如何通过后期绑定从VB.Net调用位于C#DLL内的方法 [英] How to call a method located inside a C# DLL, from VB.Net, with late binding

问题描述

我无法掌握各种"Init"，"Accumulate" ...方法的工作方式，以允许从VB.Net代码调用位于DLL内的方法.

I can't get a grip on how the various "Init", "Accumulate" ... methods work, to enable calling a method located inside a DLL, from VB.Net code.

假设调用方法具有以下签名:

Let's say the method to call has the following signature :

public double ComputeMeanPosition(ref SortedList<DateTime, double> posByTime)

请问我如何使用该方法的实际示例，或者只是给我一些提示，以了解如何将参数实际传递给该方法，调用它并获取结果?

Would you please kindly point me to an actual example of the use of the methods, or simply give me a few hints as how to actually pass the parameters to the method, call it and fetch the results ?

@Olivier Jacot-Descombes:我肯定用名称空间名称作为类名称的前缀，但是仍然无法访问该对象.实际上，令您惊讶的是，您的建议没有涉及通过装入的DLL的内省显示的以下方法:

@Olivier Jacot-Descombes: I definitely prefix the class name by the namespace name, but yet fail to be able to reach the object. In fact I am surprised that your kind suggestion does not involve the following methods, displayed through introspection of the loaded DLL :

Type: MyClassName
        Method: Void Init()
        Method: Void Accumulate(System.Data.SqlTypes.SqlDouble, System.Data.SqlTypes.SqlDateTime, System.Data.SqlTypes.SqlBoolean)
        Method: Void Merge(MyClassName)
        Method: System.Data.SqlTypes.SqlDouble Terminate()
        Method: Void Write(System.IO.BinaryWriter)
        Method: Void Read(System.IO.BinaryReader)
        Method: Boolean Equals(System.Object)
        Method: Int32 GetHashCode()
        Method: System.String ToString()
        Method: System.Type GetType()

编辑

事实上，我有一个类似于以下代码的代码，它可以成功地检查DLL并从中获取几种类型和方法，从而为我要调用的方法提供了以下结果.

In fact I have a code similar to the following one, that successfully manages to inspect the DLL and gets several types and methods out of it, giving the following results above for the method I would like to call.

这是代码

        For Each oneModule As Reflection.Module In useAssembly.GetLoadedModules()
            Console.WriteLine("   - " & oneModule.Name)
            For Each oneType As System.Type In oneModule.GetTypes()
                Console.WriteLine("     Type: " & oneType.Name)
                For Each oneField As Reflection.FieldInfo In oneType.GetFields()
                    Console.WriteLine("        Field: " & oneField.ToString())
                Next oneField

                For Each oneMethod As Reflection.MethodInfo In oneType.GetMethods()
                    Console.WriteLine("        Method: " & oneMethod.ToString())

                    [[ ADD "Invoke" here ?]]
                Next oneMethod
            Next oneType
        Next oneModule

最后，似乎[[...]]位于应调用Invoke方法以调用我选择的方法的地方，但这就是我遇到的问题……我可以吗?需要在调用对象之前先建立对象吗?我应该如何传递参数?如何获得结果?

At the end, it seems that the [[...]] is at the place where the Invoke method should be called to call the method of my choice, but that is where I'm stuck... Would I need to build an object before calling it ? How should I pass it the parameters ? How to get the result ?

推荐答案

类似的方法应该起作用:

Something like this should work:

using System;
using System.Reflection;
using System.IO;

public class MainClass
{
      public static int Main(string[] args)
      {
           Assembly a = null;
           try
           {
                a = Assembly.Load("YourLibraryName");
           }
           catch(FileNotFoundException e)
               {Console.WriteLine(e.Message);}

           Type classType = a.GetType("YourLibraryName.ClassName");

           object obj = Activator.CreateInstance(classType);

           object[] paramArray = new object[1];    
           paramArray[0] = new SortledList<DateTime, double>();
           MethodInfo mi = classType.GetMethod("ComputeMeanPosition");
           mi.Invoke(obj, paramArray);

           return 0;
       }
 }

对于VB.NET:

Imports System
Imports System.Reflection
Imports System.IO

Public Class MainClass
    Public Shared Function Main(args As String()) As Integer
        Dim a As Assembly = Nothing
        Try
            a = Assembly.Load("YourLibraryName")
        Catch e As FileNotFoundException
            Console.WriteLine(e.Message)
        End Try

        Dim classType As Type = a.[GetType]("YourLibraryName.ClassName")

        Dim obj As Object = Activator.CreateInstance(classType)

        Dim [paramArray] As Object() = New Object(0) {}
        [paramArray](0) = New SortledList(Of DateTime, Double)()
        Dim mi As MethodInfo = classType.GetMethod("ComputeMeanPosition")
        mi.Invoke(obj, [paramArray])

        Return 0
    End Function
End Class

经过测试，此方法有效:

Tested and this worked:

 Dim a As Assembly = Nothing
    Try
        a = Assembly.Load("TestLib")
    Catch ex As FileNotFoundException
        Console.WriteLine(ex.Message)
    End Try

    Dim classType As Type = a.[GetType]("TestLib.Class1")

    Dim obj As Object = Activator.CreateInstance(classType)

    Dim [paramArray] As Object() = New Object(0) {}
    [paramArray](0) = New SortedList(Of DateTime, Double)()
    Dim mi As MethodInfo = classType.GetMethod("ComputeMeanPosition")
    mi.Invoke(obj, [paramArray])

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