[程序设计]程序菜鸟求救，s=String(Tlong,chr(0)) 运行时为什么显示“string是一个类

Private Declare Function GetWindowTextLength Lib "user32" Alias "GetWindowTextLengthA" (ByVal hwnd As Long) As Long
　　Private Declare Function GetWindowText Lib "user32" Alias "GetWindowTextA" (ByVal hwnd As Long, ByVal lpString As String, ByVal cch As Long) As Long
　　运行环境，VB.NET 2005
　　Private Sub Command1_Click()
　　Dim Tlong as long,s as String
　　Tlong=GetWindowTextLength(hwnd)+1
　　s=String$(Tlong,chr(0)) '必须要的
　　GetWindowText hwnd,s,Tlong
　　Msgbox s
　　End Sub
　　hwnd是你获得的窗体句柄，s就是你要的窗体标题了