如何使用反射从静态方法调用实例类方法 [英] How to call an instance class method from a static method with reflection

问题描述

namespace ClassLibraryB {
    public class Class1 {
        public void Add(int ii, int jj)
        {
            i = ii;
            j = jj;
            result = i + j;
        }
        public void Add2()
        {
            result =  i + j;
        }
    }
}

这被静态调用并给我一个答案

This gets called statically and gives me an answer

ClassLibraryB.Class1 objB = new ClassLibraryB.Class1();
objB.Add(4, 16);
objB.Add2();
kk = objB.result;
textBox1.Text += "Addition =" + kk.ToString() + "
";

但是，当我尝试使用下面的方法调用 dll 时，它失败了，因为它不是静态的

However when I try to call the dll using below it fails with since it is not static

Assembly testAssembly = Assembly.LoadFile(strDLL);
Type calcType = testAssembly.GetType("ClassLibraryB.Class1");
object calcInstance = Activator.CreateInstance(calcType);
PropertyInfo numberPropertyInfo = calcType.GetProperty("i");
numberPropertyInfo.SetValue(calcInstance, 5, null);
PropertyInfo numberPropertyInfo2 = calcType.GetProperty("j");
numberPropertyInfo2.SetValue(calcInstance, 15, null);
int value2 = (int)numberPropertyInfo.GetValue(calcInstance, null);
int value3 = (int)numberPropertyInfo2.GetValue(calcInstance, null);
calcType.InvokeMember("Add2",BindingFlags.InvokeMethod | BindingFlags.Instance | BindingFlags.Public,
    null, null, null);
PropertyInfo numberPropertyInfo3 = calcType.GetProperty("result");
int value4 = (int)numberPropertyInfo3.GetValue(calcInstance, null);

我只需要确切地知道我必须对 dll 类进行哪些更改才能在此处调用它

I just need to know exactly what changes I have to make to the dll class to be able to call it here

推荐答案

您必须将类型的实例传递给 InvokeMember

You must pass an instance of the type to InvokeMember

calcType.InvokeMember("Add2", flags, null, calcInstance, null);

<小时>

如果您要创建插件，正确的做法是拥有三个程序集.

---

If you are creating a plug-in, the right thing to do is to have three assemblies.

1. 包含插件接口声明的类库 (dll)
2. 包含接口(插件)实现的类库 (dll)
3. 加载插件的可执行文件 (exe)

接口 DLL 被其他两个组件引用.您需要三个程序集，因为插件不应该知道关于您的应用程序的任何信息，并且应用程序除了它的接口之外不应该知道关于您的插件的任何信息.这使得插件可以互换，不同的应用程序可以使用相同的插件.

The interface DLL is referenced by the two other components. You need three assemblies because the plug-in should not know anything about your application and the application should not know anything about your plug-in other than its interface. This makes the plug-ins interchangeable and different applications can use the same plug-in.

接口组件Calculator.Contracts.dll

public interface ICalculator
{
    int Add(int a, int b);
}

<小时>

插件实现Calculator.dll

public class Calculator : ICalculator
{
    public int Add(int a, int b)
    {
        return a + b;
    }
}

<小时>

现在您可以加载插件并在应用程序(exe)中以键入的方式使用它:

---

Now you can load the plug-in and use it in a typed way in the application (exe):

Assembly asm = Assembly.LoadFrom(strDLL);
string calcInterfaceName = typeof(ICalculator).FullName;
foreach (Type type in asm.GetExportedTypes()) {
    Type interfaceType = type.GetInterface(calcInterfaceName);
    if (interfaceType != null &&
        (type.Attributes & TypeAttributes.Abstract) != TypeAttributes.Abstract) {

        ICalculator calculator = (ICalculator)Activator.CreateInstance(type);
        int result = calculator.Add(2, 7);
    }
}

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