Case Study: 1
Scenario 1
Background
You are developing a flight information consolidation service. The service retrieves flight information from a
number of sources and combines them into a single data set. The consolidated flight information is stored in a
SQL Server database. Customers can query and retrieve the data by using a REST API provided by the
service. The service also offers access to historical flight information. The historical flight information can be
filtered and queried in an ad hoc manner. The service runs on a Windows Azure Web Role. SSL is not used.
Business Requirements
A new data source for historical flight information is being developed by a contractor located on another
continent.
If a time zone is not specified, then it should be interpreted as Coordinated Universal Time (UTC).
When you upgrade a service from a staging deployment to a production deployment, the time that the service
is unavailable must be minimized.
The default port must be used for HTTP.
Technical Requirements
The existing sources of flight information and the mechanism of exchange are listed below.
Blue Yonder Airlines provides flight information in an XML file.
Consolidated Messenger provides flight information in a Microsoft Access database that is uploaded every 12
hours to the service using SFTP. The company uses port 22 for SFTP.
Margie’s Travel provides and consumes flight information using serialized ADO.NET DataSets. Data is
periodically synced between the service and Margie’s Travel.
Trey Research provides data from multiple sourcesserialized in proprietary binary formats. The datamust be
read by using .NET assemblies provided by Trey Research. The assemblies use a common set of
dependencies. The current version of the Trey Research assemblies is 1.2.0.0. All assemblies provided by
Trey Research are signed with a key pair contained in a file named Trey.snk, which Trey Research also
supplies.
The application specification requires that any third-party assemblies must have strong names.
Application Structure




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Errors occasionally occur when saving data using the FlightlnfoContext ADO.NET Entity Framework context.
Updates to the data are being lost when an error occurs. You need to ensure that data is still saved when an
error occurs by retrying the operation. No more than five retries should be performed. With which code
segment should you replace the body of the SaveChanges() method in the FlightInfoContext.cs file?

A.
Option A

B.
Option B

C.
Option C

D.
Option D

Explanation:
EntitySqlException : Represents errors that occur when parsing Entity SQL command text. This exceptionis
thrown when syntactic or semantic rules are violated.
SqlException : The exception that is thrown when SQL Server returns a warning or error. This class cannot be
inherited.
EntityCommandExecutionException : Represents errorsthat occur when the underlying storage provider could
not execute the specified command. This exception usually wraps a provider-specific exception.