Question
It seems to me that any time I make a class library, all of its dependencies should just come with it. In other words, I would expect to just reference a .dll and go. After all, the .dll I reference builds just fine on its own.
Is this not the case? I reference all of a dependency's dependencies, in order to use it?
Looking forward to being enlightened about this.
Issue
To illustrate, here's an example.
ClassLibrary1 is a class library project, with one public class:
Class1.
ClassLibrary2 is another class library, in the same solution, with
one public class: Class1.
These two classes exist in their own namespaces.
However, ClassLibrary2 references ClassLibrary1, and ClassLibrary2.Class1 inherits from ClassLibrary1.Class1.
ConsoleApplication1 is a console app, in the same solution, that references only ClassLibrary2.
Up to this point, everything builds. Everything is the same framework.
However, when I attempt to initiate ClassLibrary2.Class1, I get a build error:
Error 1 The type 'ClassLibrary1.Class1' is defined in an assembly that
is not referenced. You must add a reference to assembly
'ClassLibrary1, Version=1.0.0.0, Culture=neutral,
PublicKeyToken=null'. ...\ConsoleApplication1\Program.cs 12 4 ConsoleApplication1
Code Snippets
namespace ClassLibrary1
{
public class Class1
{
public Class1() { }
}
}
...
namespace ClassLibrary2
{
public class Class1 : ClassLibrary1.Class1
{
public Class1() : base() { }
}
}
...
namespace ConsoleApplication1
{
using ClassLibrary2;
class Program
{
static void Main(string[] args)
{
// error mentioned previously in post is on following line
var a = new Class1();
}
}
}
I'll try to formulate an answer here. It helps to look at dependencies on the project level in VS and hopefully it will be more clear.
Suppose you have two projects, ProjectA and ProjectB in a solution. Both projects reference an assembly Important.dll. By reference here, I am referring to if you right click -> Add 'Reference' in a VS project. Suppose also, that ProjectA references ProjectB in our solution in VS. By this I mean, right click -> 'Add Reference' -> 'Solution' -> Pick Project B
What is actually going on? Remember, all a VS reference is a way to help the compiler find the .dll. At build time (compiling), VS will go through all the projects in the solution that are required to be built (you can see this in the Configuration Manager). It will notice that both ProjectA and ProjectB are set to build. Then it will look at all its direct dependencies in the references section by traversing the dependency tree. For all the VS references that are set to 'Copy local' (true by default), they will be sent to the build folder. So Important.dll will go to the build folder.. you probably knew that.
But ProjectA references ProjectB in VS. When you have a project that references another project in a solution, all you're really doing is pointing to the built .dll of that project... in this case ProjectB.dll. It's no different from antoher .dll. You can see this if you look at the references section under 'Path' in ProjectA... it'll be something like C:\users\jdwqdwqd\vs\ProjectB\ProjectB\bin\x64\ProjectB.dll. So this will be copied to the output folder as well.
I guess one might ask 'Won't Important.dll be copied twice along with ProjectB.dll?. VS gives you a lot of help here and will pick the correct .dll to copy.
Hope this helps.
Some more information:
https://msdn.microsoft.com/en-us/library/ez524kew.aspx
It's just the way C# works. The inheritance rules seem to be skewed. I'm working on a massive project at work, and I can use class libraries and namespaces across multiple files, but I have to reference them every time, regardless of inheritance. It's weird and annoying. Maybe they'll fix that soon.
Related
I am trying to determine which dlls my assemblies need to compile. I have two sample projects, Scratch and ScratchTest both in one solution. Here is Scratch's Program.cs:
using System.ServiceProcess;
namespace Scratch
{
public class A : ServiceBase
{
static void Main(string[] args)
{
}
}
}
Scratch has a reference to System.ServiceProcess.dll.
