vb.net COM DLL 示例，实现了所有 VB6 X86 数据类型的对应

在VB.NET中写个例子实现所有VB6 X86数据类型的对应：string,long,Single等

以下是一个完整的 VB.NET COM DLL 示例，实现了所有 VB6 X86 数据类型的对应：

完整的 COM 类实现

vbnet 复制代码

Imports System.Runtime.InteropServices

<ComClass(VB6Compatible.ClassId, VB6Compatible.InterfaceId, VB6Compatible.EventsId)>
<ComVisible(True)>
Public Class VB6Compatible

#Region "COM GUIDs"
    ' 请替换为实际的GUID（使用Tools -> Create GUID生成）
    Public Const ClassId As String = "12345678-1234-1234-1234-123456789ABC"
    Public Const InterfaceId As String = "12345678-1234-1234-1234-123456789ABD"
    Public Const EventsId As String = "12345678-1234-1234-1234-123456789ABE"
#End Region

#Region "构造函数"
    Public Sub New()
        MyBase.New()
    End Sub
#End Region

#Region "字符串类型 (String)"
    ' VB6: Function ProcessString(input As String) As String
    Public Function ProcessString(ByVal input As String) As String
        Return "Processed: " & input
    End Function

    ' VB6: Sub ModifyString(ByRef text As String)
    Public Sub ModifyString(ByRef text As String)
        text = "Modified: " & text
    End Sub

    ' VB6: Function ConcatenateStrings(a As String, b As String) As String
    Public Function ConcatenateStrings(ByVal a As String, ByVal b As String) As String
        Return a & " " & b
    End Function
#End Region

#Region "整数类型"
    ' VB6 Integer (16位) - 对应 VB.NET Short
    ' VB6: Function AddIntegers(a As Integer, b As Integer) As Integer
    Public Function AddIntegers(ByVal a As Short, ByVal b As Short) As Short
        Return CShort(a + b)
    End Function

    ' VB6 Long (32位) - 对应 VB.NET Integer
    ' VB6: Function AddLongs(a As Long, b As Long) As Long
    Public Function AddLongs(ByVal a As Integer, ByVal b As Integer) As Integer
        Return a + b
    End Function

    ' 明确使用 MarshalAs 指定
    Public Function AddIntegersExplicit(
        <MarshalAs(UnmanagedType.I2)> ByVal a As Integer,
        <MarshalAs(UnmanagedType.I2)> ByVal b As Integer) _
        As <MarshalAs(UnmanagedType.I2)> Integer
        Return a + b
    End Function
#End Region

#Region "浮点类型"
    ' VB6 Single - 对应 VB.NET Single
    ' VB6: Function AddSingles(a As Single, b As Single) As Single
    Public Function AddSingles(ByVal a As Single, ByVal b As Single) As Single
        Return a + b
    End Function

    ' VB6 Double - 对应 VB.NET Double
    ' VB6: Function AddDoubles(a As Double, b As Double) As Double
    Public Function AddDoubles(ByVal a As Double, ByVal b As Double) As Double
        Return a + b
    End Function
#End Region

#Region "货币类型 (Currency)"
    ' VB6 Currency - 对应 VB.NET Decimal
    ' VB6: Function AddCurrency(a As Currency, b As Currency) As Currency
    Public Function AddCurrency(ByVal a As Decimal, ByVal b As Decimal) As Decimal
        Return a + b
    End Function

    ' VB6: Function CalculateTotal(price As Currency, quantity As Long) As Currency
    Public Function CalculateTotal(ByVal price As Decimal, ByVal quantity As Integer) As Decimal
        Return price * quantity
    End Function
#End Region

#Region "布尔类型"
    ' VB6 Boolean - 对应 VB.NET Boolean
    ' VB6: Function IsPositive(value As Long) As Boolean
    Public Function IsPositive(ByVal value As Integer) As Boolean
        Return value > 0
    End Function

    ' VB6: Sub ToggleFlag(ByRef flag As Boolean)
    Public Sub ToggleFlag(ByRef flag As Boolean)
        flag = Not flag
    End Sub
#End Region

#Region "日期类型"
    ' VB6 Date - 对应 VB.NET Date
    ' VB6: Function AddDays(startDate As Date, days As Long) As Date
    Public Function AddDays(ByVal startDate As Date, ByVal days As Integer) As Date
        Return startDate.AddDays(days)
    End Function

    ' VB6: Function GetCurrentDate() As Date
    Public Function GetCurrentDate() As Date
        Return Date.Now
    End Function
#End Region

#Region "变体类型 (Variant)"
    ' VB6 Variant - 对应 VB.NET Object
    ' VB6: Function ProcessVariant(input As Variant) As Variant
    Public Function ProcessVariant(ByVal input As Object) As Object
        If input Is Nothing Then
            Return "Null input"
        ElseIf TypeOf input Is String Then
            Return "String: " & input.ToString()
        ElseIf TypeOf input Is Integer Then
            Return CInt(input) * 2
        ElseIf TypeOf input Is Double Then
            Return CDbl(input) * 1.5
        Else
            Return "Unknown type: " & input.GetType().Name
        End If
    End Function
#End Region

