Brackets around classname

15y837Azure

Hi,

Does anyone know why the class RuntimeType is referencing the same class name but in brackets? as below...

RuntimeType type = (RuntimeType) base.GetType();

13 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes15y ago
Accepted answer
The link you've just found applies to VB.NET where you can use a keyword as an ordinary identifier if you place square brackets around it. For example:

   Dim [Me] As Integer = 3

Here 'Me' is an ordinary integer variable and not the keyword 'Me' which means the same as 'this' in C#.

C# has a similar feature where the keyword is preceded by @:

   int @this = 3;

Needless to say, this is normally very poor programming practice and should only be used in exceptional circumstances.

Here's an example which uses casting between base and derived classes:

using System;

class Sype
{
   public void MyMethod()
   {
   Console.WriteLine("Hello from Sype.MyMethod");

   }
}

class RTT : Sype
{
   new public void MyMethod() // hides Sype.MyMethod
   {
   Console.WriteLine("Hello from RTT.MyMethod");
   }
}

class Test
{
   static void Main()
   {
   RTT rtt = new RTT();
   Sype s = rtt; // implicit conversion
   s.MyMethod(); // calls Sype.MyMethod
   RTT rtt2 = (RTT)s; // explicit conversion
   rtt2.MyMethod(); // calls RTT.MyMethod
   Console.ReadKey();
   }
}
Sam Hobbs15y ago
Thank you. I sure don't remember seeing colon dash (":-") before this web site. I probably have a little bit. That however is drifting from this topic so I won't dwell on it here.

Also, so as to not dwell too far off topic, I hope it is sufficient to say that it often helps to be clear about what is meant.

You have certainly answered the question much more thoroughly than I could.
Vulpes15y ago
There is a tendency in Britain to call '(' and ')' brackets - see, for example, http://en.wikipedia.org/wiki/Bracket

Sometimes I call them brackets and other times I call them parentheses though I would accept that the latter is preferable from an IT standpoint.

Also sometimes I call '{' and '}' curly braces rather than curly brackets which someone once told me was 'more correct'.

I was taught at school to use a colon (:) to introduce a list starting on the same line, and to use colon dash (:-) if the list started on the following line. I've no idea whether this is gramatically correct or not but it's served me well over the years :)
Sam Hobbs15y ago
You two are British, right? So is it a British thing to call them brackets? I have always seen them called parentheses.
- () parentheses
- [] square brackets
- {} curly brackets
People can get confused by terminology different from everyone else. I was quite surprised to see the quote "Usually you use brackets to differentiate" .... but then I was not surprised that the word brackets was refering to square brackets.

If the English have redefined English, then is there someplace where the new definitions exist? I especially need to know about correct punctuation, since as editor in this web site, I always change ":-" to ":"; am I incorrect?
15y ago
Thanks Vulpes,

RTT rtt2 = (RTT)s; // explicit conversion - Is the part the part I needed to know, what with the brackets around the class name, I should of known better! : )
15y ago
Vulpes I think I have the answer:-

"Usually you use brackets to differentiate a Method, property, variable, parameter or other name from a keyword.

For example, you could make a parameter to a method be something like "Me" or "Overloads." Then you'd need to put brackets around it in the method declaration and everywhere you use it.

You can generally avoid the brackets if you pick better names"

Regards,
15y ago
Ok Thanks,

For arguements sake how could I re factor my code in the most simplist form in order to enable me to use the () around the class... for test purposes...

Regards,
Vulpes15y ago
You have a couple of problems there.

Firstly, static methods have no concept of the 'current' instance, remembering that they refer to the class as a whole. This means that you can't call an instance method from a static method; nor can you use 'this' or 'base'.

Secondly, even if you placed your code in an instance method, it still wouldn't work. It would only work if your Sype class inherited from the Type class but, as the latter is abstract, Sype would need to implement a whole bunch of abstract members which isn't a practical proposition.

The RuntimeType class does all this but, as it's internal to mscorlib.dll, it can't be accessed directly from your code except by using reflection.
15y ago
Vuples,

Just been trying to recreate the Polymorphic process myself but with no luck...

This is what im trying:-

RTT rtt = (RTT)base.GetType();

The RTT class inherits from a class name Sype which contains the following public abstract void GetType() { }

It continues to say "Keyword base is not available in a static method"

I have tried changing the GetType method to static and non static but neither work?

Regards
15y ago
Perfect I fully understand, thanks for your quick responses and great answers Vulpes :)
Vulpes15y ago
You couldn't do it like that because GetType() is an instance method rather than a static method.

So, you need an actual instance to call it and here 'base' is used to represent the base class instance.

The brackets are needed because base.GetType() returns a Type reference (even though it's a RuntimeType) and you therefore need to cast it to RuntimeType to use it as such.

Polymorphic OO programming is great, eh ;)
15y ago
Thanks for your answer...

So could it also be RuntimeType type = RuntimeType.GetType(); or are the brackets there because its the same class type?
Vulpes15y ago
Well, it depends in which class that declaration appears - let's call it C.

What the line is first doing is obtaining the Type object of C's base class, using the GetType() method which all classes inherit from System.Object.

Now, RuntimeType is an internal class within mscorlib.dll which inherits from the Type class. So, the second thing which the line is doing is casting the Type object to RuntimeType so it can be assigned to the RuntimeType variable, type.

This suggests that the Type object for C's base class must have been a RuntimeType in the first place, otherwise the cast wouldn't work. In other words, C's base class must be RuntimeType and C must therefore be a derived class of it.