Advertisement
Advertisement


How to cast Object to its actual type?


Question

If I have:

void MyMethod(Object obj) {   ...   }

How can I cast obj to what its actual type is?

2012/09/02
1
122
9/2/2012 7:18:28 AM

Accepted Answer

If you know the actual type, then just:

SomeType typed = (SomeType)obj;
typed.MyFunction();

If you don't know the actual type, then: not really, no. You would have to instead use one of:

  • reflection
  • implementing a well-known interface
  • dynamic

For example:

// reflection
obj.GetType().GetMethod("MyFunction").Invoke(obj, null);

// interface
IFoo foo = (IFoo)obj; // where SomeType : IFoo and IFoo declares MyFunction
foo.MyFunction();

// dynamic
dynamic d = obj;
d.MyFunction();
2012/09/02
195
9/2/2012 7:22:54 AM

I don't think you can (not without reflection), you should provide a type to your function as well:

void MyMethod(Object obj, Type t)
{
    var convertedObject = Convert.ChangeType(obj, t);
    ...
}

UPD:

This may work for you:

void MyMethod(Object obj)
{
    if (obj is A)
    {
        A a = obj as A;
        ...
    } 
    else if (obj is B)
    {
        B b = obj as B;
        ...
    }
}
2012/09/02

How about JsonConvert.DeserializeObject(object.ToString());

2019/11/11

In my case AutoMapper works well.

AutoMapper can map to/from dynamic objects without any explicit configuration:

public class Foo {
    public int Bar { get; set; }
    public int Baz { get; set; }
}
dynamic foo = new MyDynamicObject();
foo.Bar = 5;
foo.Baz = 6;

Mapper.Initialize(cfg => {});

var result = Mapper.Map<Foo>(foo);
result.Bar.ShouldEqual(5);
result.Baz.ShouldEqual(6);

dynamic foo2 = Mapper.Map<MyDynamicObject>(result);
foo2.Bar.ShouldEqual(5);
foo2.Baz.ShouldEqual(6);

Similarly you can map straight from dictionaries to objects, AutoMapper will line up the keys with property names.

more info https://github.com/AutoMapper/AutoMapper/wiki/Dynamic-and-ExpandoObject-Mapping

2017/05/10

This method might not be the most efficient but is simple and does the job.

It performs two operations: firstly it calls .ToString() which is basiclly a serialization, and then the deserialization using Newtonsoft nuget (which you must install).

public T Format<T>(Object obj) =>
    JsonConvert.DeserializeObject<T>(obj.ToString());
2020/02/21

If your MyFunction() method is defined only in one class (and its descendants), try

void MyMethod(Object obj) 
{
    var o = obj as MyClass;
    if (o != null)
        o.MyFunction();
}

If you have a large number in unrelated classes defining the function you want to call, you should define an interface and make your classes define that interface:

interface IMyInterface
{
    void MyFunction();
}

void MyMethod(Object obj) 
{
    var o = obj as IMyInterface;
    if (o != null)
        o.MyFunction();
}
2012/09/02