We frequently run into trouble because project/package references in our solution are misconfigured (e. g. improperly requiring a specific version). I'd like to write a simple NUnit test to check for these kinds of cases so we can catch them early. Ideally, I'd use reflection over the assemblies rather than parsing the csproj file myself. Is this possible? Can all information from a csproj file be obtained via reflection on the compiled assembly?
You can get the reference of a particular assembly by calling Assembly.GetReferencedAssemblies, which will return the AssemblyName's that are referenced. This includes both name and version.
Assembly a = Assembly.ReflectionOnlyLoadFrom(fileName);
var references = a.GetReferencedAssemblies();
We have a large solution with about 30 projects. We also have some common code utilities and as part of that utility class we have included a GetAssemblyVersionInfo method that returns the version info of that assembly. However, we want to get the Assembly Version Info of the assembly for the project not the utility DLL. Is there any way of having a utility function that returns the version info of another assembly based on execution and not passing around filenames?
EDIT:
For those who are curious, I solved it using:
System.Reflection.Assembly.GetCallingAssembly().GetName().Version
If you have the assembly name, you can dynamically load it into the current AppDomain to retrieve the version info.
Assembly.LoadFrom(string.Format("{0}.dll", "assemblyshortname")).GetName().Version
I think you should use GetEntryAssembly() instead of GetCallingAssembly().
I have a rather strange project where I need to check the assemblies of the projects included as references in my project to see if they contain a certain Type. As far as I can tell the only way to see which projects are in my solution is to parse the solution file - which I can't do at runtime since I don't have it.
Does anyone know a way to see, at runtime, which assemblies are in the project file?
To check the referenced assemblies in your project assembly at runtime, you need to use Reflection.this.GetType().Assembly.GetReferencedAssemblies()
Can I reference two versions of a dll in the same project without putting them in the GAC?
Thanks
You've got two problems. First one is getting your app to compile. You've got two assembly references that contain types with the same namespace name and type name, the compiler won't know which one to choose. You solve that by using "extern alias", it lets you rename the namespace of one of the assemblies. Review this question for further help.
The second problem is the one you ask about. Without the GAC, you need to help the CLR finding the correct DLL. You must put the DLLs in a separate directory, say a subdirectory of your build directory, so that the CLR cannot find them. Use a post build event to create this directory and copy the DLLs into them. Give them distinct names.
Then implement the AppDomain.CurrentDomain.AssemblyResolve event. The CLR will fire it when it cannot find the DLLs you've hidden. Use Assembly.LoadFrom() to load and return the assembly it asks for. The e.Name property has the full assembly name, use the AssemblyName class to parse that string and retrieve the Version property.
Referring to an assembly without putting it into GAC means copying the dll in the bin folder of the project. And you cannot have two dlls of same name in the bin folder.
You cannot put reference of the same assembly twice.
If you create a class library that uses things from other assemblies, is it possible to embed those other assemblies inside the class library as some kind of resource?
I.e. instead of having MyAssembly.dll, SomeAssembly1.dll and SomeAssembly2.dll sitting on the file system, those other two files get bundled in to MyAssembly.dll and are usable in its code.
I'm also a little confused about why .NET assemblies are .dll files. Didn't this format exist before .NET? Are all .NET assemblies DLLs, but not all DLLs are .NET assemblies? Why do they use the same file format and/or file extension?
ILMerge does merge assemblies, which is nice, but sometimes not quite what you want. For example, when the assembly in question is a strongly-named assembly, and you don't have the key for it, then you cannot do ILMerge without breaking that signature. Which means you have to deploy multiple assemblies.
As an alternative to ilmerge, you can embed one or more assemblies as resources into your exe or DLL. Then, at runtime, when the assemblies are being loaded, you can extract the embedded assembly programmatically, and load and run it. It sounds tricky but there's just a little bit of boilerplate code.
