Namespace

14y2.5kVisual Basic .NET

There are many namespaces in C# for example

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

I know System namespace eliminates need to have System name in every WriteLine() method. I wish to know is there any technique to decide appropriate name space for a program. Is there any articles about this?

16 Replies

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

Sam Hobbs14y ago
I said you need to refer to the documentation of the class. There are other possibilities but documentation is the most useful, or at least should be. You would normally use the documentation to determine what to reference and the namespace could then be determined using many techniques. I think all the other suggestions here end up going to the documentation.
Vulpes14y ago
As Satish said, you need to have included a reference to the dll which includes the type for this feature to work. The reason is that intellisense only knows about types which are either declared in your program or are referenced by your program.

As it happens BigInteger, which is a new type in .NET 4.0, is included in System.Numerics.dll so you need to add a reference to that first before you can use it.

To add a reference, right click on References in Solution Explorer, select Add Reference from the dropdown, locate and select System.Numerics.dll under the .NET tab and OK it.

Once you've done that, when you place the cursor on BigInteger and press Ctrl .(dot), the smart tag should appear allowing you to select:

using System.Numerics;

The program should then build and run.
14y ago
I tried the above technique but couldn't get the idea. For example how to find out appropriate using directive for the following program by using above technique.

public class Example
{
public static void Main()
{
BigInteger[] values = { 2, 100, BigInteger.Pow(2, 64) };
foreach (var value in values)
Console.WriteLine(Math.Exp(BigInteger.Log(value) / 2));
}
}
Vulpes14y ago
Type the name of some class into Visual Studio, let's say XmlSerializer.

Leaving the cursor over the word, press and hold down the Ctrl key and then press the . (dot) key.

You should see a smart tag open up, with a using directive for this class:

using System.Xml.Serialization;

which will be inserted for you in its proper place if you select it.

Other info will also be shown such as the fully qualified name of the type:

System.Xml.Serialization.XmlSerializer

Notice that this only works for classes which don't already have a suitable using directive.
14y ago
I don't have any clue how begin with Satish Tip if you can advice me step by step approach it is highly desirable.
Vulpes14y ago
That's a very good tip, Satish.

I didn't know that and I'm sure it will be useful to Maha :)
Satish Bhat14y ago
TIP : If you have already referenced the dll which contains the namespace, Visual Studio helps you to find (add) the namespace by using Ctrl + DOT (.) Keys when the cursor is on the Class name.
Vulpes14y ago
The only things you need (or may need) to look up in that piece of code are:-

1. Collection which is a collection base class in the System.Collections.ObjectModel namespace:

http://msdn.microsoft.com/en-us/library/ms132397.aspx

2. Converter which is a delegate in the System namespace:

http://msdn.microsoft.com/en-us/library/kt456a2y.aspx

As the ConverterCollection class is being defined in the program, then it can't be a framework class.

To be able to write a C# program in a reasonable amount of time, you need to have a familiarity with the C# language itself and at least the basic framework namespaces and classes. Armed with that knowledge, you can usually find anything else you may need from the documentation (or by googling) as types which have related functionality tend to be grouped in the same namespace.
Sam Hobbs14y ago
Where is the documentation of ConverterCollection? You read about it somewhere; where? I could guess at the answer to that, but this question is about what to do in general, not just ConverterCollection specifically. So the answer is that you look at the documentation and if you found that class in an article then the article should provide the answer to the question of where the class is or how to find where it is.
14y ago
Suppose take following program for example this program is using two namespaces those are
using System;
using System.Collections.ObjectModel;

Suppose I have to write this program from scratch how to decide what are the namespaces I have to use.

using System;
using System.Collections.ObjectModel;

class ConverterCollection : Collection
{
private Converter convert;

public ConverterCollection(Converter convert)
{
this.convert = convert;
}

protected override void InsertItem(int index, T item)
{
base.InsertItem(index, convert(item));
}
}

public class MainClass
{
public static void Main()
{
ConverterCollection c = new ConverterCollection(
delegate(string s) { return s.ToUpper(); });
c.Add("Hello");
c.Add("World!");

foreach (string s in c)
Console.WriteLine(s);
}
}
Sam Hobbs14y ago
I am not sure what I am supposed to look at in Console.Clear() but I assume you are asking about the Console functions such as Console.Clear(). Note that the "Console" class is part of .Net and that web site probably assumes you know that. Look at the top of the sample source code; it says "using System;". If you go to the MSDN Library and type "console" in the search box then you will find the Console Class; do you see where it says:

Namespace: System
Vulpes14y ago
I thought you were asking how to decide what to call your own namespaces :)

If you just want to know what namespace a framework type belongs to then, as Sam, says you need to consult the MSDN documentation. This will also tell you what dll it's in, in case you need to add a reference to that dll as well as a 'using' directive for the namespace.
14y ago
There are many programs in the net but those programs are using different namespaces extensively. I wish to know how to decide which program needs what namespaces. (please see http://www.java2s.com/Code/CSharpAPI/System/ConsoleClear.htm)
Sam Hobbs14y ago
I am not sure what your question is. If Vulpes answered your question that that is good. Perhaps you are asking what namespace to use if you need to use a class that has already been developed by Microsoft or someone else. If so then the answer is different. The answer to this other question is essentially that you get the information from the documentation of the class.
14y ago
Thank you for your help.
Vulpes14y ago
If you're writing a class library for other developers to use, then you should follow the MSDN guidelines here:

http://msdn.microsoft.com/en-us/library/893ke618(VS.71).aspx

Otherwise, you can call your namespaces what you like as long as they don't clash with those in the .NET Framework or with third party libraries you may use.

A good practice to avoid any clashes would be to always prefix your namespaces with your name or your company name.