I have a .net 4.0 project in which I'd like to reference .net 2.0 assemblies. As I understood from this article, .net 2.0 assemblies will be loaded in 4.0 run time and backward compatibility is not assured. Is there a way to force process side by side for this case and to load 2.0 runtime?
In process side-by-side versioning is only supported for code that runs independently without having to share data. In particular for native code that loads the CLR to execute managed code. It is a solution for the CLR versioning problem, once an unmanaged program like Explorer loads the CLR, say to support a shell extension written in .NET then the CLR version is selected by whatever version that extension asked for. Which works poorly if another extension then needs a later version of the CLR. .NET 4's side-by-side versioning feature solves that, each extension gets its own CLR. No sharing of data is required, these extensions don't know about each other.
Clearly this isn't a solution for what you are trying to do. Microsoft made a lot of effort to make .NET 4.0 as compatible as possible with previous .NET releases and loading .NET 2.0 assemblies is certainly well supported. Up to a point, they did use the opportunity to fix several old bugs whose fixes could be breaking to old code. Technically it is possible that your 2.0 code relied on the behavior of such a bug, it is however not very likely. You just need to re-test your code.
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We distribute a .NET 3.5 assembly to more parties to be referenced and used in different applications.
We are now intending to upgrade this assembly to .NET 4.6 so it will benefit of all performance and security improvements in this .NET version and not for using new .NET features.
But we don't want to break existing applications that are using it.
Some consumer applications might still be using .NET 3.5 so they won't be able to use it, so I was thinking how about having two projects targeting two .NET versions (3.5 and 4.6), but same code files.
What would you recommend for maintaining and distributing one assembly code base for both .NET 3.5 and .NET 4.6 version lines?
Later Edit: This question is not about referencing a .NET 4.6 assembly in .NET 3.5, it's about how can a .NET 4.6 application to use my assembly and benefit of the security and performance of .NET 4.6 while running it. The 3.5 apps should continue to use my 3.5 assembly.
Look into creating your own nuget repository and publish the libraries in each specific version of .net needed. (For one package can have varying .net versions as needed).
Once in your nuget repository they have their own version and can be updated either in lockstep or differently. That way the consumers can use the target version as needed for the target .net version.
See Hosting Your Own NuGet Feeds
There seem's to be an assumption that an identical code base compiled in .Net 4.6 will gain "performance and security". This isn't true. If the codebase is identical it will perform identically and the security will be the same.
Each iteration of .Net contains the previous one (it's actually a monolythic process that Microsoft are trying to move away from, hence projects such as Katana)
Each new version of the .NET Framework retains features from the
previous versions and adds new features.
source
Simply upgrading the framework will not magically make you code faster or more secure.
At a previous company we used to do as you are suggesting and ship a .NET 3.5 version (for users on XP) and a .NET 4.0+ (up to 4.5) version.
The way we did this was to have two separate solutions basically called the same and have each of the projects mirrored from the .NET 4.0 version into the 3.5 version. These were actual projects added to the solution.
For the files we simply linked the .NET 4.0 files directly into these projects, but we did have to manually create each folder so that the namespaces matched. For any code that was not supported by .NET 3.5 we had to create an actual file in the 3.5 solution and re-write entirely that feature so that it would compile with 3.5.
This was not fun and actually wasted a lot of development time simply looking after a legacy solution. In the end we migrated everything to .NET 4.5 and expressed to users that we were discontinuing support for the 3.5 version, for us there was not cost for the user to upgrade so it was up to them if they wished to upgrade hardware for new functionality.
In conclusion I would say if you don't need to I would recommend that you don't attempt to support both solutions, it will impact your development time and frustrate developers when they've written this nice feature using the concurrent functionality to then realize this isn't in .NET 3.5 (I know what this is like because I've had it happen).
We have an application with around 300+ components (dll's and a couple of exe's). Some of them target 4.0 framework, some use 2.0 framework, some are written in native C++ (unmanged), some uses C++/CLI and a couple of them are written in ManagedExtensions for C++.
Now our requirement is to migrate to .NET Framework 4.5.2.
So my question is:
Will it be OK if I just change the TargetFramework version on all the exe's to 4.5.2 with out changing the dll's TargetFramework version?
Does it guarantee that all my dll's are loaded and run in 4.5.2 runtime? (Included all the C++ dll's).
I have gone through multiple articles on internet and I could not find a concrete answer in the scenario where we have a mix of C#, managed c++ and unmanaged c++ dlls. Any help is appreciated.
Edit: Our team generate core libraries (sort of a framework) and few executables (targetted to 2.0 framework) which can be used by various other teams to meet their customer specific requirements. Some of the customers are not yet migrated from XP (Max .NET framework used in XP is 4.0). So along with newer OS's we still need to support clients using XP.
While 2.0 projects are generally upgradable to 4.5.x with no code changes, there are breaking-differences between .NET versions that you may run into. Given the scale and complexity of your project I must advise against blindly changing the TargetFramework property and hoping for the best.
While 4.0 executables can load 2.0 DLLs, it is not recommended because of the breaking-changes I described.
You will run into problems with the mixing of C++ code. I recommend you start by upgrading (or rather, rewriting) your "Managed Extensions for C++" code to C++/CLI (you might want to take advantage of C++11 and C++14 features present in VS2015 while you're at it).
I recommend upgrading each project individually and separately, working your way up the dependency-chain. It will help if you have (or will write) unit tests and integration tests for more critical parts of your system.
Migrating from 2.0 to 4.5.2 is just click click job, whereas no gaurantee thay it wont break anything. Recently I upgraded a webapplication to 4.5.2 and there were requestvalidation issue,3rd party tool broke and what not.
So one cannot say it will work seamlessly, you have to test it out to see if it works.
Now mixing 2.0 with 4.5.2 may cause chaos as you need to take into account consuming application too at the time of writing code.
I could not find the answer to this exact question but there are related ones.
We have BIG WinForms application that is compiled to use .NET 4. However, several of the DLL's that we call and all the 3rd party controls are compiled to use .NET 2. Obviously this works but are there any negative performance issues because of this scenario and if everything was using .NET 4 would it be faster.
I am not trying to micro optimize but if I can get a tiny/small boost by just recompiling what I have the source code for I am willing to make the effort if there is a gain.
In theory, there shouldn't be any significant impact on performance.
The compatibility goal for the .Net Framework is that applications and components from previous versions should work smoothly on the .Net Framework 4...
When a .NET 4.0 application loads a .NET 2.0 assembly, it gets loaded into the 4.0 runtime using a compatibility mode feature that helps to prevent breakages:
In-Proc SxS does not solve the compatibility problems faced by library developers. Any libraries directly loaded by an application--either via a direct reference or an Assembly.Load--will continue to load directly into the runtime and AppDomain of the application loading it. 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. Therefore, we still recommend testing your libraries against all version[s] of the framework you wish to support. This is one of the reasons we have continued to maintain our high level of backward compatibility.
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.