System.InvalidOperationException: The ConnectionString property has not been initialized.
at System.Data.SqlClient.SqlConnection.PermissionDemand()
at System.Data.SqlClient.SqlConnectionFactory.PermissionDemand(DbConnection outerConnection)
at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)
at System.Data.SqlClient.SqlConnection.Open()
at ASP.cities_aspx.Page_Load(Object sender, EventArgs e)