#Region "字节类型 (Byte)"
    ' VB6 Byte - 对应 VB.NET Byte
    ' VB6: Function AddBytes(a As Byte, b As Byte) As Byte
    Public Function AddBytes(ByVal a As Byte, ByVal b As Byte) As Byte
        Return CByte((a + b) Mod 256)
    End Function
#End Region

#Region "数组类型"
    ' VB6 数组 - 需要明确指定 MarshalAs
    ' VB6: Function SumIntegerArray(arr() As Integer) As Long
    Public Function SumIntegerArray(
        <MarshalAs(UnmanagedType.SafeArray, SafeArraySubType:=VarEnum.VT_I2)> 
        ByVal arr() As Short) As Integer
        
        Dim sum As Integer = 0
        For Each item As Short In arr
            sum += item
        Next
        Return sum
    End Function

    ' VB6: Function ProcessStringArray(arr() As String) As String
    Public Function ProcessStringArray(
        <MarshalAs(UnmanagedType.SafeArray, SafeArraySubType:=VarEnum.VT_BSTR)> 
        ByVal arr() As String) As String
        
        Return String.Join(", ", arr)
    End Function
#End Region

#Region "可选参数和默认值"
    ' VB6: Function CalculateWithOptional(amount As Double, Optional taxRate As Double = 0.1) As Double
    Public Function CalculateWithOptional(ByVal amount As Double, 
                                        Optional ByVal taxRate As Double = 0.1) As Double
        Return amount * (1 + taxRate)
    End Function

    ' VB6: Sub MethodWithMultipleOptionals( _
    '   ByVal required As String, _
    '   Optional ByVal optional1 As Long = 10, _
    '   Optional ByVal optional2 As String = "default")
    Public Sub MethodWithMultipleOptionals(ByVal required As String,
                                         Optional ByVal optional1 As Integer = 10,
                                         Optional ByVal optional2 As String = "default")
        ' 方法实现
    End Sub
#End Region

#Region "ByRef 参数示例"
    ' VB6: Sub IncrementByRef(ByRef value As Long)
    Public Sub IncrementByRef(ByRef value As Integer)
        value += 1
    End Sub

    ' VB6: Sub SwapDoubles(ByRef a As Double, ByRef b As Double)
    Public Sub SwapDoubles(ByRef a As Double, ByRef b As Double)
        Dim temp As Double = a
        a = b
        b = temp
    End Sub
#End Region

#Region "复杂示例 - 综合使用多种类型"
    ' VB6: Function CalculateOrderTotal( _
    '   ByVal unitPrice As Currency, _
    '   ByVal quantity As Long, _
    '   ByVal discountRate As Double, _
    '   ByVal taxExempt As Boolean) As Currency
    Public Function CalculateOrderTotal(ByVal unitPrice As Decimal,
                                      ByVal quantity As Integer,
                                      ByVal discountRate As Double,
                                      ByVal taxExempt As Boolean) As Decimal
        
        Dim subtotal As Decimal = unitPrice * quantity
        Dim discounted As Decimal = subtotal * CDec(1 - discountRate)
        
        If Not taxExempt Then
            Return discounted * 1.08D ' 8% 税
        Else
            Return discounted
        End If
    End Function
#End Region

End Class

项目设置要求

在 AssemblyInfo.vb 中添加：

vbnet 复制代码

Imports System.Runtime.InteropServices

<Assembly: ComVisible(True)>
<Assembly: Guid("你的项目GUID")>
<Assembly: AssemblyVersion("1.0.0.0")>
<Assembly: AssemblyFileVersion("1.0.0.0")>

编译设置

项目属性 → 应用程序 → 程序集信息 → 勾选"使程序集 COM 可见"
项目属性 → 编译 → 勾选"注册 COM 互操作"
项目属性 → 签名 → 勾选"为程序集签名"，选择或创建强名称密钥文件

在 VB6 中的调用示例

vbnet 复制代码

Dim obj As New YourDLL.VB6Compatible
Dim result As Variant

' 字符串操作
Dim text As String
text = obj.ProcessString("Hello")
obj.ModifyString text

' 数值计算
Dim sumInt As Integer
sumInt = obj.AddIntegers(10, 20)

Dim sumLong As Long
sumLong = obj.AddLongs(1000, 2000)

Dim total As Currency
total = obj.CalculateTotal(19.99, 5)

' 布尔和日期
Dim isPos As Boolean
isPos = obj.IsPositive(-5)

Dim newDate As Date
newDate = obj.AddDays(Date, 7)

' 变体类型
Dim varResult As Variant
varResult = obj.ProcessVariant("Test")
varResult = obj.ProcessVariant(100)

这个示例涵盖了 VB6 X86 中所有主要数据类型的对应关系，并提供了完整的实现和调用示例。