C# : how do I differentiate between built-in types and non built-in types?

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The C# built-in types web page only listed the bottom types as built-in Value types and built-in Reference tyes. But aren't the succeeding types Timer, Math, IComparable, File so on and so forth also built-in types? Since they too were provided by the Microsoft team for any developer to use.

The following table lists the C# built-in value types:

- bool
- byte
- sbyte
- char
- decimal
- double
- float
- int
- uint
- nint
- nuint
- long
- ulong
- short
- ushort

The following table lists the C# built-in reference types:

- object
- string
- dynamic

What I have tried:

How to diffentiate between built-in and non built-in types
Visual studio

Posted 15-Aug-21 8:59am

Matildemona

Updated 16-Aug-21 9:01am

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[no name] 15-Aug-21 15:42pm

Timer, etc, are "classes" in the ".NET framework library"; which for all intents is an "add on"; derived from the "built-in" types; to aid in development; so you don't have to build them.

Matildemona 15-Aug-21 15:59pm

A colleague of mine (we're both new to C#) advised me that built-in types are types that are natively in the C# language (no need to import any namespace to use them) while other types provided by Microsoft are not built-in types since a namespace needs to be imported in order to use those types in code. As that true?

PIEBALDconsult 15-Aug-21 17:16pm

No namespace ever needs to be "imported" in C#.
Do you mean add a reference to a different DLL?

Matildemona 15-Aug-21 17:53pm

No, I did I mean importing a namespace. Because isn't the using directive meant for importing a namespace into a source code file in c#?

PIEBALDconsult 15-Aug-21 20:50pm

Which is never necessary in order to use the types defined within it.

And of course it does nothing to the source code file.

Matildemona 15-Aug-21 16:39pm

What are those types called if they are not called built-in types?

[no name] 16-Aug-21 0:49am

As you noticed, the built-ins are all "value" types; i.e. "primitives".

The "other" things, are "reference" types; more "complex" types; made up of primitives and other complex types.

A nut or a bolt is a "primitive". Put something together with nuts, bolts and other parts to make say a "clock", you've now established a pattern for a clock; i.e. a "class" of clock. Those are the "reference types".

Values are like the numbers in a formula; a reference type is (like) the formula.

Matildemona 16-Aug-21 1:12am

I actually came across this youtube video https://www.youtube.com/watch?v=JvCyfx0ilIk which sated plain and simple that a "built-in type" is an alias (e.g. int, string) to a type defined in the System namespace. And as suggested by one user, built-in types (aliases) are built into the C# language while the types themselves are built into the .Net Framework. Is there any truth to that?

PIEBALDconsult 15-Aug-21 17:18pm

Do you mean the types in the Base Class Library?

4 solutions

Solution 3

I think you'll find this diagram useful: [^]. From this article: [^].

Of course, you will also want to consider what the current MS "official" classification is: [^].

NameSpaces are a taxonomy: they organize/classify/group different collections of functionality and data, and, you can create your own to control semantic scope, or organize your own work.

With your (deeper) level of interest in the C# language and .NET, let me recommend a book by the language creators: [^]

The C# Programming Language (Covering C# 4.0), Fourth Edition
by Anders Hejlsberg (Author), Mads Torgersen (Author), Scott Wiltamuth (Author), Peter Golde (Author)
2010 Addison-Wesley Professional
ISBN: 9780132484718

This remarkable book includes annotations by some of the most brilliant C# programmers; many of them played a role in creating/evolving C# and .NET: Brad Abrams, Joseph Albahari, Krzysztof Cwalina, Jesse Liberty, Eric Lippert, Christian Nagel, Vladimir Reshetnikov, Marek Safar, Chris Sells, Peter Sestoft, Jon Skeet, and Bill Wagner.

Posted 15-Aug-21 14:39pm

BillWoodruff

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Matildemona 16-Aug-21 0:07am

Thanks. I will make sure to check out that book. I was also recommended C# 8.0 in a nutshell by O'Reilly.

Solution 4

Another potential answer:

"
C# provides a set of predefined struct types called the simple types. The simple types are identified through reserved words, but these reserved words are simply aliases for predefined struct types in the System namespace, as described in the table below.
" -- Types - C# language specification | Microsoft Docs[^]

Posted 16-Aug-21 9:01am

PIEBALDconsult

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OriginalGriff · Accepted Answer · 2021-08-15T09:57:00

Solution 1

No, built in types are the "basic building blocks" of the language (or strictly speaking, the Framework) and do not require any special treatment or using statements:

C#

public class Program
    {
	public static void Main()
    	{
    	int x = 95;
    	int y = 3;
    	string str = ((double) x / (double) y).ToString("F2");
        }
    }

Will compile and run (though it will not be in any way useful ...)
Everything else needs something to say what Namespace it comes from: even somethign as simple as adding

C#

Console.WriteLine(str);

To make it do anything even vaguely useful requires the System namespace, normally via

C#

using Sytem;

At the top of the file.
The File class needs System.IO for example, and so on, and so on.

Basically, if its isn't on the "built in list", it's a framework (or external) addon!

