TreeView.ShowPlusMinus Property

Definition

Namespace:

System.Windows.Forms

Assembly:

System.Windows.Forms.dll

Source:

TreeView.cs

Gets or sets a value indicating whether plus-sign (+) and minus-sign (-) buttons are displayed next to tree nodes that contain child tree nodes.

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

Property Value

Boolean

true if plus sign and minus sign buttons are displayed next to tree nodes that contain child tree nodes; otherwise, false. The default is true.

Examples

The following code example illustrates a customized TreeView. By inheriting the TreeView class, this custom version has all the functionality of a typical TreeView. Changing various property values in the constructor provides a unique appearance. Because the ShowPlusMinus property is set to false, the customized control also overrides the OnAfterSelect method so that nodes can be expanded and collapsed when they are clicked.

A control that is customized in this way can be used throughout an organization, making it easy to provide a consistent interface without requiring the control properties to be specified in each individual project.

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

Remarks

The plus sign and minus sign buttons appear next to the root tree nodes only if the ShowRootLines property value is true. If the plus sign and minus sign buttons are not displayed, no visual cue exists to indicate that the tree node contains child tree nodes and is expandable. The user then must double-click a tree node to determine whether it contains child tree nodes, to expand it, or to collapse it.

See also

• ShowRootLines