Is possible to cast a variable to a type stored in another variable?

Question

This is what I need to do:

object foo = GetFoo();
Type t = typeof(BarType);
(foo as t).FunctionThatExistsInBarType();

Can something like this be done?

Answer 1

No, you cannot.

C# does not implement Duck typing.

Implement an interface and cast to it.

P. S. However there are attempts to do it. Look at Duck Typing Project.

Answer 2

You can use the Convert.ChangeType method.

object foo = GetFoo(); 
Type t = typeof(string);
string bar = (string)Convert.ChangeType(foo, t);

Answer 3

Your original question was flawed in that you ask to treat a variable as a type which is not known at compile time but note that you have string defined on the left hand side when you declare your variable. C# as of 3.5 is statically typed.

Once dynamic is available you could do something like this:

dynamic foo = GetFoo();
foo.FunctionThatExistsInBarType();

For when you don't know what the type is but you know it will always support the instance method FunctionThatExistsInBarType();

for now you are forced to use reflection (or code gen which really amounts to much the same thing but more expensive up front and faster later).

// any of these can be determined at runtime
Type t = typeof(Bar);
string methodToCall = "FunctionThatExistsInBarType";
Type[] argumentTypes = new Type[0];
object[] arguments = new object[0];
object foo;
// invoke the method - 
// example ignores overloading and exception handling for brevity
// assumption: return type is void or you don't care about it
t.GetMethod(methodToCall, BindingFalgs.Public | BindingFlags.Instance)
    .Invoke(foo, arguments);