C# Optional类代码示例

		private SelectFromQuery(bool? restriction, TopExpression top, Sequence<ColumnItem> columnItems, Optional<DestinationRowset> intoClause, FromClause fromClause, Optional<Predicate> whereClause, Optional<Sequence<Expression>> groupByClause, Optional<Predicate> havingClause,
		                        Optional<Sequence<OrderExpression>> orderList, ForClause forClause, RowsetCombineClause unionClause): base(restriction, top, columnItems, intoClause, whereClause, forClause, unionClause) {
			this.fromClause = fromClause;
			this.groupByClause = groupByClause.ToList();
			this.havingClause = havingClause;
			this.orderList = orderList.ToList();
		}

 internal ActiveContext(IActiveContextClr2Java clr2Java)
 {
     InstanceId = Guid.NewGuid().ToString("N");
     Clr2Java = clr2Java;
     _serializer = new AvroConfigurationSerializer();
     _parentId = Optional<string>.OfNullable(clr2Java.GetParentId());
 }

 // constructors
 /// <summary>
 /// Initializes a new instance of the <see cref="ServerSettings"/> class.
 /// </summary>
 /// <param name="heartbeatInterval">The heartbeat interval.</param>
 /// <param name="heartbeatTimeout">The heartbeat timeout.</param>
 public ServerSettings(
     Optional<TimeSpan> heartbeatInterval = default(Optional<TimeSpan>),
     Optional<TimeSpan> heartbeatTimeout = default(Optional<TimeSpan>))
 {
     _heartbeatInterval = Ensure.IsInfiniteOrGreaterThanOrEqualToZero(heartbeatInterval.WithDefault(DefaultHeartbeatInterval), "heartbeatInterval");
     _heartbeatTimeout = Ensure.IsInfiniteOrGreaterThanOrEqualToZero(heartbeatTimeout.WithDefault(DefaultHeartbeatTimeout), "heartbeatTimeout");
 }

 public void Deserialize(Deserializer deserializer)
 {
     this.Unknown0 = deserializer.ReadInt16();
     this.Unknown1 = deserializer.ReadVarint();
     this.Unknown2 = deserializer.ReadByte();
     this.Unknown3 = deserializer.ReadVarint();
     byte unknown4Length = deserializer.ReadByte();
     if (unknown4Length > 81)
     {
         throw new InvalidDataException();
     }
     Unknown4 = new byte[unknown4Length];
     for (int i = 0; i < Unknown4.Length; i++)
     {
         Unknown4[i] = deserializer.ReadByte();
     }
     this.Unknown5 = deserializer.ReadVector4();
     this.Unknown6 = deserializer.ReadVarint();
     if (deserializer.ReadBoolean())
     {
         this.Unknown7 = new Optional<Vector4>(deserializer.ReadVector4());
     }
     else
     {
         this.Unknown7 = null;
     }
     this.Unknown8 = deserializer.ReadByte();
     this.Unknown9 = deserializer.ReadByte();
     this.Unknown10 = deserializer.ReadByte();
     this.Unknown11 = deserializer.ReadInt16();
     this.Unknown12 = deserializer.ReadInt16();
     this.Unknown13 = deserializer.ReadInt16();
 }

		public CommonTableExpression(AliasName aliasName, Optional<Sequence<ColumnName>> columnNames, SelectQuery selectQuery) {
			Debug.Assert(aliasName != null);
			Debug.Assert(selectQuery != null);
			this.aliasName = aliasName;
			this.columnNames = columnNames.ToList();
			this.selectQuery = selectQuery;
		}

