Dim currentline As Integer = 0 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        If (RichTextBox1.Lines.Length = 0) Then MsgBox("文本框为空 ")
        Exit Sub
        If (RichTextBox1.Lines.Length <= currentline) Then MsgBox("已到内容尾端 ") : currentline = 0 : Exit Sub
        If Not RichTextBox1.Lines(currentline) = " " Then Clipboard.SetText(RichTextBox1.Lines(currentline))
        currentline += 1
    End Sub