In C#, is there any difference between using System.Object in code rather than just object, or System.String rather than string and so on? Or is it just a matter of style?
Is there a reason why one form is preferrable to the other?
views:
904answers:
7
+1
A:
string is an alias for global::System.String, and object for global::System.Object
Providing you have using System; in your class, String / string and Object / object are functionally identical and usage is a matter of style.
(EDIT: removed slightly misleading quote, as per Jon Skeet's comment)
Colin Pickard
2009-06-19 10:21:33
"String" with a capital letter doesn't have any meaning to the C# compiler or the C# language. "string" *always* corresponds to global::System.String. I don't know where the original author gets the notion that "String" has special meaning.
Jon Skeet
2009-06-19 10:26:00
because of Java
bobobobo
2009-06-20 03:37:13
A:
There are no difference. There is a number of types, called Primitive Data Types which are threated by compiler in style you mentioned.
Capitalized naming style is ISO naming rule. It's more general, common; forces the same naming rules for all objects in the source without exceptions such C# compiler has.
abatishchev
2009-06-19 10:21:37
That article is poorly written to use the word "primitive" there. If you look at the docs for Type.IsPrimitive you'll see: "The primitive types are Boolean, Byte, SByte, Int16, UInt16, Int32, UInt32, Int64, UInt64, IntPtr, UIntPtr, Char, Double, and Single." Note that this *doesn't* include string, decimal and object, but *does* include IntPtr and UIntPtr.
Jon Skeet
2009-06-19 10:23:49
(It also uses the word "object" in a pretty fast-and-loose way. It's a generally badly-written article, IMO.)
Jon Skeet
2009-06-19 10:24:41
A:
As of my knowledge, I know that it's a shortcut, it's easier to use string, rather than System.string.
But be careful there's a difference between String and string (c# is case sensitive)
Omar Abid
2009-06-19 10:22:55
A:
string (with the lowercase "s") is the string type of the C# language and the type System.String is the implementation of string in the .NET framework.
In practise there is no difference besides stylistic ones.
EDIT: Since the above obviously wasn't clear enough, there is no difference between them, they are the same type once compiled. I was explaining the semantic difference that the compiler sees (which is just syntactic sugar, much like the difference between a while and for loop).
Matthew Scharley
2009-06-19 10:25:05
-1 This is incorrect. string and System.String are entirely interchangeable. string is simply an alias for System.String
Simon P Stevens
2009-06-19 10:47:26
This is correct, and I never said they were different. string is a keyword that points at System.String. Perhaps I wasn't clear.
Matthew Scharley
2009-06-19 11:15:44
Actually, I was very clear, "In practise there is no difference..."
Matthew Scharley
2009-06-19 11:16:58
+17
A:
string is an alias for global::System.String. It's simply syntactic sugar. The two are exactly interchangable, and there'll be no difference in the compiled code.
Personally I use the aliases for variable names etc, but I use the CLR type names for names in APIs, for example:
public int ReadInt32() // Good, language-neutral
public int ReadInt() // Bad, assumes C# meaning of "int"
(Note that the return type isn't really a name - it's encoded as a type in the metadata, so there's no confusion there.)
Jon Skeet
2009-06-19 10:27:30
The remark about language neutrality for public APIs is very interesting indeed!
Paolo Tedesco
2009-06-19 10:31:05
Language neutrality for public APIs is how much of the .NET libraries work.
Justice
2009-06-19 11:21:04
You can usually spot a C# former VB programmer when they use String instead of string (not that it matters).
RichardOD
2009-06-19 11:23:48
I'm sure this is mentioned in another question, but I'll mention it for completeness. In CLR via C#, Jeffrey Ritcher recommends you always use the language neutral type names everywhere. However the defacto standard is as Jon describes.
RichardOD
2009-06-19 11:27:29
This does not make sense. What language neutrality are we talking about. Whether it is a public API or not when compiled no one can tell if you used string or String
Stilgar
2009-06-19 11:33:17
@Stilgar I wasn't referring to String. Look at my comment on Jon's answer here if it doesn't make sense- http://stackoverflow.com/questions/981434/can-anyone-give-me-a-really-good-reason-to-use-clr-type-names-instead-of-c-type
RichardOD
2009-06-19 11:37:19
@Stilgar: That's why my answer used int/Int32 rather than string/String. Yes, it doesn't matter for String/Object/Decimal/Double/Byte/SByte - but it does matter for all the rest.
Jon Skeet
2009-06-19 13:14:40
+1
A:
The object type is an alias for System.Object. The object type is used and shown as a keyword. I think it has something to do with legacy, but that's just a wild guess.
Have a look at this MSDN page for all details.
I prefer the use of the lowercased versions, but for no special reasons. Just because the syntax highlighting is different on these "basic" types and I don't have to use the shift key when typing...
Sorskoot
2009-06-19 10:34:28