;

        // The ShowLines property must be false for the FullRowSelect 
        // property to work.
        ShowLines = false;
    }

    protected override void OnAfterSelect(TreeViewEventArgs e)
    {
        // Confirm that the user initiated the selection.
        // This prevents the first node from expanding when it is
        // automatically selected during the initialization of 
        // the TreeView control.
        if (e.Action != TreeViewAction.Unknown)
        {
            if (e.Node.IsExpanded) 
            {
                e.Node.Collapse();
            }
            else 
            {
                e.Node.Expand();
            }
        }

        // Remove the selection. This allows the same node to be
        // clicked twice in succession to toggle the expansion state.
        SelectedNode = null;
    }
}

Public Class CustomizedTreeView
    Inherits TreeView

    Public Sub New()
        ' Customize the TreeView control by setting various properties.
        BackColor = System.Drawing.Color.CadetBlue
        FullRowSelect = True
        HotTracking = True
        Indent = 34
        ShowPlusMinus = False

        ' The ShowLines property must be false for the FullRowSelect 
        ' property to work.
        ShowLines = False
    End Sub


    Protected Overrides Sub OnAfterSelect(ByVal e As TreeViewEventArgs)
        ' Confirm that the user initiated the selection.
        ' This prevents the first node from expanding when it is
        ' automatically selected during the initialization of 
        ' the TreeView control.
        If e.Action <> TreeViewAction.Unknown Then
            If e.Node.IsExpanded Then
                e.Node.Collapse()
            Else
                e.Node.Expand()
            End If
        End If

        ' Remove the selection. This allows the same node to be
        ' clicked twice in succession to toggle the expansion state.
        SelectedNode = Nothing
    End Sub

End Class

注解

仅当属性值为 true 时ShowRootLines，根树节点旁边才会显示加号和减号按钮。 如果未显示加号和减号按钮，则不存在视觉提示以指示树节点包含子树节点且可展开。 然后，用户必须双击树节点以确定它是否包含子树节点、展开它或折叠它。

另请参阅

• ShowRootLines