CODEWITHSUNDEEP
c#reflectionobjectprivatecasting
alhazen
alhazen

Reputation: 1915

C# Reflection - Casting private Object field

I have the following classes:

public class MyEventArgs : EventArgs
{
    public object State;

    public MyEventArgs (object state)
    {
        this.State = state;
    }

}

public class MyClass
{
     // ...

     public List<string> ErrorMessages 
     {
          get
          {
               return errorMessages;
          }
      }
}

When I raise my event, I set 'State' of the MyEventArgs object to an object of type MyClass. I'm trying to retrieve ErrorMessages by reflection in my event handler: 

 public static void OnEventEnded(object sender, EventArgs args)
 {
      Type type = args.GetType();
      FieldInfo stateInfo = type.GetField("State");
      PropertyInfo errorMessagesInfo = stateInfo.FieldType.GetProperty("ErrorMessages");

      object errorMessages = errorMessagesInfo.GetValue(null, null);

  }

But this returns errorMessagesInfo as null (even though stateInfo is not null). Is it possible to retrieve ErrorMessages ?

Edit: I should clarify that the event handler is in a different assembly, and I cannot reference the first assembly (that contains MyEventArgs and MyClass) for build issues.

Thank you

Edit: Solution 

FieldInfo stateInfo = args.GetType().GetField("State");
Object myClassObj = stateInfo.GetValue(args);
PropertyInfo errorMessagesInfo = myClassObj.GetType().GetProperty("ErrorMessages");
object errorMessagesObj = errorMessagesInfo.GetValue(myClassObj, null);
IList errorMessages = errorMessagesObj as IList;

Upvotes: 1

Views: 2023

Answers (4)

alhazen
alhazen

Reputation: 1915

Solution:

FieldInfo stateInfo = args.GetType().GetField("State");
Object myClassObj = stateInfo.GetValue(args);
PropertyInfo errorMessagesInfo = myClassObj.GetType().GetProperty("ErrorMessages");
object errorMessagesObj = errorMessagesInfo.GetValue(myClassObj, null);
IList errorMessages = errorMessagesObj as IList;

Upvotes: 0

MaK
MaK

Reputation: 93

An example....

PropertyInfo inf = ctl.GetType().GetProperty("Value");
errorMessagesInfo.GetValue(ClassInstance, null);




//And to set a value
    string value = reader[campos[i]].ToString();
    inf.SetValue(ctl, value, null);

Upvotes: 1

LBushkin
LBushkin

Reputation: 131646

You don't need reflection for this, just cast EventArgs to MyEventArgs and then you can access the ErrorMessages property:

 public static void OnEventEnded(object sender, EventArgs args) 
 { 
     MyEventArgs myArgs = (MyEventArgs)args;
     MyClass detail = (MyClass)myArgs.State;

     // now you can access ErrorMessages easily...
     detail.ErrorMessages....
 }

You should avoid using reflection for something where they types are fully known. Instead, you should use type casting to convert the reference to the types you expect. Reflection makes sense when the type information is dynamic, or not available at compile time in your code (which doesn't appear to be the case).

Upvotes: 2

Darin Dimitrov
Darin Dimitrov

Reputation: 1038710

You need to pass the instance of MyClass:

errorMessagesInfo.GetValue(someInstanceOfMyClass, null);

If the sender is of type MyClass that would mean:

errorMessagesInfo.GetValue(sender, null);

Upvotes: 0

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