Suppose that at the top of my *.cs file, I am including some dependencies:
using System;
using System.Collections.Generic;
using System.IdentityModel.Tokens.Jwt;
using System.Linq;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Threading.Tasks;
Is it possible to also display version numbers here as shown below?
using System; //1.0.1
using System.Collections.Generic; //22.0.1
using System.IdentityModel.Tokens.Jwt; //3.56.2
etc
No, you can't. This is because C# and .NET is not like Java, TypeScript and other languages where the concept of namespaces, packages and libraries are combined - in .NET they're entirely separate: multiple packages can include the same library DLL file, and multiple library DLLs can contribute towards shared and different namespaces.
For example, the System namespace has its members in mscorlib.dll, System.dll, System.Core.dll, and others. None of these assemblies belong to any particular package as they're part of the BCL in your CLR implementation. Furthermore, anyone is free to declare their own types in namespace System.
With respect to "packages": the CLR is completely unaware of them: they're a design-time concern; instead all it cares about is what DLL files to link. You don't have to use NuGet packages at all (.NET developers survived just fine for the first 13 years without a built-in package manager).
Note that NuGet allows you to have multiple DLL files a single package, and the package author does not need to "own" (legally or otherwise) the DLLs contained within either, which means multiple NuGet packages can share the same assembly DLL, and those DLLs could share namespaces.
I take issue with these words of yours:
I am including some dependencies:
Remember, C# is not TypeScript - despite syntactic similarities (like C compared to C++) they're very different - it isn't appropriate to refer to namespace imports as "including dependencies" - it's just syntax - whereas in TypeScript the statement import { Foo } from './bar' is more than just syntax as it will invoke the runtime platform's package/module import system, whereas using in C# is an entirely inert statement that simply saves you from typing global::The.Full.Namespace.Name every time you use an identifier.
Related
I'm used C# -some- but not recently.
I've got this header from some code, and it calls a custom non-system library, (Dynastream.Fit, at the bottom), but I need to know how to tell the program where it resides so it can compile. Pretty sure the library is in the SDK I downloaded, just need to find it. This is the FitSDK from ANT+.
using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Diagnostics;
using Dynastream.Fit;
You need to add the dll of Dynastream.Fit to your project Reference folder by right clicking the reference folder -> add reference -> Browse -> choose the dll; unless you have already installed the assembly in GAC.
I'm writing a C# Console Application that is targeted towards .Net 4.5. I want to use Xaml Services to save and read a List data structure to file. I'm using VS 2013 Pro.
The .net doc's say Xaml has been in .NET since 4.0(?) I have my projected targeted to 4.5, but even with 4.0, 4.5.1, 4.6, and 4.6.1... same missing assembly reference. I'm doing a
using System;
using System.Collections.Generic;
using System.IO;
using System.Xaml; // <-- this is getting the assembly error
using System.Xml;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
But that is where the missing reference is getting the error...
I've used it before in Win Forms. It is that maybe it's excluded for console applications? Or am I missing something that Xaml Class depends on before using that assembly?
Could it be that you did not add a project reference to the assembly "System.Xaml.dll"? The Xaml functionality is not contained in the assemblies which are included in a new VS console project by default. (Right-Click on the "References" entry of the project, then select "Add References", then browse to "Framework" and look for System.Xaml, which refers to the dll of that name).
A namespace however does not necessarily correspond uniquely to an assembly, so you might require even more assemblies. If you know which types you need, you can browse the MSDN documentation for looking which assembly might still be required.
When looking at a solution with multiple projects:
1) Why do we add a reference to the other project? Can't we just use inheritance?
2) After we add the reference by using Visual Studio, why do we have to add the project to the namespace system? For example: using myReferenceProject; I thought that the IDE would do that.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using myReferenceProject;
using System.Data.SqlClient;
using System.Data;
1) why we give reference to the other project? cant we just use inheritance???
They're two completely different concepts.
Adding a reference to another assembly basically says, "I want to be able to use some of this code. Please make the compiler aware that this code exists, and optionally copy it into the output directory so that it's present at execution time too."
How would you expect to use inheritance to create a class derived from some type if the compiler has no knowledge of that type?
2) after we give the reference by using the visual studio IDE why we have to add the project to the namespace system???
Because assemblies and namespaces are different concepts too. A using directive simply says to the compiler "When I refer to type Foo within my code, look in these namespaces to try to resolve it." That type could come from any of the assemblies you've referenced.
