Why Does My Entity Framework Connection Fail with 'The underlying provider failed on Open,' and How Can I Fix It?

Troubleshooting "The underlying provider failed on Open" in Entity Framework

This error frequently arises when connecting to a database using Entity Framework and an .mdf file. A solution is to migrate to a database without an .mdf file.

Correcting the Connection String

For databases without .mdf files, verify your connection string's accuracy. A typical example:

<code class="language-xml"><connectionStrings>
  <add name="conString" 
       connectionString="metadata=res://*/conString.csdl|res://*/conString.ssdl|res://*/conString.msl;provider=System.Data.SqlClient;provider connection string='Data Source=.\SQL2008;Initial Catalog=NData;Integrated Security=True;Connect Timeout=30;User Instance=True;MultipleActiveResultSets=True'"
       providerName="System.Data.EntityClient" />
</connectionStrings></code>

Further Debugging Steps

If the connection string correction doesn't resolve the issue, investigate these possibilities:

• Integrated Security and Permissions: When using Integrated Security, confirm the IIS user possesses the necessary database access rights.
• Entity Framework Transactions and MSDTC: Avoid Entity Framework transactions spanning multiple database calls to prevent MSDTC-related problems.

Manual Transaction Handling

If transactions are essential, manage the connection explicitly within your code:

<code class="language-csharp">using (DatabaseEntities context = new DatabaseEntities())
{
    context.Connection.Open();
    // Execute database operations here
}</code>

This approach provides more control over the connection lifecycle and can help mitigate transaction-related errors.

The above is the detailed content of Why Does My Entity Framework Connection Fail with 'The underlying provider failed on Open,' and How Can I Fix It?. For more information, please follow other related articles on the PHP Chinese website!