Here is ScratchTest's program.cs:
namespace ScratchTest
{
class Program
{
static void Main(string[] args)
{
Scratch.A o;
}
}
}
ScratchTest has to reference BOTH Scratch and System.ServiceProcess.dll. However, the resulting ScratchTest.dll has no reference to System.ServiceProcess.dll, only Scratch. I know this both by looking at
Assembly.GetReferencedAssemblies()
and by using .net reflector. So my question is, how can I tell that ScratchTest requires System.ServiceProcess.dll to compile? Especially considering SratchTest wouldn't necessarily want to reference all of Scratch's references because there might be some conflicting ones. Thanks, Eric
First thing is that the problem that you are facing is not specific to ServiceBase Class. It is pertaining to how exactly CLR detects the type dependencies for a C# program and loads the referenced assemblies. C# compiler is simply giving you an error in advance at compile time itself as the same will fail at run time also when CLR tries to run your program. Here is what I'm assuming while explaining the solution to your problem:
ScratchTest is your start-up project although you have defined two entry points in your solution as Main method is present in both "Scratch" and "ScratchTest" projects. To avoid confusion generally you should have only one main method (entry point) for your solution though it has no impact on your current problem.
Solution : When you refer class A in scratchTest project you are not referring only to class A but the class ServiceBase as well because class "A" is inheriting from it. So when compiler tries to compile your ScratchTest Project it tries to find the dependency types namely "A" and ServiceBase both in the assemblies that are currently referenced. The point of importance here is that CLR always tries to find the dependency types only in the assemblies whose reference is present directly in the manifest meta-data of the assembly itself which you are trying to load (which is ScratchTest in this case). Dependency types are NEVER searched in a recursive fashion the way you have structured your solution. Essentially expecting CLR to search a dependency type in all the referenced assemblies and in turn their referenced assemblies will be hell lot of performance impact at start-up of your .Net application.
At the same time the core .Net libraries like MsCorLib, System, System.Core, System.Data are usually referenced in most of the C# projects you create. Then considering the case otherwise had CLR implemented the logic of recursively finding the dependency types through referenced assemblies then it would have been making an extra effort by making a check every time whether it had already gone past a specific assembly or not while searching a dependency type which would have hurt start-up performance further.
To fix your code you can do following two things :
Add reference to System.ServiceProcess.dll to ScratchTest project as advised by the C# compiler.
OR
Use the class A in "ScratchTest" project itself as it already contains a reference to System.ServiceProcess.dll
I don't think you need to explicit call System.ServiceProcess on the test file.
The Test file is not using any reference to any method or class inside System.ServiceProcess, just using Scratch.
You do not need to requieres all the libraries that the referenced clases uses, just the one are currently used by your class.
So ScratchTest is only using Scrath and Scratch is using System.ServiceProcess.
I have solution with 3 projects.
SharingFilesTest have a file MainPage.xaml and the other two projects have this MainPage.xaml added as a link.
So, the issue is when I try to use any App.xaml.cs GLOBAL variable in MainPage.xaml.cs file it says "The name 'App' doesnot exist." only when I tried to Build Pro1 and Pro2. SharingFilesTest works fine
However, I have defined the same variable in all App.xaml.cs in the solution. I mean Pro1, Pro2 and SharingFilesTest all three have the same variable.
I haved tried referencing Pro1 and Pro2 in SharingFilesTest and then add Using statement for both Pro1 and Pro2. But still doesnt work as Pro1 doenst know Pro2 and vice versa.
It's usually better to share a view among multiple assemblies by moving that code into a separate class library that all your other assemblies can then reference. Linking the code file itself, as you've done in this case, is definitely not the preferred method.
That said... if you're determined to just link the exact code file, you'll need to move your global variable into a class which exists in the same namespace within each project. Your projects should therefore not reference each others' assemblies.
For example, you might add a file called Globals.cs which uses the same namespace in each project:
namespace SharedNS
{
public class Globals
{
public const int MyGlobalVar = 0;
}
}
The App.xaml.cs files, which should probably stay in the project-specific namespaces (e.g. Pro1, Pro2, SharingFilesTest) can reference the Globals object if needed.
