What additional configuration is necessary to reference a NET 2 0 mixed mode assembly in a NET 4 0 project

Question

I have a project in which I d like to use some of the  NET 4 0 features but a core requirement is that I can use the System Data SQLite framework which is compiled against 2 X  I see mention of this being possible such as the accepted answer here but I don t see how to actually achieve this   When I just try and run my 4 0 project while referencing the 2 X assembly I get      Mixed mode assembly is built against version  v2 0 50727  of the runtime    and cannot be loaded in the 4 0 runtime without additional    configuration information    What  additional configuration  is necessary

User · Answer

Using 2 0 and 4 0 assemblies together isn t quite straight forward   The ORDER of the supported framework declarations in app config actually have an effect on the exception of mixed mode being thrown  If you flip the declaration order you will get mixed mode error  This is the purpose of this answer   So if you get the error in a Windows Forms app    try this  mostly Windows Forms apps      lt startup useLegacyV2RuntimeActivationPolicy  true  gt       lt supportedRuntime version  v4 0  sku   NETFramework Version v4 0 Profile Client   gt       lt supportedRuntime version  v2 0 50727  gt  lt  supportedRuntime gt     lt  startup gt    Or if the project is not Windows Form  In a Web project add this to web config file      lt startup useLegacyV2RuntimeActivationPolicy  true  gt       lt supportedRuntime version  v4 0  sku   NETFramework Version v4 0   gt       lt supportedRuntime version  v2 0 50727  gt  lt  supportedRuntime gt     lt  startup gt

User · Answer

I was experiencing this same error  and spent forever adding the suggested startup statements to various config files in my solution  attempting to isolate the framework mismatch   Nothing worked   I also added startup information to my XML schemas   That didn t help either   Looking at the actual file that was causing the problem  which would only say it was  moved or deleted   revealed it was actually the License Compiler  LC    Deleting the offending licenses licx file seems to have fixed the problem

User · Answer

If your are working in a web service and the v2 0 assembly is a dependency that has been loaded by WcfSvcHost exe then you must include    lt startup useLegacyV2RuntimeActivationPolicy  true  gt       lt supportedRuntime version  v4 0    gt   lt  startup gt    in    Microsoft Visual Studio 10 0 Common7 IDE  WcfSvcHost exe config file  This way  Visual Studio will be able to send the right information through the loader at runtime

User · Answer

Depending on what version of the framework you re targeting  you may want to look here to get the correct string  http   msdn microsoft com en-us library ee517334 aspx I wasted hours trying to figure out why my release targeting  Net 4 0 client required the full version  I used this in the end   lt startup useLegacyV2RuntimeActivationPolicy  quot true quot  gt     lt supportedRuntime version  quot v4 0 30319 quot                  sku  quot  NETFramework Version v4 0 Profile Client quot    gt   lt  startup gt

User · Answer

I ran into this issue when we changed to Visual Studio 2015  None of the above answers worked for us  In the end we got it working by adding the following config file to ALL sgen exe executables on the machine   lt  xml version   1 0   gt       lt configuration gt           lt startup useLegacyV2RuntimeActivationPolicy  true  gt               lt supportedRuntime version  v4 0    gt           lt  startup gt       lt  configuration gt    Particularly in this location  even when we were targeting  NET 4 0   C  Program Files  x86  Microsoft SDKs Windows v10 0A bin NETFX 4 6 Tools

User · Answer

Was able to solve the issue by adding  startup  element with  useLegacyV2RuntimeActivationPolicy  attribute set     lt startup useLegacyV2RuntimeActivationPolicy  true  gt       lt supportedRuntime version  v4 0  sku   NETFramework Version v4 0   gt       lt supportedRuntime version  v2 0 50727   gt   lt  startup gt    But had to place it as the first child element of configuration tag in App config for it to take effect    lt  xml version  1 0   gt     lt configuration gt       lt startup useLegacyV2RuntimeActivationPolicy  true  gt         lt supportedRuntime version  v4 0  sku   NETFramework Version v4 0   gt         lt supportedRuntime version  v2 0 50727   gt       lt  startup gt

User · Answer

I had this problem when upgrading to Visual Studio 2015 and none of the solutions posted here made any difference  although the config is right the location for the change is not  I fixed this issue by adding this configuration    lt startup useLegacyV2RuntimeActivationPolicy  true  gt   lt  startup gt    To  C  Program Files  x86  Microsoft Visual Studio 14 0 Common7 IDE CommonExtensions Microsoft TestWindow TE ProcessHost Managed exe config  Then restarted Visual Studio

