How to cast Object to its actual type?

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();

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;
        ...
    }
}

How about

JsonConvert.DeserializeObject<SomeType>(object.ToString());

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