        /// <summary>
        /// Create a new ContextRuntime.
        /// </summary>
        /// <param name="serviceInjector"></param>
        /// <param name="contextConfiguration">the Configuration for this context.</param>
        /// <param name="parentContext"></param>
        public ContextRuntime(
                IInjector serviceInjector,
                IConfiguration contextConfiguration,
                Optional<ContextRuntime> parentContext)
        {
            ContextConfiguration config = contextConfiguration as ContextConfiguration;
            if (config == null)
            {
                var e = new ArgumentException("contextConfiguration is not of type ContextConfiguration");
                Org.Apache.REEF.Utilities.Diagnostics.Exceptions.Throw(e, LOGGER);
            }
            _contextLifeCycle = new ContextLifeCycle(config.Id);
            _serviceInjector = serviceInjector;
            _parentContext = parentContext;
            try
            {
                _contextInjector = serviceInjector.ForkInjector();
            }
            catch (Exception e)
            {
                Org.Apache.REEF.Utilities.Diagnostics.Exceptions.Caught(e, Level.Error, LOGGER);

                Optional<string> parentId = ParentContext.IsPresent() ?
                    Optional<string>.Of(ParentContext.Value.Id) :
                    Optional<string>.Empty();
                ContextClientCodeException ex = new ContextClientCodeException(ContextClientCodeException.GetId(contextConfiguration), parentId, "Unable to spawn context", e);
                
                Org.Apache.REEF.Utilities.Diagnostics.Exceptions.Throw(ex, LOGGER);
            }
            // Trigger the context start events on contextInjector.
            _contextLifeCycle.Start();
        }

        private CompletionRules With(
            Optional<bool> dismissIfEmpty = default(Optional<bool>),
            Optional<bool> dismissIfLastCharacterDeleted = default(Optional<bool>),
            Optional<ImmutableArray<char>> defaultCommitCharacters = default(Optional<ImmutableArray<char>>),
            Optional<EnterKeyRule> defaultEnterKeyRule = default(Optional<EnterKeyRule>))
        {
            var newDismissIfEmpty = dismissIfEmpty.HasValue ? dismissIfEmpty.Value : this.DismissIfEmpty;
            var newDismissIfLastCharacterDeleted = dismissIfLastCharacterDeleted.HasValue ? dismissIfLastCharacterDeleted.Value : this.DismissIfLastCharacterDeleted;
            var newDefaultCommitCharacters = defaultCommitCharacters.HasValue ? defaultCommitCharacters.Value : this.DefaultCommitCharacters;
            var newDefaultEnterKeyRule = defaultEnterKeyRule.HasValue ? defaultEnterKeyRule.Value : this.DefaultEnterKeyRule;

            if (newDismissIfEmpty == this.DismissIfEmpty
                && newDismissIfLastCharacterDeleted == this.DismissIfLastCharacterDeleted
                && newDefaultCommitCharacters == this.DefaultCommitCharacters
                && newDefaultEnterKeyRule == this.DefaultEnterKeyRule)
            {
                return this;
            }
            else
            {
                return Create(
                    newDismissIfEmpty,
                    newDismissIfLastCharacterDeleted,
                    newDefaultCommitCharacters,
                    newDefaultEnterKeyRule);
            }
        }

 internal ContextException(
     string contextId, Optional<string> parentId, string message, Exception inner) :
     base(message, inner)
 {
     _contextId = contextId;
     _parentId = parentId;
 }

        public void WhenOptionalIsSet()
        {
            var optional = new Optional<Int32>(123);

            Assert.IsTrue(optional.IsSet);
            Assert.AreEqual(optional.Value, 123);
        }

		public TableForeignKeyConstraint(ConstraintName constraintName, Sequence<ColumnName> columnNames, Qualified<SchemaName, TableName> refTableName, Optional<Sequence<ColumnName>> refColumnNames, Sequence<ForeignKeyAction> keyActions): base(constraintName) {
			Debug.Assert(refTableName != null);
			this.columnNames = columnNames.ToList();
			this.refTableName = refTableName;
			this.refColumnNames = refColumnNames.ToList();
			this.keyActions = keyActions.ToList();
		}

