I have a type like this:
public class TypeValue { public Type Type { get; private set; } public object Value { get; private set; } } so I can do something like:
TypeValue tv = ... int count = (tv.Type) tv.Value; but the compiler is giving me this error:
The type or namespace name 'tv' could not be found (are you missing a using directive or an assembly reference?)
How do I achieve this?
No. How would the compiler be able to determine what type "Type" refers to at compile time? A "type" object is not the same thing as the name of a type that is used when performing a cast. For example, this doesn't work either:
// "typeof" returns a "Type" object. string foo = (typeof(string))SomeObj; You won't be able to use a static cast, but you can be sneaky and do this using reflection at runtime.
dynamic might also be an option, depending on what Joan is trying to do with the cast value.string text = tv.Value; would attempt to cast to string, and int count = tv.Value; would attempt to cast to int. And you can catch RuntimeBinderException to handle where tv.Value wasn't the right type. Note this is a simple cast: it will NOT attempt to e.g. parse a string into an integer, or call ToString() if the target is a string, nor will it consider conversion operators.Assignment you displayed cannot be done way you want. Types of objects on either sides of assignment operator must be equal (or right-hand object must be of type inheriting left-hand object type).
So, you cant do
Type1 obj1 = new Type1(); Type type = typeof(Type1); Type2 obj2 = (type)obj1; You could achieve functionality you want by making your class generic, or having a generic method for getting value. E.g.
public class TypeValue { public Type Type { get; private set; } public object Value { get; set; } public T GetValueAs<T>() { if (Value == null) return default(T); return (T)Value; } } TypeValue a = new TypeValue(); a.Value = 1; int b = a.GetValueAs<int>(); or even better
public class TypeValue<T> { public Type Type { get { return typeof(T); } } public T Value { get; set; } } TypeValue<int> a = new TypeValue<int>(); a.Value = 1; int b = a.Value; Type c = a.Type; 
int with him. He needs to get it dynamically from TypeValue.Type property.You should just do:
TypeValue tv = ... int count = (int) tv.Value; See, in the case where you know the type at compile-time (in this case you know that count is an int), then there's no point referring to tv.Type anyway. This helps illustrate why this doesn't make logical sense and thus is not possible.
count is always known, even if the type of tv.Value is not. Thus you can use a static cast. If you do not even know the type of count, then this entire situation doesn't apply as you cannot really do anything with the object anyway except pass it to someone else... who will eventually do a cast when the type is assumed.It's impossible to get a strongly-typed variable from System.Type and System.Object. Sometimes you can make your class generic like this:
public class TypeValue<T> { public T Value { get; private set; } } 