How to Fix \'Unable to retrieve metadata\' Error when using Entity Framework and MySql in MVC4?

Unable to Retrieve Metadata in MVC4 with Entity Framework and MySql

The error "Unable to retrieve metadata for [model class]" often arises when using Entity Framework with MySql in MVC4. This issue stems from a limitation in MVC4 controller scaffolding, which does not correctly identify MySql connection strings.

To resolve this issue, follow these steps:

During Controller Scaffolding Only:

1. Change the connection string in web.config to use the following syntax:

<connectionStrings>
    <add name="BTDContext" connectionString="Data Source=host_name;Database=database_name;uid=user_id;pwd=password;" providerName="System.Data.SqlClient" />
</connectionStrings>

2. Generate the scaffolding for your controller and views.

After Scaffolding:

3. Revert the connection string back to the original MySql connection string:

<connectionStrings>
    <add name="BTDContext" connectionString="Data Source=host_name;Database=database_name;uid=user_id;pwd=password;" providerName="MySql.Data.MySqlClient" />
</connectionStrings>

This workaround allows MVC4 scaffolding to properly generate the necessary metadata for your model, while still allowing your application to connect to the MySql database at runtime.

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