使用反射实例化类并调用方法

Question

Below is my method to get a property value from a class object. How can I achieve the same by instantiating the class by passing the class name as String. After instantiating, I want to use the method 'LoadFromXmlData()' which is available on the same page. Can this be done?

 private string GetPropertyValue(string propName, string className)
    {
      Class1 _Class1;
      Class2 _Class2;
      Class3 _Class3; 

        if (className.Equals("Class1"))
        {

         _Class1 = new Class1();
         _Class1 = (Class1)Class1.LoadFromXmlData(typeof(Class1), myData.ToString());

          return _Class1.GetType().GetProperty(propName).GetValue(_Class1,   null).ToString();
        }
        else if (ActionClassName.Equals("TicketActionDef"))
        {
         _Class2 = new Class2();
         _Class2 = (Class2)Class2.LoadFromXmlData(typeof(Class2), myData.ToString());

         return __Class2.GetType().GetProperty(propName).GetValue(_Class2, null).ToString();
        }
        else
        {
         _Class3 = new Class3();
         _Class3 = (Class1)Class1.LoadFromXmlData(typeof(Class3), myData.ToString());

         return __Class3.GetType().GetProperty(propName).GetValue(_Class3, null).ToString();

        }

    }

I will load my DLL as below. How should I proceed after this. Please help, I am very new to reflection.

 Assembly assembly = Assembly.GetAssembly(typeof(MyAdapter));
 MyAdapter currentEventObject = (MyAdapter)assembly.CreateInstance(className);

Thanks

Answer 1

I'm not 100% sure I understand the full scope of what you're trying to achieve, but in order to instantiate a named class (make sure to include the fully qualified name; fullNamespace.className) and call a method and a property on it you can do it like this:

    private static string GetPropertyValue(Assembly assembly, string className, 
        string propertyName)
    {
        object instance = assembly.CreateInstance(className);
        Type classType = instance.GetType();
        MethodInfo method = classType.GetMethod("LoadFromXmlData");
        method.Invoke(instance, new object[] { classType, myData });
        PropertyInfo property = classType.GetProperty(propertyName);
        return property.GetValue(instance, null).ToString();
    }

This will call the LoadFromXmlData with the type of the class to be loaded and some xml data.

---

In order to avoid the reflection for calling the LoadFromXmlData method, you should create an interface that all dynamically loaded types must implement:

interface IXmlLoadable
{
   void LoadFromXmlData(Type type, string data);
}

Then the method call could be simplified into this:

((IXmlLoadable)instance).LoadFromXmlData(classType, myData));

---

If you are using C# 4, you could use the dynamic keyword to simplify the reflection work:

private static string GetPropertyValue(Assembly assembly, string className,     
   string propertyName)
{
        dynamic instance = assembly.CreateInstance(className);
        Type classType = instance.GetType();
        instance.LoadFromXmlData(classType, "<xml></xml>");
        PropertyInfo property = classType.GetProperty(propertyName);
        return property.GetValue(instance, null).ToString();
}

Answer 2

if it's an instance method, you can do

Object _Class1 = Type.GetType("Class1").GetConstructor(new Type[0]).Invoke(null);
Type.GetType("Class1").GetMethod("LoadFromXmlData" typeof (Class1).GetMethod("LoadFromXmlData").Invoke(_Class1, new[]{myData.ToString()});

Answer 3

I believe you would need to do something like this:

Type.GetType("Namespace.Class1").GetConstructor(new Type[] {}).Invoke(null);

"Namespace.Class1" is the assembly-qualified. For example, the assembly-qualified name for a class might look like this:

TopNamespace.SubNameSpace.ContainingClass+NestedClass, MyAssembly, Version=1.3.0.0, Culture=neutral, PublicKeyToken=b17a5c561934e089

Answer 4

I think you need to create the instance of the class using Activator.CreateInstance() method. And you can call the method directly in the object.

class Program
{
    static void Main(string[] args)
    {
        Assembly asm = Assembly.GetExecutingAssembly();
        Sample s1 = Activator.CreateInstance(typeof(Sample)) as Sample;
        s1.SayHello();
    }
}

public class Sample
{
    public void SayHello()
    {
        Console.WriteLine("Hello World");
    }
}