Posted 15-Aug-21 9:57am

OriginalGriff

Comments

Matildemona 15-Aug-21 16:36pm

A colleague of mine advised me with something similar "built-in types are types that are natively in the C# language (no need to import any namespace in order to use them) while other types provided by Microsoft are not built-in types since a namespace needs to be imported in order to use those types in code." Is that fundementally the same as what you said?

OriginalGriff 15-Aug-21 16:53pm

That gets a bit ... grey area ...
Are they "native to C#"? Or "native to the .NET framework"? Bear in mind that the same list applies to VB as well, but that the C# keywords are names which are interchangeable with teh .NET versions on which they depend.
https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/built-in-types

I'd hesitate to say either they are or they aren't "built in to C#" since C# the language and .NET the framework are pretty much inseparable! :laugh:

Matildemona 15-Aug-21 17:22pm

Just to be on the safe side. I'll just jot down that built-in types are native to C# / .net framework :laugh:

But i'm curious, if those types I mentioned to aren't called built-in types then what are they called? (e.g. types that you or I create, per say, are called user-defined types).

PIEBALDconsult 15-Aug-21 17:26pm

Right, no types are actually built into the language, they're all part of the Framework / Base Class Library.
But some .net types have aliases to make the most common types easier to reference.
Otherwise, a developer can define his own aliases with a directive such as [ using datetime=System.DateTime ; ] , which is essentially all the types [ int , decimal , string , etc. ] are.

Matildemona 15-Aug-21 18:33pm

Are you saying that built-in types are built into the .net framework and not built into the C# language?

Dave Kreskowiak 15-Aug-21 19:39pm

There are no types built into the C# language. Hover the mouse over the int keyword and you'll notice its formal name is System.Int32. int is an alias for the Int32 type, which is a structure in the System namespace.

The name you may be looking for is "intrinsic types".

Dave Kreskowiak 15-Aug-21 21:34pm

That's because int is an alias to a fully qualified name for a type, System.Int32. Note, the namespace the type comes from is part of the qualified name.

int is an alias, not a type. The alias is built into C#. Alias' don't need a namespace.

Matildemona 15-Aug-21 22:02pm

It is obvious to me now that a "built-in type" is an "alias" (eg. int, char, object, string) to a type (eg. Int32, Char, Object, String) defined in the System namespace.

And as you stated "aliases" to those types are built into the C# langauge, thus, "built-in types" are built into the C# language. While the types themselves are built into the .Net Framework.

Would you say that is accurate?

OriginalGriff 16-Aug-21 4:56am

This is why I said it was rather "grey area" ...
C# is not like languages such as C, C++, Python, or even Cobol - it was designed at the same time as the framework so the two are interdependent (indeed, .NET is written in C#) and probably shouldn't be considered alone. C# has no data types "of it's own" so the only built in ones are really part of the framework is exists with. But ... to make things easier and more readable it provides "short cut" names to the framework types.

See what I mean? Separating them into "C# built in types" and ".NET types" isn't a clear cut thing. Just ignore it and move on - it really isn;t relevant to actual coding anyway! :laugh:

PIEBALDconsult · Accepted Answer · 2021-08-15T14:34:00

Solution 2

There is this list:
Built-in types - C# reference | Microsoft Docs[^]
but I still don't think the term "built-in" is quite the right term here.

"is an alias for the corresponding .NET type"

The .net framework has many types "built in", but the C# and VB languages do not.
At most I'd agree that there are a few type aliases upon which a few language elements depend -- such as when defining an enumerated type.

"System-provided type aliases" might be a more accurate term.

Other than that, perhaps you are looking for a list of which types are in System.dll or mscorlib.dll ?

Posted 15-Aug-21 14:34pm

PIEBALDconsult

Updated 15-Aug-21 14:47pm

v2

Comments

Matildemona 15-Aug-21 21:11pm

yes I agree built-in types could have been better explained, nevertheless, i'm bewildered as to what is actually built into the C# language and what is built into the .Net framework. I have been examining the use between int and Int32 in Visual Studio. While int requires no namespace to be imported in order to be utilized, using Int32 requires the importation of the System namespace. Does this mean aliases (e.g. int) are built into the C# language while the types themseleves (e.g. System.Int32) are built into the .Net framework (specifically in the .net class library)?

PIEBALDconsult 15-Aug-21 23:53pm

"using Int32 requires the importation of the System namespace" -- No, it does not.

int is simply an _alias_ for System.Int32 , the type _is_not_ built into the language.

Matildemona 16-Aug-21 0:00am

My mistake. Thank you for correcting me. But I will say it is clear to me now that a "built-in type" is an "alias" (eg. int, char, object, string) to a type (eg. Int32, Char, Object, String) defined in the System namespace.

And how Dave Kreskowiak stated "the 'aliases' to the types defined in the System namespace are built into the C# langauge". Thus, "built-in types" are built into the C# language. While the types themselves, the aliases correspond to, are built into the .Net Framework.

Would you say that is accurate?

PIEBALDconsult 16-Aug-21 0:04am

Closer to accurate, but I still think it's imprecise.

Matildemona 16-Aug-21 0:14am

Hopefully you have not lost interest in this post as I am well aware this has been dragging on. But what about the above is imprecise?

Having watched many video tutorials, anaylzing the documentations recommended, along with consideration to all the comments and solutions made in this post that was the conclusion I reached. But I am open for any corrections.