Gets the number of segments in the tree.
            
 Declaration Syntax
 Declaration SyntaxAssembly: ICSharpCode.AvalonEdit (Module: ICSharpCode.AvalonEdit.dll) Version: 5.0.0.4238
 Declaration Syntax
 Declaration SyntaxAssembly: ICSharpCode.AvalonEdit (Module: ICSharpCode.AvalonEdit.dll) Version: 5.0.0.4238