I am creating a Visual Studio solution and am trying to add namespaces Kafka.Client, Kafka.Client.Producers.Parititioning, Kafka.Client.IntegrationTests, etc. to a program file I've created with a Main() method. I have Kafka.Client and Kafka.Client.IntegrationTests in the References of this program file as per Solution Explorer. The code is as follows:
using Kafka.Client;
using Kafka.Client.IntegrationTests;
using Kafka.Client.Producers.Partitioning;
using Kafka.Client.Utils;
using Kafka.Client.ZooKeeperIntegration;
namespace ConsoleApplication2 {
class Program {
static void Main(string[] args) {
//code here
}
}
}
The problem is that when I try to "Rebuild solution" or "debug solution", the aforementioned "using" lines give the error "The type or namespace name 'Kafka' could not be found (are you missing a using directive or an assembly reference?)" I've spent quite a long time on this and would appreciate some pointers about what I would need to do.
using doesn't actually "include" anything into your project. It just makes it so you don't always have to type out the full namespace. So the error is clearly in referencing the other project.
The Kafka project has to be built first. So first make sure you can successfully build the Kafka project.
if the Kafka is not in the same project, make sure you've add the the reference to the dll, and make sure "copy local" is true
to add the dll as a reference, right-click ConsoleApplication2 in the solution explorer, click add reference, then browse to and locate the actual dll output by the kafka project.
Sounds like these are separate class libraries or other projects. If that's the case, add a project reference from your main project and the using statements will then work.
The reason you want to add them as a project reference, and not a dll reference is that you'll likely switch back and forth from debug/release mode and you might end up with an outdated reference.
Thanks for trying to answer the questions. My problem was that the "Target application" was not the same for all the projects in my solution. Right-clicking on the referenced projects and selecting "Properties" enabled me to change the target application. Then I needed to rebuild the .dll files to run the program properly.
Background: I am a novice in C#, and use Visual Studios 2010 Express.
I have a class (let's call it myclass) which I want to use in multiple projects. I used to add classes with Project->Add Existing Item... Which creates a copy of myclass.cs.
Now I just found out that when I build the original myclass.cs it creates a myclass.dll and places it in the release folder of my project.
But when I try to use this DLL, I get the following error:
The type or namespace name 'myclass' could not be found(are you
missing a using directive or an assembly refference?
Which is weird to me, because I already have referenced it (it is also in the Reference folder of my Solution Explorer). And I already have added this to my code:
using myclass;
So what am I doing wrong?
Update: When I tried my old method (add existing item -> myclass.cs) the error message goes away. So it's not a matter of spelling things correctly.
Add the dll first:
Click on references in your project-explorer in visual studio and add your dll then you can use it as you expected it.
Add the reference in your project and check that the target Framework version of that assembly fits the project.
Check the namespaces inside the assembly and then use them like:
using YourAssemblyNamespace.class
Okay so I found the answer myself. It turns out that when you use the using function, it automatically searches for all public classes in the namespace you want to use.
If it can't find a public class, it refuses to recognize the DLL.
Furthermore, not specifying a class makes it internal.
So:
class myclass // internal!
private class myclass // private!
public class myclass // only this makes it visible for others!
Everything was okay after changing class myclass into public class myclass.
I have created another namespace in another project but within the same solution. When I type using this other namespace it shows up. But I cannot see any public class within that namespace. What's wrong ?
Since the type is public, this sounds as simple as a missing project reference between the two. Right click references and add a new reference, but watch that references shouldn't become circular (i.e. A <===> B, or A ===> B ===> C ===> A). Actually, the VS IDE doesn't let you do this, but it can be done (accidentally or purposefully) via the command-line tools.
You have to
reference the exporting assembly in the importing project
define 1 or more public classes in the exporting project.