User · Answer

I Use   lt startup useLegacyV2RuntimeActivationPolicy  true  gt       lt supportedRuntime version  v4 0   gt       lt supportedRuntime version  v2 0 50727   gt   lt  startup gt    It s works but just before de  lt  configuration gt  tag otherwise the startup tag doesn t work properly

User · Answer

In order to use a CLR 2 0 mixed mode assembly  you need to modify your App Config file to include    lt  xml version  quot 1 0 quot   gt  lt configuration gt    lt startup useLegacyV2RuntimeActivationPolicy  quot true quot  gt      lt supportedRuntime version  quot v4 0 quot  sku  quot  NETFramework Version v4 0 quot   gt    lt  startup gt  lt  configuration gt   The key is the useLegacyV2RuntimeActivationPolicy flag   This causes the CLR to use the latest version  4 0  to load your mixed mode assembly   Without this  it will not work   Note that this only matters for mixed mode  C   CLI  assemblies   You can load all managed CLR 2 assemblies without specifying this in app config

User · Answer

Once you set the app config file  visual studio will generate a copy in the bin folder named App exe config  Copy this to the application directory during deployment  Sounds obvious but surprisingly a lot of people miss this step  WinForms developers are not used to config files

User · Answer

I was facing a similar issue while migrating some code from VS 2008 to VS 2010 Making changes to the App config file resolved the issue for me    lt configuration gt   lt startup useLegacyV2RuntimeActivationPolicy  true  gt   lt supportedRuntime version  v4 0 30319           sku   NETFramework Version v4 0 Profile Client    gt   lt  startup gt   lt  configuration gt

User · Answer

The above didnt work for me  I am working on a web app  - but this did     Edit the sgen exe config file in the folder  I had to create one first   C  Program Files  x86  Microsoft SDKs Windows v8 0A bin NETFX 4 0 Tools  There is also one in v7 0 folder  but I didnt need to change that one  I am using VS2012   The conents of the XML should look like this  same in previous answers    lt  xml version   1 0   gt   lt configuration gt       lt startup useLegacyV2RuntimeActivationPolicy  true  gt           lt requiredRuntime safemode  true  imageVersion  v4 0 30319  version  v4 0 30319   gt       lt  startup gt   lt  configuration gt

User · Answer

Add following at this location C  Program Files  x86  Microsoft SDKs Windows v7 0A Bin NETFX 4 0 Tools x64 FileName  sgen exe config If you dont find this file  create and add one    x000D   x000D    lt  xml version   1 0   gt  x000D   x000D   lt configuration gt  x000D    lt runtime gt          x000D           lt generatePublisherEvidence enabled  false   gt      x000D       lt  runtime gt  x000D   x000D       lt startup useLegacyV2RuntimeActivationPolicy  true  gt  x000D   x000D                   lt supportedRuntime version  v4 0    gt  x000D   x000D       lt  startup gt      x000D   x000D   lt  configuration gt  x000D   x000D   x000D    Doing this resolved the issue

User · Answer

This forum post on the  NET Framework Developer Center   It might provide some insight    Add to the app s config file     lt configuration gt     lt startup useLegacyV2RuntimeActivationPolicy  true  gt       lt supportedRuntime version  v4 0   gt     lt  startup gt   lt  configuration gt

User · Answer

I found a way around this after 3-4 hours of googling  I have added the following    lt startup selegacyv2runtimeactivationpolicy  true  gt     lt supportedruntime version  v4 0  sku   NETFramework Version v4 0 Profile Client    gt   lt  startup gt    If this doesn t solve your problem then--  In the Project References Right Click on DLL where you getting error --  Select Properties--  Check the Run-time Version --  If it is v2 0 50727 then we know the problem   The Problem is  - you are having 2 0 Version of respective DLL   Solution is - You can delete the respective DLL from the Project references and then download the latest version of DLL s from the corresponding website and add the reference of the latest version DLL reference then it will work

User · Answer

Also i had this issue with the class library  If any one have the issue with the class library added to your main application  Just add   lt startup useLegacyV2RuntimeActivationPolicy  true  gt    to you main application which would then be picked by the class library

User · Answer

I used this config    lt startup useLegacyV2RuntimeActivationPolicy  true  gt       lt supportedRuntime version  v2 0   gt       lt supportedRuntime version  v4 0   gt   lt  startup gt    Worked for me

[c#] What 'additional configuration' is necessary to reference a .NET 2.0 mixed mode assembly in a .NET 4.0 project?

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