System.NullReferenceException message in creating Entity Data Model in an MVC project

Andy Chiou 10

Hi everyone,
I created a localdb sql server file(School.mdf) in the App_Data folder in an MVC project using .Net Framework 4.8.  I then added a table(Student) with only two attributes for testing.  I tried to add new ADO .Net Entity Data Model into the Model folder and always received the System.NullReferenceException error.

I've not put any code into the the project yet and re-installed Visual Studio a couple of times and the error still exists.  This process worked before and for some reasons it keeps generating the same error.  I even re-installed my Windows but with no luck.  Please help and thanks in advance!  The environment and error code are as following:

Windows 11 Professional 22H2
Microsoft Visual Studio Enterprise 2022 (64 位元) - Current
Version 17.6.2
.Net Framework 4.8
Entity Framework 6

Microsoft.VisualStudio.TextTemplating5C5F7BACB8CEC88665887E68BA8F1FCD0354B98542C262332E3C8B13598380BCAB3FB85B22BC36C16486F51F7570BE5104F992A57C4BA4127540C07FC38CAD49.GeneratedTextTransformation.DynamicTextTransformation.get_GenerationEnvironment()
   at Microsoft.VisualStudio.TextTemplating5C5F7BACB8CEC88665887E68BA8F1FCD0354B98542C262332E3C8B13598380BCAB3FB85B22BC36C16486F51F7570BE5104F992A57C4BA4127540C07FC38CAD49.GeneratedTextTransformation.EntityFrameworkTemplateFileManager..ctor(Object textTransformation)
   at Microsoft.VisualStudio.TextTemplating5C5F7BACB8CEC88665887E68BA8F1FCD0354B98542C262332E3C8B13598380BCAB3FB85B22BC36C16486F51F7570BE5104F992A57C4BA4127540C07FC38CAD49.GeneratedTextTransformation.EntityFrameworkTemplateFileManager.VsEntityFrameworkTemplateFileManager..ctor(Object textTemplating)
   at Microsoft.VisualStudio.TextTemplating5C5F7BACB8CEC88665887E68BA8F1FCD0354B98542C262332E3C8B13598380BCAB3FB85B22BC36C16486F51F7570BE5104F992A57C4BA4127540C07FC38CAD49.GeneratedTextTransformation.EntityFrameworkTemplateFileManager.Create(Object textTransformation)
   at Microsoft.VisualStudio.TextTemplating5C5F7BACB8CEC88665887E68BA8F1FCD0354B98542C262332E3C8B13598380BCAB3FB85B22BC36C16486F51F7570BE5104F992A57C4BA4127540C07FC38CAD49.GeneratedTextTransformation.TransformText()	DBTest	C:\Users\schio\source\repos\DBTest\DBTest\Models\Model.tt	1

Hui Liu-MSFT 38,191 Reputation points Microsoft Vendor

2023-06-09T02:16:25.7+00:00

Hi,@ Andy Chiou. Welcome Microsoft Q&A.

The error you're experiencing seems to be related to the Entity Framework's code generation process for the ADO .NET Entity Data Model. This error can occur for various reasons, here are a few suggestions to troubleshoot and resolve the issue:

Check the connection string: Ensure that the connection string in your application's configuration file (Web.config or App.config) is correctly configured to point to the localdb SQL Server file (School.mdf). Make sure the connection string includes the correct provider, server, database name, and authentication details.

Disable third-party extensions: Temporarily disable any third-party extensions that might interfere with the Entity Framework template generation process. Go to "Extensions" > "Manage Extensions" in Visual Studio and disable any extensions that might be causing conflicts.

Clean and rebuild the solution: Go to the "Build" menu in Visual Studio and select "Clean Solution." Once the cleaning process is complete, select "Rebuild Solution." This will ensure that all project files are rebuilt and any cached template files are regenerated.

Delete the Entity Framework template files: In your project, locate the Model.tt file and its associated .edmx file (if it exists). Delete these files from your project. Then, right-click on the project, select "Add" > "New Item" > "Data" > "ADO.NET Entity Data Model" to add a new Entity Framework model to your project. This will generate fresh template files.

Repair or reinstall Entity Framework: Open the Visual Studio Installer and select the "Modify" option for your Visual Studio installation. In the Workloads tab, make sure that ".NET desktop development" and "ASP.NET and web development" are selected. Then, in the Individual components tab, locate "Entity Framework 6 tools" and ensure it is selected. Click on the "Modify" button to repair or reinstall the Entity Framework components.

Reset Visual Studio settings: In Visual Studio, go to the "Tools" menu > "Import and Export Settings" > "Reset all settings." Follow the prompts to reset the settings to their default values. This can help resolve any configuration issues that may be affecting the template generation process.
Andy Chiou 10 Reputation points

2023-06-09T07:43:03.0266667+00:00

Hi @Hui Liu-MSFT

Thanks for your reply. I've tried all your suggestions and still received the NullReferenceException error. I ended up with formatting my C and D drives, both containing applications, and re-installed the operating system and Visual Studio. I still received the error. It is very weird because it works on my other computer with same operating system and software configurations. Thanks anyway, and any suggestions are very appreciated.
延瑞刘 0 Reputation points

2023-06-10T02:56:18.6+00:00

I have the same question.
Hui Liu-MSFT 38,191 Reputation points Microsoft Vendor

2023-06-13T05:40:19.4566667+00:00

Hi,@ Andy Chiou. Did the project run successfully on this computer before the problem occurred? Are there some updates and changes? Are the systems and Visual Studio versions of your two computers the same? Is the Target framework and Platform target of your project the same on both computers? Is there anything else different?
Andy Chiou 10 Reputation points

2023-06-14T00:52:44.3333333+00:00

Thanks, @Hui Liu-MSFT , the configurations on both computers are the same. After a lot of digging, this workaround work for me.

https://www.codeproject.com/Tips/5362208/VS2022-ver-17-6-2-EntityFramework6-Broken

and the location of this file is

C:\Program Files\Microsoft Visual Studio\2022\Community\Common7\IDE\Extensions\

Microsoft\Entity Framework Tools\Templates\Includes\EF6.Utility.CS.ttinclude

Hope this helps.
Hui Liu-MSFT 38,191 Reputation points Microsoft Vendor

2023-06-14T01:51:20.11+00:00

Glad to hear your problem was solved.