TreeNode.Expanded Property
Assembly: System.Web (in system.web.dll)
public: property Nullable<bool> Expanded { Nullable<bool> get (); void set (Nullable<bool> value); }
/** @property */ public Nullable<boolean> get_Expanded () /** @property */ public void set_Expanded (Nullable<boolean> value)
public function get Expanded () : Nullable<boolean> public function set Expanded (value : Nullable<boolean>)
Not applicable.
Property Value
true if the node is expanded, false if the node is not expanded, or a null reference (Nothing in Visual Basic).Use the Expanded property to specify or determine whether the node is expanded.
You can expand and collapse a node by calling the Expand and Collapse methods, respectively. You can also expand and collapse a node and all its child nodes by calling the ExpandAll and CollapseAll methods, respectively.
Since the Expanded property is a tri-state property, the following C# code snippet causes a compile error:
protected void TreeView1_SelectedNodeChanged(object sender, EventArgs e)
{
if (TreeView1.Nodes[0].Expanded)
{
// some work here
}
}
While VB.Net implicitly casts the Boolean value to a NullableBoolean, C# does not. Therefore, it is a best practice to explicitly check the state of the property. For example, the following code examples in Visual Basic and C# explicitly test the value of the Expanded property.
The following Visual Basic code example explicitly tests the value of the Expanded property. This example tests if the Expanded property is set to True; therefore Nothing and False fall through the If statement.
If TreeView1.Nodes(0).Expanded = True Then 'some work hereEnd IF
This C# code example explicitly tests the value of the Expanded property. This example tests if the Expanded property is set to True; therefore Null and False fall through the If statement.
if( TreeView1.Nodes[0].Expanded == true ) { //some work here}
| Topic | Location |
|---|---|
| How to: Add or Delete TreeView Node Elements (Visual Studio) | Building ASP .NET Web Applications in Visual Studio |
The following code example demonstrates how to use the Expanded property to programmatically expand a node. It initializes all nodes with a depth of one to an expanded state. Notice that when the root node is expanded, its child nodes are already expanded. For this example to work correctly, you must copy the sample XML data below to a file named Book.xml.
The following code is sample XML data for the previous example.
<Book Title="Book Title">
<Chapter Heading="Chapter 1">
<Section Heading="Section 1">
</Section>
<Section Heading="Section 2">
</Section>
</Chapter>
<Chapter Heading="Chapter 2">
<Section Heading="Section 1">
</Section>
</Chapter>
</Book>