看看下面的代码，怎么没有错误提示呀！！！！！！ 自己建的类： Private name As String Public Property nm() As String Get Return Me.name End Get Set(ByVal value As String) Try If value <= 10 And value > = 1 Then Me.name = value End If Catch ex As Exception MessageBox.Show(ex.Message) End Try End Set End Property 按钮为4： Private Sub Button4_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button4.Click Dim nam As New Class1 nam.nm = 1333 MessageBox.Show(nam.nm) End Sub __________________________________________________________________________ Public Class Class1 Private name As String Public Property nm() As String Get Return Me.name End Get Set(ByVal value As String) Try If value <= 10 And value > = 1 Then Me.name = value Else Me.name = "Error " Throw New Exception( "The value is out of range. ") End If Catch ex As Exception MessageBox.Show(ex.Message) End Try End Set End Property End Class __________________________________________________________________________ Set(ByVal value As String) Try If value <= 10 And value > = 1 Then 到底是string还是int类型？ 如果是string要用 len()求哦。 __________________________________________________________________________ 楼主错误理解了Try的使用方法，如果没有出系统级别错误Try是不会报错的 应将如下代码进行修改： Try If value <= 10 And value > = 1 Then Me.name = value End If Catch ex As Exception MessageBox.Show(ex.Message) End Try 改后代码： If value <= 10 And value > = 1 Then Me.name = value Else MsgBox(Value) End If __________________________________________________________________________ VB.NET默认允许隐式转换 value 会自动转换为Double类型 楼主是不是希望检测字符串长度，不太明白，给出两种方式，尽量不要用Try做逻辑验证 If value Is Nothing Then MsgBox( "传入的值为空！ ") : Exit Property If value.Length > 0 AndAlso value.Length < 11 Then Me.name = value Else MsgBox( "传入的值溢出！ ") End If If IsNumeric(value) = True Then If CInt(value) > 0 AndAlso CInt(value) < 11 Then Me.name = value Else MsgBox( "传入的值溢出！ ") End If Else MsgBox( "传入的值不是数字类型！ ") End If __________________________________________________________________________ 好像是问题问的有点不太清楚，在这里补充一下！！！ 进行错误提示，但是当我将nam.nm = 1333时，系统却没有提示我出错 我规定的范围时 从 1 到 10 超出范围了但是没有提示我出错，这怎么解决呀！！！！！ __________________________________________________________________________ 超出了范围如果想明确的引发自定义的异常，必须自己Throw出来一个异常 就像楼上各位举的例子一样.. __________________________________________________________________________ 那用 try 里的 messageBox.show(ex.message) 不行吗？？？ 还是只能用throw 呀！！！！！ __________________________________________________________________________ 是不是这样最简单： Try If cint(value) <= 10 And cint(value) > = 1 Then Me.name = value End If Catch ex As Exception Throw New Exception(ex.Message) End Try __________________________________________________________________________ 这样也不会抛出错误吧？ __________________________________________________________________________ Private name As String Public Property nm() As String Get Return Me.name End Get Set(ByVal value As String) If value <= 10 And value > = 1 Then Me.name = value Else ‘抛出自定义的异常咯... End If End Set End Property __________________________________________________________________________ Public Property nm() As String Get Return Me.name End Get Set(ByVal value As String) If CInt(val(value)) <= 10 And CInt(val(value)) > = 1 Then Me.name = value Else ‘抛出自定义的异常咯... End If End Set End Property __________________________________________________________________________ 根本没有发生异常,怎么又会报错呢 __________________________________________________________________________ 当你代码出现异常时才会报错！ __________________________________________________________________________ Private name As String Public Property nm() As String Get Return Me.name End Get Set(ByVal value As String) Try If value <= 10 And value > = 1 Then Me.name = value else Catch ex As Exception MessageBox.Show(ex.Message) EndIf End Try End Set End Property __________________________________________________________________________