// Begin the update operation treeView1.BeginUpdate(); // Add nodes to the tree view TreeNode node1 = new TreeNode("Node 1"); treeView1.Nodes.Add(node1); // End the update operation treeView1.EndUpdate();In this example, the BeginUpdate method is called before adding nodes to the TreeView control, and the EndUpdate method is called after all the nodes have been added. This avoids updating the control for each node added, resulting in faster performance. The System.Windows.Forms TreeView BeginUpdate method is part of the .NET Framework Class Library, which is included in the System.Windows.Forms namespace.