你用的都是vb6的代码,改成:
Private Sub TextBox1_LostFocus(ByVal sender As Object, ByVal e As System.EventArgs) Handles TextBox1.LostFocus
If IsNumeric(TextBox1.Text) = False Then
MsgBox("输入有非数字字符,请重新输入", vbOKOnly, "友情提示")
TextBox1.Focus()
Return
End If
End Sub