 static void CreateBinaryNuspec(
     string id, 
     string compiler, 
     IEnumerable<Targets.ItemDefinitionGroup> itemDefinitionGroupList,
     IEnumerable<Nuspec.File> fileList,
     IEnumerable<Nuspec.Dependency> dependencyList,
     Optional<string> name,
     IEnumerable<string> platformList)
 {
     var info = Config.CompilerMap[compiler];
     var description =
         id +
         ". Compiler: " +
         info.Name +
         ". Platforms: " +
         string.Join(", ", platformList) +
         ".";
     Nuspec.Create(
         id,
         id,
         Package.CompilerVersion(info),
         description,
         itemDefinitionGroupList,
         fileList,
         Enumerable.Empty<CompilationUnit>(),
         dependencyList,
         new[] { "binaries", compiler }.
             Concat(name.ToEnumerable()).
             Concat(platformList));
 }

        private static IInjector InjectServices(Optional<ServiceConfiguration> serviceConfig)
        {
            // TODO[JIRA REEF-217]: Use base injector for the Evaluator here instead.
            IInjector rootServiceInjector;

            if (serviceConfig.IsPresent())
            {
                rootServiceInjector = TangFactory.GetTang().NewInjector(serviceConfig.Value.TangConfig);
                InjectedServices services = null;
                try
                {
                    services = rootServiceInjector.GetInstance<InjectedServices>();
                }
                catch (Exception e)
                {
                    Utilities.Diagnostics.Exceptions.Caught(e, Level.Error, "Failed to instantiate service.", LOGGER);
                    InvalidOperationException ex = new InvalidOperationException(string.Format(CultureInfo.InvariantCulture, "Failed to inject service: encoutned error {1} with message [{0}] and stack trace:[{1}]", e, e.Message, e.StackTrace));
                    Utilities.Diagnostics.Exceptions.Throw(ex, LOGGER);
                }
                LOGGER.Log(Level.Info, string.Format(CultureInfo.InvariantCulture, "injected {0} service(s)", services.Services.Count));
            }
            else
            {
                rootServiceInjector = TangFactory.GetTang().NewInjector();
                LOGGER.Log(Level.Info, "no service provided for injection.");
            }
            
            return rootServiceInjector;
        }

 internal EvaluatorException(string evaluatorId, string message, string javaStackTrace)
     : base(message)
 {
     _evaluatorId = evaluatorId;
     _javaStackTrace = string.IsNullOrWhiteSpace(javaStackTrace)
         ? Optional<string>.Empty()
         : Optional<string>.Of(javaStackTrace);
 }

 // methods
 /// <summary>
 /// Returns a new ServerSettings instance with some settings changed.
 /// </summary>
 /// <param name="heartbeatInterval">The heartbeat interval.</param>
 /// <param name="heartbeatTimeout">The heartbeat timeout.</param>
 /// <returns>A new ServerSettings instance.</returns>
 public ServerSettings With(
     Optional<TimeSpan> heartbeatInterval = default(Optional<TimeSpan>),
     Optional<TimeSpan> heartbeatTimeout = default(Optional<TimeSpan>))
 {
     return new ServerSettings(
         heartbeatInterval: heartbeatInterval.WithDefault(_heartbeatInterval),
         heartbeatTimeout: heartbeatTimeout.WithDefault(_heartbeatTimeout));
 }

 /// <summary>
 /// Initializes a new instance of the <see cref="ResultCentricAggregateQueryTestResult"/> class.
 /// </summary>
 /// <param name="specification">The specification.</param>
 /// <param name="state">The state.</param>
 /// <param name="actualResult">The actual result.</param>
 /// <param name="actualException">The actual exception.</param>
 /// <param name="actualEvents">The actual events.</param>
 internal ResultCentricAggregateQueryTestResult(ResultCentricAggregateQueryTestSpecification specification, TestResultState state, Optional<object> actualResult, Optional<Exception> actualException, Optional<object[]> actualEvents)
 {
     _specification = specification;
     _state = state;
     _actualResult = actualResult;
     _actualException = actualException;
     _actualEvents = actualEvents;
 }