operators.vb

大名鼎鼎的mono是.NET平台的跨平台（支持linux

            Return CType(s, SByte)
        End Function

        Private Shared Function AddSingles(ByVal o1 As Single, ByVal o2 As Single) As Object
            Return o1 + o2
        End Function

        Private Shared Function AddStrings(ByVal o1 As String, ByVal o2 As String) As Object
            Return o1 + o2
        End Function

        Private Shared Function AddUInt16s(ByVal o1 As UShort, ByVal o2 As UShort) As Object
            Dim int As Integer = CType(o1, Integer) + o2
            If (int > UShort.MaxValue) Then
                Return int
            End If
            Return CType(int, UShort)
        End Function

        Private Shared Function AddUInt32s(ByVal o1 As UInteger, ByVal o2 As UInteger) As Object
            Dim l As Long = CType(o1, Long) + o2
            If (l > UInteger.MaxValue) Then
                Return l
            End If
            Return CType(l, UInteger)
        End Function

        Private Shared Function AddUInt64s(ByVal o1 As ULong, ByVal o2 As ULong) As Object
            Return o1 + o2
        End Function

        Public Shared Function AddObject(ByVal o1 As Object, ByVal o2 As Object) As Object
            If (o1 Is Nothing) And (o2 Is Nothing) Then
                Return 0
            End If
            If (o1 Is Nothing) Then
                o1 = CreateNullObjectType(o2)
            End If
            If (o2 Is Nothing) Then
                o2 = CreateNullObjectType(o1)
            End If

            Dim destTc As TypeCode = DestTypeCodeOpAdd(o1, o2)
            Try
                Select Case destTc
                    'Case TypeCode.Empty -> break
                    Case TypeCode.Boolean
                        Return AddBooleans(VBConvert.ToBoolean(o1), VBConvert.ToBoolean(o2))
                    Case TypeCode.Byte
                        Return AddBytes(VBConvert.ToByte(o1), VBConvert.ToByte(o2))
                    Case TypeCode.Char
                        Return AddChars(VBConvert.ToChar(o1), VBConvert.ToChar(o2))
                    Case TypeCode.DateTime
                        Return AddDateTimes(VBConvert.ToDateTime(o1), VBConvert.ToDateTime(o2))
                    Case TypeCode.Decimal
                        Return AddDecimals(VBConvert.ToDecimal(o1), VBConvert.ToDecimal(o2))
                    Case TypeCode.Double
                        Return AddDoubles(VBConvert.ToDouble(o1), VBConvert.ToDouble(o2))
                    Case TypeCode.Int16
                        Return AddInt16s(VBConvert.ToInt16(o1), VBConvert.ToInt16(o2))
                    Case TypeCode.Int32
                        Return AddInt32s(VBConvert.ToInt32(o1), VBConvert.ToInt32(o2))
                    Case TypeCode.Int64
                        Return AddInt64s(VBConvert.ToInt64(o1), VBConvert.ToInt64(o2))
                    Case TypeCode.SByte
                        Return AddSBytes(VBConvert.ToSByte(o1), VBConvert.ToSByte(o2))
                    Case TypeCode.Single
                        Return AddSingles(VBConvert.ToSingle(o1), VBConvert.ToSingle(o2))
                    Case TypeCode.String
                        Return AddStrings(VBConvert.ToString(o1), VBConvert.ToString(o2))
                    Case TypeCode.UInt16
                        Return AddUInt16s(VBConvert.ToUInt16(o1), VBConvert.ToUInt16(o2))
                    Case TypeCode.UInt32
                        Return AddUInt32s(VBConvert.ToUInt32(o1), VBConvert.ToUInt32(o2))
                    Case TypeCode.UInt64
                        Return AddUInt64s(VBConvert.ToUInt64(o1), VBConvert.ToUInt64(o2))

                End Select
                Return AddObjects(o1, o2)
            Catch ex As Exception
            End Try
            Throw New InvalidCastException("Operator '+' is not defined for type '" + GetTypeCode(o1).ToString() + "' and type '" + GetTypeCode(o2).ToString() + "'.")
        End Function



        'creates a real type of a Nothing object 
        Private Shared Function CreateNullObjectType(ByVal otype As Object) As Object

            If TypeOf otype Is Byte Then
                Return VBConvert.ToByte(0)
            ElseIf TypeOf otype Is Boolean Then
                Return VBConvert.ToBoolean(False)
            ElseIf TypeOf otype Is Long Then
                Return VBConvert.ToInt64(0)
            ElseIf TypeOf otype Is Decimal Then
                Return VBConvert.ToDecimal(0)
            ElseIf TypeOf otype Is Short Then
                Return VBConvert.ToInt16(0)
            ElseIf TypeOf otype Is Integer Then
                Return VBConvert.ToInt32(0)
            ElseIf TypeOf otype Is Double Then
                Return VBConvert.ToDouble(0)
            ElseIf TypeOf otype Is Single Then
                Return VBConvert.ToSingle(0)
            ElseIf TypeOf otype Is String Then
                Return VBConvert.ToString("")
            ElseIf TypeOf otype Is Char Then
                Return VBConvert.ToChar(0)
            ElseIf TypeOf otype Is Date Then
                Return Nothing
            Else
                Throw New NotImplementedExceptio