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?

Answer 1

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());

Answer 2

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;
        ...
    }
}

Answer 3

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();
}

Answer 4

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

Answer 5

Casting to actual type is easy:

void MyMethod(Object obj) {
    ActualType actualyType = (ActualType)obj;
}

Answer 6

If multiple types are possible, the method itself does not know the type to cast, but the caller does, you might use something like this:

void TheObliviousHelperMethod<T>(object obj) {
    (T)obj.ThatClassMethodYouWantedToInvoke();
}

// Meanwhile, where the method is called:
TheObliviousHelperMethod<ActualType>(obj);

Restrictions on the type could be added using the where keyword after the parentheses.