TreeViewEventArgs Class
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TreeViewEventArgs Class


Provides data for the AfterCheck, AfterCollapse, AfterExpand, or AfterSelect events of a TreeView control.

Namespace:   System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)


public class TreeViewEventArgs : EventArgs


Initializes a new instance of the TreeViewEventArgs class for the specified tree node.

System_CAPS_pubmethodTreeViewEventArgs(TreeNode, TreeViewAction)

Initializes a new instance of the TreeViewEventArgs class for the specified tree node and with the specified type of action that raised the event.


Gets the type of action that raised the event.


Gets the tree node that has been checked, expanded, collapsed, or selected.


Determines whether the specified object is equal to the current object.(Inherited from Object.)


Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)


Serves as the default hash function. (Inherited from Object.)


Gets the Type of the current instance.(Inherited from Object.)


Creates a shallow copy of the current Object.(Inherited from Object.)


Returns a string that represents the current object.(Inherited from Object.)

For more information about handling events, see Handling and Raising Events.

The following example illustrates a customized TreeView. By inheriting the TreeView class, this custom version has all the functionality of a normal 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 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 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) 

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


.NET Framework
Available since 1.1

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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