My project is targeting to .NET 4.5. It doesn't use any new 4.5 methods, so it actually works fine on the machine with only .NET 4.0 installed.
This is all good until I added some extension methods and reflection. Then when I ran this .NET 4.5 program on the 4.0 machine, it failed with "System.TypeLoadException: Could not load type 'System.Runtime.CompilerServices.ExtensionAttribute' from assembly mscorlib". The famous ExtensionAttribute program that has been documented well here.
Another quick way to test this is to add the following line. Then the program will throw the exception when running on .NET 4.0 only.
Console.WriteLine(typeof(System.Runtime.CompilerServices.ExtensionAttribute).Assembly.FullName);
I'm wondering if there is a way to work around it. For example, the ILMerge (when using the correct /targetplatform option as documented in the link) actually changes the ExtensionAttribute from mscorlib to System.Core if the project is target to .NET 4.0 (with 4.5 installed). But it doesn't seem to work on the project targeted to .NET 4.5.
I know this is a long shot. But just want to see if anyone has other ideas since it was so close.
Thanks.
In general, this will not work. It does work in some cases since 4.5 is an in place replacement for 4.0, but it's not going to work in general. I've, personally, seen problems with types that have moved into different assemblies, and the bindings aren't setup correctly, just like you're seeing. The reflection types aren't the only types that were moved in 4.5.
My project is targeting to .NET 4.5. It doesn't use any new 4.5 methods, so it actually works fine on the machine with only .NET 4.0 installed.
If this is the case, you could just change your application to target .NET 4.0. This should allow it to run safely on a machine with only .NET 4 installed.
Related
I have a project in .Net 4.5, however when I try to add a framework reference all that is available to me are 4.0 options. Why is this happening and what can I do to get the 4.5 references options?
Thank you in advance.
That's another direct result of .NET 4.5 in place upgrading .NET 4.0. Th assembly version you saw in VS should not change, while the actual file version if you check in Windows Explorer updated.
This kind of design gives maximum compatibility to applications as they can load the new assemblies just as usual. Assume Microsoft changed the number to 4.5 as you desired, such applications would throw FileNotFoundException which can be quite harmful.
This would be a real pain to try to duplicate, so I'm hoping someone has a quick answer...
Suppose I have a .NET 4.0 application, with a reference to a .NET 2.0 library (SharpZipLib in this case). This of course works fine on a normal machine with .NET 2.0 and 4.0 installed.
If the server running this application has only .NET 4.0 and not 2.0 (or 3.0/3.5 etc.), what do I need to do to allow the .NET 2.0 library to run properly?
From what I've read, it looks like I may be able to put in a config setting for supportedRuntime, but I'm not quite understanding what exactly that does.
Will a config setting work, or would only .NET 4.0 libraries function in this environment?
(This is a hypothetical environment - I don't plan on ever having my own servers with 4.0 and not 2.0, but if someone is crazy enough to do it, I want to be able to support them).
Thanks
The CLR can load older assemblies in the .net 4.0 framework.
Here's a good read:
http://msdn.microsoft.com/en-us/magazine/ee819091.aspx
EDIT: updated quote from article. Particularly notice the bold
The .NET Framework 4 runtime—and all future runtimes—will be able to
run in-process with one another. While we did not back-port this
functionality to older runtimes (1.0 through 3.5), we did make sure
that 4 and beyond will be able to run in-process with any single older
runtime. In other words, you will be able to load 4, 5 and 2.0 in
the same process, but you will not be able to load 1.1 and 2.0 in the
same process. .NET Frameworks 2.0 through 3.5 all run on the 2.0
runtime and so have no conflicts with one another, as shown in Figure
2.
From http://neilblackburn.blogspot.com/2009/10/net-framework-40-backward-compatibility.html (and, transitively, http://mtaulty.com/CommunityServer/blogs/mike_taultys_blog/archive/2009/08/03/installing-net-framework-v4-0-and-running-net-2-0-3-0-3-5-3-5sp1-applications.aspx):
Now, I knew that you can’t just take a 3.5 Service Pack 1 application
and run it on the V4.0 CLR. It needs a V2.0 CLR or reconfiguring with
a <supportedRuntimes/> tag in order to bend the application to run on
the V4.0 CLR and that bending might be something that you don’t want
to do.
