System.Data.SqlClient.SqlException (0x80131904) when executing update-database in the package manager

When I am doing an update-database in the package manager in visual studio I am getting the error. Can someone help me ?

System.Data.SqlClient.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: 26 - Error Locating Server/Instance Specified)atSystem.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, DbConnectionPool pool, String accessToken, Boolean applyTransientFaultHandling, SqlAuthenticationProviderManager sqlAuthProviderManager) at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions) ClientConnectionId:00000000-0000-0000-0000-000000000000 Error Number:-1,State:0,Class:20 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: 26 - Error Locating Server/Instance Specified)

Below you find the connection string from the web.config:

<connectionStrings>
    <add name="StadsAppServicesContext" 
         connectionString="Data Source=(localdb)\MSSQLLocalDB; Initial Catalog=StadsAppServicesContext-20181027170930; Integrated Security=True; MultipleActiveResultSets=True; AttachDbFilename=|DataDirectory|StadsAppServicesContext-20181027170930.mdf"
         providerName="System.Data.SqlClient" />
</connectionStrings>