EntityException: The underlying provider failed on Open

 Issue: When you try to launch a local ASP.NET MVC web application on Azure you receive following error:

[EntityException: The underlying provider failed on Open.]
   …http://System.Data.Entity.Core.EntityClient.EntityConnection.Open () +324
   http://ASP.NET _MVC5_Bootstrap_3._3._4_LESS1.Controllers.farmersController.Index(String sortOrder, String searchString, Nullable`1 page, String currentFilter) +99
SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 52 - Unable to locate a Local Database Runtime installation. Verify that SQL Server Express is properly installed and that the Local Database Runtime feature is enabled.)

Cause: Most probably this issue occurs when web application is attempts to reference a local database, which it wouldn't find which is causing that error.

Solution: To resolve above issue follow these steps:
1. Go to Azure Portal > Web App > settings > Application Settings.
2. Under connection strings verify that the connection string was correctly deployed.