From the link in bryanmac's answer (In-Process Side-by-Side):
This means that if an application is recompiled to run against the .NET Framework 4 runtime and still has dependent assemblies built against .NET 2.0, those dependents will load on the .NET 4 runtime as well.
That can mean, however, that there may be bugs due to being run on a different runtime.
If you have the source to SharpZipLib you could just rebuild it as .NET 4.0
I have winforms application. When I look at the references they are all .net 4 (same as the application) apart from one which says v2.0. I can run the app locally and use functionality from the .net components but as soon as I take the app to another machine it wont fire up. Apparently this hapens when references cant be found.
Im very confused as to why this would work locally. I have checked the GAC and only .net 2.0 versions exist for the referenced dlls.?..
What are the rules around rererencing dlls from older versions on .net?
It is perfectly fine to have the two versions of the framework running on the same machine. Are both .NET 2 and .NET 4 installed on the second machine you are testing on? I suspect that they are not.
Yes you can reference .Net 2.0 dlls from .Net 4.0 project.
You might be referencing only .Net 2.0 dlls but your target framework might be .Net 4.0, which might not be available on your other machine.
To correct this:
Open your project properties.
Set Target framework to .Net Framework 2.0 or 4.0.
If you set it to 4.0, you must have 4.0 installed on the machine you want it to run on.
The quickest way to see which versions are installed on a machine:
open VS command prompt and type clrver. (Ofcourse you'll need .Net SDK)
To see which framework your app uses type clrver
you can get for your application from task manager (in process tab, click View->select columns->check PID)
Starting .NET 4.0, your app can target multiple frameworks in different AppDomains in the same process.
Remember that the framework that your application is determined automatically, but you can override this default behaviours. One way to do this is what I described above.
Note that the GAC location has changed between .Net 2.0 and .Net 4.0. You most likely have both versions installed on your machine and you have looked at the 2.0 GAC.
The second machine most likely does not have 2.0 installed, hence it fails running.
I have a dll which is based on .net 3.5 -- it uses internally for example Linq, but the exposed API is straightforward, no fancy stuff. Since C# generics are resolved at compile time I assume that for calling party all it counts is API (all public parts).
However when I try to use this dll from net2.0 project I get info, that the dll cannot be referenced because the dll or one of its dependencies requires a later version of .net framework.
I can install any .net version I want on target computer (when entire app is installed), but I cannot change .net version for the project itself.
So: how to solve this? When adding a C dll to this project I had no such problems, so are C# dlls self-contained or not?
C# dlls need to have the .Net runtime to run as they are not compiled down to machine code. In this case the dll says it requires Net 3.5 so all your project will have to use 3.5 or higher.
To keep your project as Net 2.0 you would need to build another executable to contain the 3.5 DLL and communicate across separate processes.
The C DLL worked as it is compiled down to native code and does not require the .Net framework. (or at least not version higher than 2.0)
I've been using System.Core and the new System.Web.Extensions (for example) from 3.5 in an ASP.NET 2.0 app (using VS2005) for a while now with no problems. Similar to what Scott Hanselman blogged about here. So yes, it's possible.
.NET 3.5 still runs on the same CLR as .NET 2.0. So at runtime it's all the same. (Assuming you've tracked down any dependencies and copied those 3.5 DLLs to your bin folder as well.)
The only real limitation is what C# language features you can use at development time. Such as 'var', extension methods, or LINQ query syntax.
If you are using linq to objects, then you can use Linq Bridge:
http://www.albahari.com/nutshell/linqbridge.aspx
this is a Linq to objects implementation for .net 2.0.
You will still have to compile using vs2008 but you can compile with .net 2.0 as a target platform in that case.
(This is because the C# 3 compiler understands linq clauses even if you target .net 2.0, it will simply resolve the calls to linqbridge instead of the .NET 3.5 libraries in this case)
If you're using .NET 3.5 libraries then your application's requirements should be such that any consumer of it's API's should also be using .NET 3.5.
The only way you can bypass this is if you package all the dependencies of your application along with it. This means libraries your application uses which depend on the .NET 3.0 and 3.5 frameworks.
