The zero-based index of the first occurrence of a tree node with the specified key, if found; otherwise, -1.
If TreeNodeCollection.IndexOfKey(string) is called successively, the last returned index will be checked for a key match first, and if there is no match, the search starts at the beginning of the collection.
The TreeNode.Name property corresponds to the key for a System.Windows.Forms.TreeNode in the System.Windows.Forms.TreeNodeCollection.
The key comparison is not case-sensitive. If key is null or an empty string, the TreeNodeCollection.Item(string) property returns -1.