I have a core 3.1 console multi-targeting project where i want to access some EF6 data on .net 4.7.2 from core console through netstandard2.0

Hi,

I dont think I am using the multi-targeting correctly, and, Going from the console through netstandard2.0 is NOT multi-targeting. All I see from videos or forum post just show you how to set up multi-targeting, but then what. If you know of any links or videos that go beyond setting up a multi-targeting project, it would be VERY helpful.

This is my multi-targeting project:

My Mbsa .net 4.7.2 project:

My Mbsa Entity framework in .net 4.7.2 in web.config :
<section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false"/>

Here, I am calling the .netstandard method to return the EF member table data from .net 4.7.2 for member number 1.

when I run the core console app I get this error in my Mbsa .net 4.7.2.

This is the description
System.TypeInitializationException
HResult=0x80131534
Message=The type initializer for 'System.Data.Entity.Internal.AppConfig' threw an exception.
Source=EntityFramework
StackTrace:
at System.Data.Entity.Internal.AppConfig.get_DefaultInstance()
at System.Data.Entity.Internal.LazyInternalConnection..ctor(DbContext context, String nameOrConnectionString)
at System.Data.Entity.DbContext..ctor(String nameOrConnectionString)
at Mbsa.Models.MbsaDataEntities..ctor() in D:\MBSSys\Mbsa\Mbsa 2021\Models\MbsaDB.Context.cs:line 19
at Mbsa.Common.CommonRepo`1..ctor() in D:\MBSSys\Mbsa\Mbsa 2021\Common\CommonRepo.cs:line 24
at Mbsa.BL.MembersService..ctor() in D:\MBSSys\Mbsa\Mbsa 2021\BL\MembersService.cs:line 38
at MbsaDotNetStandard.MbsaUseFrameworkMethods.grabMbsaMember(Int32 mno) in D:\MBSSys\MbsaDotNetStandard\MbsaUseFrameworkMethods.cs:line 16
at MbsaMultiTargeting.Program.Main(String[] args) in D:\MBSSys\MbsaMultiTargeting\MbsaMultiTargeting\Program.cs:line 31

This exception was originally thrown at this call stack:
[External Code]

Inner Exception 1:
ConfigurationErrorsException: Configuration system failed to initialize

Inner Exception 2:
ConfigurationErrorsException: Unrecognized configuration section add. (D:\MBSSys\MbsaMultiTargeting\MbsaMultiTargeting\bin\Debug\netcoreapp3.1\MbsaMultiTargeting.dll.config line 3)

this is the problem. I have seen several posts about this from various forums but I dont know where to put what. It looks like I need a <section name> in my app.config.

this is my appsettings.json

This is what I SHOULD be focusing on "line 6 ":

Perhaps I need a new thread to clear what the focus should be on:
https://learn.microsoft.com/en-us/answers/questions/1114938/console-core-31-gives-this-error.html

thanks for any suggestions and advice

2 answers

Bruce (SqlWork.com) 67,916 Reputation points

2022-11-30T21:36:57.227+00:00

multi-target builds multiple versions of the application, one for each target. the core 3.1 target can not reference a 4.* library.

as there is no .netstandard 2.0 version of EF 6, all the library projects that use it must also be multi-target if you want to share between 4.* & core 3.1

note: EF 6 has a net45 and netstandard 2.1 version, which can be used for multi-targets
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iqworks Information Quality Works 296 Reputation points

2022-11-30T23:02:19.227+00:00

Hey Bruce, thanks as always. I understand (I think) why a blazor 3.1 project cannot access this .net4.7.2's EF 6. So now I am trying to access this EF 6 in .net4.7.2. I can access the 4.7.2 methods that return EF6 data in the .net4.7.2, but I am beginning to think I cannot invoke the EF6 processing from core 3.1?

Here is what I am seeing version wise in debugging .net4.7.2, netstandard2.0 and core console projects, watch :
When I start debugging from the core console, it says the version is this:

Then it gets into my .net4.7.2, but the version is:

The next debugging piece is STILL in .net4.7.2, its version is STILL .NETCoreApp,Version=v3.1

It looks like i need to get from 3.1 and 4.7.2 somehow?

or am i missing the point of what you are saying all together? IT SEEMS LIKE I AM SO CLOSE :-)

again, thanks Bruce for your time.

iqworks Information Quality Works 296 Reputation points

2022-12-01T00:02:07.177+00:00

multi-target builds multiple versions of the application, one for each target. the core 3.1 target can not reference a 4.* library.

this seems to say to me that core 3.1 is incompatible with 4.*? but i can access methods in 4.7.2, but are you saying EF6 on 4.7.2 cannot be accessed from 3.1core?

as there is no .netstandard 2.0 version of EF 6, all the library projects that use it must also be multi-target if you want to share between 4. & core 3.1*

What do you mean that .netstardard 2.0 is not compatible with EF 6 on 4.7.2? Because I can access the 4.7.2 programs and methods from 3.1, I have done this. So maybe i dont understand what you mean here?

note: EF 6 has a net45 and netstandard 2.1 version, which can be used for multi-targets

does this mean i need to use netstandard 2.1 with net45 to access EF6 on 4.7.2?

thanks as always for your time

Zhi Lv - MSFT 32,546 Reputation points Microsoft Vendor

2022-12-02T09:43:25.537+00:00

Hi @iqworks Information Quality Works ,

Check the official document: ASP.NET Core 3.x or later can only target .NET Core. Generally, ASP.NET Core is composed of .NET Standard libraries. Libraries written with .NET Standard 2.0 run on any .NET platform that implements .NET Standard 2.0.

So, in your asp.net core 3.1 application, you can't target the 4.X Framework.

