How to Resolve \'Unable to Retrieve Metadata\' Error in MVC4 with Entity Framework and MySQL?

Unable to Retrieve Metadata in MVC4 with Entity Framework and MySql

In an attempt to establish a data model for MVC4 using Entity Framework 4.4 with MySql, users may encounter an error related to metadata retrieval. This error message typically reads:

Unable to retrieve metadata for BTD.Data.Product using the same
DbCompiledModel to create context against different types of database
servers is not supported. Instead, create a separate DbCompiledModel
for each type of server being used.

Reasons for the Error

This issue can arise due to the inability of MVC4 Controller scaffolding to accurately recognize MySql connection strings when generating Entity Framework (EF) CRUD code.

Solution

To resolve the error, follow these steps:

1. Modify the Connection String:
   When generating EF CRUD code, change the connection string to point to a Microsoft SQL Server database (e.g., using System.Data.SqlClient).
2. Scaffold the Code:
   Add the controller and view scaffolding while using the modified connection string.
3. Revert the Connection String:
   Once the scaffolding is complete, revert the connection string to the original MySql configuration using MySql.Data.MySqlClient.

Additional Notes

• It has been observed that switching to a SQL Server database, scaffolding the code, and reverting to the MySql connection string may resolve the issue.
• Make sure your MySql version is supported and the appropriate .NET provider is installed.
• Review the database table structure and ensure it aligns with the EF data model.
• Consider using the [Code-First Migration approach](https://docs.microsoft.com/en-us/ef/core/get-started/using-mvc/migrations) with EF.

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