It's really important that you understand the difference between assemblies and namespaces. Even though they're often named similarly (Foo.Bar.dll often provides types in the namespace Foo.Bar) they're conceptually different.
The project is a self sufficent compilable unit, that has to compile into the valid assembly file. That's why you need esplicitly specifiy which referencies every project needs in order to be able to compile separately from others.
There is no any inheritance concept on projects level.
1) why we give reference to the other project? cant we just use inheritance?
This question makes no sense. What does inheritance have to do with project references. Can you elaborate?
2) after we give the reference by using the visual studio IDE why we have to add the project to the namespace system?
Because there's an inherent difference between an assembly referencing another assembly (which is what happens when you add a reference to the project) and the language knowing where to find a class which is what happens when you use the using directive in a file.
For example, suppose you create a class in your project called TextBox. Then in another file you want to use that class. How would the language know whether you are referring to your custom TextBox class or another one in a referenced assembly? The answer to that question is namespaces. By fully-qualifying the class name with its namespaces, you tell the compiler which class you're using.
The using directive is a way to specifying the namespace once per file instead of every time you use the class (or other classes in that namespace). So if you need to reference your TextBox class multiple times within a single file, you wouldn't want to have to write this every time:
MyCodebase.MyAssembly.MyNamespace.MyOtherNamespace.SomethingElse.TextBox
Instead, you include a using directive of the entire namespace, so you only have to write this:
TextBox
I am using IKVM to wrap a java application into a dll. I am not particularly familiar with IKVM so I apologize in advance for not providing enough information. Anyway, I am using a c# library that makes a call to a dll created by IKVM. However the library I am using appears to require both IKVM.OpenJDK.ClassLibrary and IKVM.OpenJDK.Core. The only problem is both of these libraries contain java.util, which causes a namespace ambiguity for any class in java.util (Vectors, hastables, etc). I cannot fine a way to reference all instances of objects found in the java.utils class to explicitly use either ClassLibrary or Core. Is there anyway to reference a namespace to instruct my library to use one or the other for java.util calls?
In the current version of IKVM there is no IKVM.OpenJDK.ClassLibrary. It look like that you mix different versions of IKVM.
Is there a way to reference a namespace globally across the whole solution?
So instead of having these lines in every code file:
using System;
using MyNamespace;
having to declare them only once, and every code file would use them.
Btw I am using Visual Studio.
No, C# doesn't have this concept. Each source file is independent in this respect. (And if the using directives are in a namespace declaration, those are independent from other using directives in peer namespace declarations, too. That's a pretty rare case though in my experience.)
You don't need ReSharper to change what gets included in a new class though. You can use the Visual Studio templates.
EDIT: Just to clarify the point about using directives within namespaces, suppose we had (all in one file):
using Foo;
namespace X
{
using Bar;
// Foo and Bar are searched for code in here, but not Baz
}
namespace Y
{
using Baz;
// Foo and Baz are searched for code in here, but not Bar
}
Usually I only have one namespace declaration in a file, and put all the using directives before it.
No, this is not possible.
If you're using ReSharper, you can set an option to include specific using directives in every new file you create though.
From this SO question and follow-up blog post. You can edit the Visual Studio default templates.
To do this, look at the file in this zip : [Program Files][Visual Studio]\Common7\IDE\ItemTemplates\CSharp\Code\1033\Class.zip
and modify the Class.cs file as needed. Additionally, Visual Studio may have cached this file here :
[Program Files][Visual Studio]\Common7\IDE\ItemTemplatesCache\CSharp\Code\1033\Class.zip
In C# 10.0 you can use Global Usings.
global using System;
global using MyNamespace;
No, you can not reference a namespace globally across the whole solution in .NET or .NET CORE.
But you can use project wise namespace globally in solution. this feature will be available from c#10/.NET 6. currently it's in preview but it will be released in NOV 2021
=========Project level .NET 6 global using namespace=========
Create a class file at root of the project e.g GlobalNamespace.cs
global using System;
global using System.Linq;
global using System.Text.RegularExpressions;
global using System.Threading.Tasks;
Then you don't need to declare using namespace in other .cs files of the project which are already declared globally.
As others have mentioned Visual Studio Templates are the way to go.
Note that simply adding a using statement to your template will not ensure that the compiler can resolve your types. So, if you are adding a using statement for MyNamespace in every class you may need to add an assembly reference to your project as well. See the C# FAQ for more information.
One trick I miss as a newb to CSharp is to look at the "refences" (in VS), to right click and "Add New Reference". This is especially handy when combining mulitple projects where I have made some generic class for reuse elsewhere.