Since, you want to use EF 6. It supports .NET Standard 2.1, which is currently supported by .NET Core 3.0 or later and it also supports .NET 4.0 and 4.5 or later. But it does not support .Net Standard 2.0. You can check the source code.

Bruce (SqlWork.com) 67,916 Reputation points

2022-12-02T16:46:36.483+00:00

the issue is that there is not a .netstandard 2.0 package for EF 6. this means you can not build a .netstandard 2.0 class lib that uses EF6. to share a class lib that references EF6 requires you build a multi-target class library.

the easiest way is to create a .net 6 class lib. then add the multi-target v4.7.2 (or whatever version you want).

https://learn.microsoft.com/en-us/visualstudio/msbuild/msbuild-multitargeting-overview?view=vs-2022

note: because of the multi-target you will be restricted to c# 7.3 syntax. all packages you use must have .netstandard 2.0 support, or both core and .net 4.* support. I have had to use conditional builds include the correct nuget packages sometimes.

iqworks Information Quality Works 296 Reputation points

2022-12-02T21:22:01.423+00:00

Hi Bruce & ZhiLv-MSFT, thanks for getting back and for giving me that link.

I found a good video about referencing :
https://www.youtube.com/watch?v=fMBQ0C17nuY
he even mentions how its hard to find information about a particular configuration you are trying to work with right in the beginning of the video. He also spoke of trying to google stackoverflow or others for the same config. Its interesting..

You are right about .netstandard2.1 not working with .net 4.7.2.
I am trying to access the EF 6.4.4 (sorry I may have misled you about the objects that are in play here) on my .net 4.7.2 from my core console project, but, through .netstandard2.0. , and then returning that data back to my core console 3.1 project from .netstandard2.0 to display on the console screen.

****> The current error is (as in one of the images from my previous post)

Inner Exception 1:
ConfigurationErrorsException: Configuration system failed to initialize
Inner Exception 2:
ConfigurationErrorsException: Unrecognized configuration section add. (D:\MBSSys\MbsaMultiTargeting\MbsaMultiTargeting\bin\Debug\net472\MbsaMultiTargeting.exe.Config line 6)****

thanks again to both of you two for the really helpful info. Will continue to keep this post up to date for others as well.

iqworks Information Quality Works 296 Reputation points

2022-12-03T21:18:47.47+00:00

Hi Bruce & ZhiLv. The error is telling me exactly where I should look. Here is the error again :
> The current error is (as in one of the images from my previous post)
Inner Exception 1:
ConfigurationErrorsException: Configuration system failed to initialize
Inner Exception 2:
ConfigurationErrorsException: Unrecognized configuration section add. (D:\MBSSys\MbsaMultiTargeting\MbsaMultiTargeting\bin\Debug\net472\MbsaMultiTargeting.exe.Config line 6)

it shows me where to look, I needed to look here :
MbsaMultiTargeting.exe.Config.
Never knew this actually existed, its not in the VS objects.

Its the best clue so far!! I thought I would share with you because maybe you can give some advice. I see all kinds of post with different configurations of a config file. They are talking about different project types. My project type is a core console 3.1.

I think I need to start another thread because This error and clue needs its own thread.

iqworks Information Quality Works 296 Reputation points

2022-12-09T00:43:32.457+00:00

Hi Yiyi, what i am trying use core 3.1 to access my .net4.7.2 EF6, THROUGH .netstandard.
Bruce was correct, you cannot access .net4.7.2 from core 3.1. But I found the actual reason.
Core 3.1 puts its connection string in appsettings.json. net4.7.2 cannot read this appsettings.json, it only reads its web.consig file. One solution is to pass the connection string from core 3.1 through .netstandard to .net7.7.2. This was ONE suggestion.

But, for others that are looking into this issue. Do a google search with "core 3.1 console .nt472 Message=No connection string named could be found in the application config file. Source=EntityFramework". Here you will find MANY links of people suggesting there reasoning and, many different ways to get around this.

But thanks for any further input from Bruce and ZhiLv for your suggestions and advice.

iqworks Information Quality Works 296 Reputation points

2022-12-09T19:59:41.533+00:00

Hi Yiyi, what i am trying to do is to use core 3.1 to access my .net4.7.2 EF6, THROUGH .netstandard.

Bruce was correct, you cannot access .net4.7.2 from core 3.1. But I found the actual reason pertaining to my particular issue.
Core 3.1 puts its connection string in appsettings.json. net4.7.2 cannot read this appsettings.json, it only reads its web.consig file. One solution is to pass the connection string as a parm or something like a session variable and send it from core 3.1 through .netstandard to .net7.7.2. This was ONE suggestion.

But, for others that are looking into this issue. Do a google search with "core 3.1 console .nt472 Message=No connection string named could be found in the application config file. Source=EntityFramework". Here you will find MANY links of people explaining this issue and, the many different ways each link showing how to get around this.

Thank you guys for your help and enlighting information.
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iqworks Information Quality Works 296 Reputation points

2022-12-09T20:05:05.627+00:00

Hi Bruce & ZhiLv-MSFT
Bruce was correct, you cannot access .net4.7.2 from core 3.1. But I found the actual reason pertaining to my particular issue.
Core 3.1 puts its connection string in appsettings.json. net4.7.2 cannot read this appsettings.json, it only reads its web.consig file. One solution is to pass the connection string as a parm or something like a session variable and send it from core 3.1 through .netstandard to .net7.7.2. This was ONE suggestion.

But, for others that are looking into this issue. Do a google search with "core 3.1 console .nt472 Message=No connection string named could be found in the application config file. Source=EntityFramework". Here you will find MANY links of people explaining this issue and, the many different ways each link showing how to get around this.

Thank you guys for your help and enlighting information.
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I have a core 3.1 console multi-targeting project where i want to access some EF6 data on .net 4.7.2 from core console through netstandard2.0

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