Import C# Class

Question

I'm (very) new to C#, and I need to know how to import classes.

In Java, I could just say:

package com.test;
class Test {}

And then in some other class:

package com.test2;
import com.test.Test;

How could I do this in C#?

Calculation

In C# you import namespaces, not classes. If the class you are working in is in the same namespace, you don't need to do anything. If its in a different namespace and you are using Visual Studio, just type the name of the class and use the smart tag drop down to add the appropriate using to the top of the class file. See the existing using statements for how to include namespaces. – Haggai

possible duplicate of Using a class file/reference it? – Kuhlman

@Kuhlman I don't understand that, sorry. It's probably really, really simple and I'm just too stupid to figure it out. – Calculation

Grab CLR via C#, skip the first two chapters, and read. It'll take you an afternoon and you'll be 1000% better off for it. – Cadmus

Answer 1

Importing namespaces is accomplished in C# with the using directive:

using com.test;

However, there is no way, currently, to import a class. Importing classes, however is a new feature which is being introduced in C# 6 (which will come with Visual Studio 2015).

In C#, namespaces are the semi-equivalent of Java's packages. To declare the namespace, you just need to do something like this:

namespace com.test
{
    class Test {}
}

If the class is declared in a separate assembly (such as a class library), simply adding the using directive is not enough. You must also add a reference to the other assembly.

Lion

So how would I declare the package in C#? – Calculation

using statement is for the IDisposable pattern. This is called a using directive. – Invitatory

this answer here may be relevant, i'm not sure https://mcmap.net/q/526437/-import-a-static-method – Tom

"You must also add a reference to the other assembly." OK, and how do I do this, plesae? – Gibraltar

@Gibraltar I hate to make this more confusing for you, but that really depends what IDE you're using and what type of reference you want to add. For instance, if you're using Visual Studio for Windows and you want to add a reference to another project, right click on the project file and choose Add > Project Reference. Many libraries are available via the NuGet package manager. – Lion

Answer 2

I don't come from a Java background, but I come from a Python, C/C++ background where I always used something like "import" or "#include" and it always felt pretty simple.

But I want to share what I have learned so that others after me don't have to go through the same confusion. To give an example, I am going to show how to create a SHA256 instance.

using System.Security.Cryptography; //this is the namespace, which is what you import; this will be near the top of documentation you read
using static System.Security.Cryptography.SHA256; //this is an additional class inside the namespace that you can use; this will be in the "derived" section of documentation

AlgorithmHash sha = SHA256.Create(); //I am not entirely sure why, but the declaration needs to be on the same line as the instantiation

I have attached the HashAlgorithm documentation for reference: https://learn.microsoft.com/en-us/dotnet/api/system.security.cryptography.hashalgorithm?view=net-5.0.

Mann