To do it, embed an assembly, just as you would embed any other resource (image, translation file, data, etc). Then, set up an AssemblyResolver that gets called at runtime. It should be set up in the static constructor of the startup class. The code is very simple.
static NameOfStartupClassHere()
{
AppDomain.CurrentDomain.AssemblyResolve += new ResolveEventHandler(Resolver);
}
static System.Reflection.Assembly Resolver(object sender, ResolveEventArgs args)
{
Assembly a1 = Assembly.GetExecutingAssembly();
Stream s = a1.GetManifestResourceStream(args.Name);
byte[] block = new byte[s.Length];
s.Read(block, 0, block.Length);
Assembly a2 = Assembly.Load(block);
return a2;
}
The Name property on the ResolveEventArgs parameter is the name of the assembly to be resolved. This name refers to the resource, not to the filename. If you embed the file named "MyAssembly.dll", and call the embedded resource "Foo", then the name you want here is "Foo". But that would be confusing, so I suggest using the filename of the assembly for the name of the resource. If you have embedded and named your assembly properly, you can just call GetManifestResourceStream() with the assembly name and load the assembly that way. Very simple.
This works with multiple assemblies, just as nicely as with a single embedded assembly.
In a real app you're gonna want better error handling in that routine - like what if there is no stream by the given name? What happens if the Read fails? etc. But that's left for you to do.
In the rest of the application code, you use types from the assembly as normal.
When you build the app, you need to add a reference to the assembly in question, as you would normally. If you use the command-line tools, use the /r option in csc.exe; if you use Visual Studio, you'll need to "Add Reference..." in the popup menu on the project.
At runtime, assembly version-checking and verification works as usual.
The only difference is in distribution. When you deploy or distribute your app, you need not distribute the DLL for the embedded (and referenced) assembly. Just deploy the main assembly; there's no need to distribute the other assemblies because they're embedded into the main DLL or EXE.
Take a look at ILMerge for merging assemblies.
I'm also a little confused about why .NET assemblies are .dll files. Didn't this format exist before .NET?
Yes.
Are all .NET assemblies DLLs,
Either DLLs or EXE normally - but can also be netmodule.
but not all DLLs are .NET assemblies?
Correct.
Why do they use the same file format and/or file extension?
Why should it be any different - it serves the same purpose!
You can embed an assembly (or any file, actually) as a resource (and then use the ResourceManager class to access them), but if you just want to combine assemblies, you're better off using a tool like ILMerge.
EXE and DLL files are Windows portable executables, which are generic enough to accomodate future types of code, including any .NET code (they can also run in DOS but only display a message saying that they're not supposed to run in DOS). They include instructions to fire up the .NET runtime if it isn't already running. It's also possible for a single assembly to span across multiple files, though this is hardly ever the case.
Note ILMerge doesn't work with embedded resources like XAML, so WPF apps etc will need to use Cheeso's method.
There's also the mkbundle utility offered by the Mono project
Why do they use the same file format and/or file extension?
Why should it be any different - it serves the same purpose!
My 2ยข bit of clarification here: DLL is Dynamic Link Library. Both the old style .dll (C-code) and .net style .dll are by definition "dynamic link" libraries. So .dll is a proper description for both.
With respect to Cheeso's answer of embedding the assemblies as resources and loading them dynamically using the Load(byte[]) overload using an AssemblyResolve event handler, you need to modify the resolver to check the AppDomain for an existing instance of the Assembly to load and return the existing assembly instance if it's already loaded.
Assemblies loaded using that overload do not have a context, which can cause the framework to try and reload the assembly multiple times. Without returning an already loaded instance, you can end up with multiple instances of the same assembly code and types that should be equal but won't be, because the framework considers them to be from two different assemblies.
At least one way that multiple AssemblyResolve events will be made for the same assembly loaded into the "No context" is when you have references to types it exposes from multiple assemblies loaded into your AppDomain, as code executes that needs those types resolved.
https://msdn.microsoft.com/en-us/library/dd153782%28v=vs.110%29.aspx
A couple of salient points from the link:
"Other assemblies cannot bind to assemblies that are loaded without context, unless you handle the AppDomain.AssemblyResolve event"
"Loading multiple assemblies with the same identity without context can cause type identity problems similar to those caused by loading assemblies with the same identity into multiple contexts. See Avoid Loading an Assembly into Multiple Contexts."
I would suggest you to try Costura.Fody. Just don't forget to Install-Package Fody before Costura.Fody (in order to get the newest Fody!)