However, I'm not sure of the legality of ripping out chunks of the .NET frameworks and packaging them with an app. I'd read the EULA before doing anything like this. IMO, it's not worth the hassle; just install 3.5, ask your users to install 3.5 and be done with it or use only 2.0 features and libraries. At the very least, hacking around like this will only cause you more pain with deployment if there are framework updates in the future.
In either case, your app will work on .NET 2.0 as 3.0 and 3.5 are just extra libraries on top of the 2.0 runtime and libraries (as Craig mentioned) as long as all your dependencies are there.
C# DLLs are not self-contained. If your 3.5 DLL needs LINQ, it depends on system assemblies from the 3.5 (3.0 to be exact) framework, therefore the entire application depends on this version.
You could load the 3.5 assembly dynamically and use reflection to get access to the functions you need. This requires some overhead, of course.
Nothing pretty but there are ways to get the code happily working together (in the order of preference):
1) Upgrade both projects to 3.5
If I understand you correctly then your .net FW 2.0 Program will have dependency on 3.5 Library, which means for every functionality of the Program to work, it now requires FW 3.5. Since you state to have the code and authority to recompile the the Program AND install whatever FW on deployment, then you can upgrade it to 3.5. Sounds simple, but since you did not do this, then I guess you have good reasons (like other programs being higher up the call chain which you cannot upgrade to 3.5/recompile.)
2) Go around the FW2.0 compiler
Build the Program when referencing the 2.0 version of Library (or dummy, just providing the public API).
Build the 3.5 version of Library separately without Program (hence removing the need to reference the wrong FW assembly) and deploy the 3.5 version instead of the 2.0 version.
Since 2.0 and 3.5 use the same CLR runtime then fooling the compiler is enough. As long as the deployment maching has FW 3.5 installed, everything should be fine.
Note: everything is fine even if you have just .net 2.0 present on deployment machine and the user does not call .net 3.5 classes. If he does, there will be crash ;)
3) downgrade Library to 2.0
if you use only some classes of the .net FW then you could remain using the 2.0 compiler by adding those missing future assemblies to project. (this is the solution from Hanselman link shared by Craig). As already noted, you'll lose 3.5 compiler's syntactic sugar like vars.
Choose whichever suits your situation best.
Can I add a reference to System.Core.dll (.net 3.5) to a .net 2.0 application and use it
I am trying to use the TimeZoneInfo class which is available in .net 3.5 only, by referencing System.Core.dll
Alternatively, is their an alternate for TimeZoneInfo in .net 2.0
(or a customised class)
No you really should not. You must install 3.5 on the target machine or you will run into unpredictable behavior in the running program. The 3.5 framework including System.Core.dll depend on several bug fixes / features that were added to CLR 2.0 SP1 (this is a part of 3.5 framework). If you run against an unpatched CLR you will be essentially running untested code and will likely hit several bugs.
Scott Hanselman wrote a blog post describing how to run an early version of MVC on the 2.0 framework. He noted that the dependencies on System.Core will probably be OK as long as you are very careful not to call any routines that depend on CLR features specific to 3.0+ (for example, LINQtoSQL).
He rightly plastered the blog post with disclaimers that it is not supported, it very well might not work for you, but he got it to work and if you can, then yay for you.
I'm not sure if you can do this with System.Core.dll, but we have done this before with the Linq2Sql dlls for a .net 2.0 application. .net 3.5 uses the same version of the CLR with new assemblies built upon the .net 2.0 runtime. If you can get all of the dependencies, it might work. As I said, this worked for us with Linq2Sql dlls, but is not guaranteed for all scenarios. (For example, you probably wont be able to get WPF to run on Windows 2000, but you might be able to get Linq to Objects to work)
.net 3.5 runs on .net 2.0 runtime. So you should be able to use it... But referencing a single dll would lead to unexpected behaviour as you don't know all the dependencies system.core.dll have.... I would recommend not to do that...
You can do this, currently doing the same thing for a tool for work - also to utilize the TimeZoneInfo stuff. As long as thats all you're using you shouldn't run into any issues (at least I haven't).
However I'm not entirely sure of the legalities of bundling System.Core with your app. From what I know you're not allowed to.
I ended up utilizing the one from Mono for the tool that uses it.