[VB.NET]用Extension Method取得CustomAttributes

Module EnumExtension

<Extension()> _
Function GetCustomAttributes(Of T)(ByVal e As [Enum]) As IEnumerable(Of T)
    Return e.GetType.GetField(e.ToString).GetCustomAttributes(GetType(T), False).Cast(Of T)()
End Function

<Extension()> _
Function GetCustomAttribute(Of T)(ByVal e As [Enum]) As T
    Return GetCustomAttributes(Of T)(e).FirstOrDefault
End Function

End Module

Module TypeExtension

<Extension()> _
Function GetCustomAttributes(Of T)(ByVal type As Type) As IEnumerable(Of T)
    Return type.GetCustomAttributes(GetType(T), False).Cast(Of T)()
End Function

<Extension()> _
Function GetCustomAttribute(Of T)(ByVal type As Type) As T
    Return DirectCast(GetCustomAttributes(Of T)(type).FirstOrDefault, T)
End Function

<Extension()> _
Function GetCustomAttributes(Of T)(ByVal type As Type, ByVal memberName As String) As IEnumerable(Of T)
    Dim m = type.GetMember(memberName).FirstOrDefault
    If m Is Nothing Then
        Throw New MissingMemberException
    End If
    Return m.GetCustomAttributes(GetType(T), False)
End Function

<Extension()> _
Function GetCustomAttribute(Of T)(ByVal type As Type, ByVal memberName As String) As T
    Return GetCustomAttributes(Of T)(type, memberName).FirstOrDefault
End Function

End Module

Module ObjectExtension

<Extension()> _
Function GetCustomAttributes(Of T)(ByVal obj As Object) As IEnumerable(Of T)
    Return obj.GetType.GetCustomAttributes(GetType(T), False).Cast(Of T)()
End Function

<Extension()> _
Function GetCustomAttribute(Of T)(ByVal obj As Object) As T
    Return GetCustomAttributes(Of T)(obj).FirstOrDefault
End Function

<Extension()> _
Function GetCustomAttributes(Of T)(ByVal obj As Object, ByVal memberName As String) As IEnumerable(Of T)
    Dim m = obj.GetType.GetMember(memberName).FirstOrDefault
    If m Is Nothing Then
        Throw New MissingMemberException
    End If
    Return m.GetCustomAttributes(GetType(T), False)
End Function

<Extension()> _
Function GetCustomAttribute(Of T)(ByVal obj As Object, ByVal memberName As String) As T
    Return GetCustomAttributes(Of T)(obj, memberName).FirstOrDefault
End Function

End Module

Enum InterfaceType
    <Description("RS232 Interface")> _
    RS232

    <Description("RS485 Interface")> _
    RS485

    <Description("GPIB Interface")> _
    GPIB

    <Description("I2C Interface")> _
    I2C
End Enum

<Description("Test Class")> _
Class TestClass

    <Description("Test Property")> _
    Property TestProperty As String

End Class

Sub Main()
    Dim c As New TestClass
    Console.WriteLine(InterfaceType.GPIB.GetCustomAttribute(Of DescriptionAttribute)().Description)
    Console.WriteLine(c.GetCustomAttribute(Of DescriptionAttribute).Description)
    Console.WriteLine(c.GetCustomAttribute(Of DescriptionAttribute)("TestProperty").Description)
End Sub

End Module

• VB.NET