CODEWITHSUNDEEP
c#.netreflectioncasting
Remus
Remus

Reputation: 179

.NET reflection cast to exact type

i wonder if there is a way to cast to exact type using system.reflection so that you will avoid doing explicit cast such as 

(System.DateTime)

for example

Assuming i would have a Dictionary such as 

Dictionary<propName, Dictionary<object, Type>>

and assuming i iterate over an object props list

foreach (var prop in @object.GetType().GetProperties())
{
       object propValue = propInfo.GetValue(@object, null);
       string propName = propInfo.Name;

       Dictionary<object, Type> typeDictionary = new Dictionary<object, Type>();
       Type propType = propInfo.GetValue(@object, null).GetType();
       typeDictionary[propValue ] = propType ;

       propsDictionary[propInfo.Name] = propValue;
}

I would like to do something like , cast to exact type using something like

// this part is only for guidelines 
// it should obtain the exact Type 
// ... but it returns a string of that type Namespace.Type
Type exactType = Dictionary[enumOfPropName][someValue] 
// this part should know the exact type Int32 for example and cast to exact 
var propX = (exactType)someValue

Is there any way of doing such thing and if so how can i obtain this? Also most of this code is just a guideline, an idea so please don't take it likely. Thank you all.

Upvotes: 0

Views: 4171

Answers (4)

MattC
MattC

Reputation: 4014

Once you know the type:

var x = 22;
var type = typeof(Int32);
var propX = Convert.ChangeType(x, type);

Or in your case:

object thing = 32;
var lookup = new Dictionary<string, Dictionary<object, Type>>();

lookup.Add("Test", new Dictionary<object, Type>());

lookup["Test"].Add(thing, typeof(Int32));

var propX = Convert.ChangeType(thing, lookup["Test"][thing]);

Caveats with this approach: Convert.ChangeType: For the conversion to succeed, value must implement the IConvertible interface...

Upvotes: 4

No&#233;mie Lord
No&#233;mie Lord

Reputation: 781

If I understand your question, you want to convert an object (in an object typed variable) to its actual type you have extracted thorough reflexion. If so, I beleive Convert.ChangeType could be of help to you. You can use it like this : 

var propX = Convert.ChangeType(someValue, exactType);

I am pretty casting requires you to know the type at compile-time, which is why you cannot cast with a Type variable (since it's only known at runtime).

Upvotes: 0

Theodoros Chatzigiannakis
Theodoros Chatzigiannakis

Reputation: 29233

  • An object's type is runtime information.
  • A variable's type is compile-time information.
  • Compile-time comes before runtime.

The conclusion here is that it's not possible to have a statically typed variable that matches the exact type of an arbitrary object instance, because doing so would require information that is not available yet.

As a workaround, consider making the variable dynamic and see what you can do from there.

Upvotes: 5

Marlon Vidal
Marlon Vidal

Reputation: 669

You will need to implement an implicit operator on the target class to the type you want

class Program
{
    static void Main(string[] args)
    {
        var a = new A() { property = "someValue" };
        string obj = (string)teste;
    }
}

class A
{
    public string property { get; set; }

    public static implicit operator string(A t)
    {
        if (t == null)
            return null;

        return t.property;
    }
}

Upvotes: -1

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