C# Expressions.NewExpression类代码示例

        protected override Expression VisitNew(NewExpression node)
        {
            var originalConstructorParameters = node.Arguments.Select(x => x.Type).ToList();
            var genericType = node.Constructor.DeclaringType.GetGenericTypeDefinition();
            var genericTypeParameters = genericType.GetTypeInfo().GenericTypeArguments.ToList();
            var originalGenericArgs = node.Constructor.DeclaringType.GetTypeInfo().GenericTypeArguments.ToList();

            if (genericTypeParameters.Count != _newGenericArgs.Length)
            {
                throw new InvalidOperationException("Wrong number of generic argument values specified. This type requires " + genericTypeParameters.Count + " generic type arguments");
            }
            for (int i = 0; i < _newGenericArgs.Length; i++)
            {
                var constraints = genericTypeParameters[i].GetTypeInfo().GetGenericParameterConstraints().ToList();
                foreach (var constraint in constraints)
                {
                    if (!constraint.GetTypeInfo().IsAssignableFrom(_newGenericArgs[i].GetTypeInfo()))
                    {
                        throw new InvalidOperationException("Generic type parameter " + i + " is constrained to type " + constraint + ". The supplied type " + _newGenericArgs[i] + " does not meet this constraint");
                    }
                }
            }

            result = genericType.MakeGenericType(_newGenericArgs.ToArray()).GetTypeInfo().DeclaredConstructors.Where(x => x == node.Constructor).Single();
            throw new VisitStoppedException();
        }

 protected ListInitExpression UpdateListInit(ListInitExpression init, NewExpression nex, IEnumerable<ElementInit> initializers)
 {
     if (nex != init.NewExpression || initializers != init.Initializers) {
         return Expression.ListInit(nex, initializers);
     }
     return init;
 }

        /// <summary>
        /// Visits new object expression like new DateTime().
        /// </summary>
        /// <param name="node">Node to visit.</param>
        /// <returns>Original node.</returns>
        protected override Expression VisitNew(NewExpression node)
        {
            var newObject = node.Constructor.Invoke(node.Arguments.Select(a => ((ConstantExpression)a).Value).ToArray());
            PrintConstant(newObject);

            return node;
        }

        protected override Expression VisitNew(NewExpression newExpression)
        {
            Check.NotNull(newExpression, nameof(newExpression));

            var newNewExpression = base.VisitNew(newExpression);

            var selectExpression = QueryModelVisitor.TryGetQuery(_querySource);

            if (selectExpression != null)
            {
                for (var i = 0; i < newExpression.Arguments.Count; i++)
                {
                    var aliasExpression
                        = selectExpression.Projection
                            .OfType<AliasExpression>()
                            .SingleOrDefault(ae => ae.SourceExpression == newExpression.Arguments[i]);

                    if (aliasExpression != null)
                    {
                        aliasExpression.SourceMember
                            = newExpression.Members?[i]
                              ?? (newExpression.Arguments[i] as MemberExpression)?.Member;
                    }
                }
            }

            return newNewExpression;
        }

 /// <summary>
 /// Constructor with an <see cref="NewExpression"/> and an <see cref="ExpressionConverter"/>.
 /// </summary>
 /// <param name="expression">The original, not serializable <see cref="Expression"/>.</param>
 /// <param name="expConverter">The <see cref="ExpressionConverter"/> to convert contained <see cref="Expression">Expressions</see>.</param>
 public SerializableNewExpression(NewExpression expression, ExpressionConverter expConverter)
     : base(expression, expConverter)
 {
     Arguments = expression.Arguments.MakeSerializableCollection<SerializableExpression>(expConverter);
     Members = InterLinqTypeSystem.Instance.GetCollectionOf<InterLinqMemberInfo>(expression.Members);
     Constructor = InterLinqTypeSystem.Instance.GetInterLinqVersionOf<InterLinqConstructorInfo>(expression.Constructor);
 }

        protected override Expression VisitNew(NewExpression node)
        {
            // specialize for DateTime
            if (FormatIfExprIsDateTime(node)) return node;

            // promising type initializer(goto:VisitMemberInit)
            if (!node.Type.IsAnonymousType()) return node;

            var indent = BuildIndent();
            var innerTranslator = new BigQueryTranslateVisitor(depth, indentSize);

            var merge = node.Members.Zip(node.Arguments, (x, y) =>
            {
                var rightValue = innerTranslator.VisitAndClearBuffer(y);

                if (x.Name == rightValue.Trim('[', ']')) return "[" + x.Name + "]";

                return rightValue + " AS " + "[" + x.Name + "]";
            });

            var command = string.Join("," + Environment.NewLine,
                merge.Select(x => indent + x));

            sb.Append(command);

            return node;
        }

        public LetSelectExpressionNode(MethodCallExpressionParseInfo parseInfo, LambdaExpression selector)
            : base(Utils.CheckNotNull("parseInfo", parseInfo), Utils.CheckNotNull("selector", selector))
        {
            // Heuristically detect "let" constructs
            // Assume a Select call is a "let" construct if its selector looks like this: <x> => new { <x> = <x>, <y> = ... }
            var selectorBody = selector.Body as NewExpression;
            if (selectorBody != null
                && selectorBody.Arguments.Count == 2
                && selectorBody.Arguments[0] == selector.Parameters[0]
                //&& selectorBody.Constructor.DeclaringType.IsDefined(typeof(CompilerGeneratedAttribute), false)
                && selectorBody.Members != null
                && selectorBody.Members.Count == 2)
            {
                _letConstruction = selectorBody;

                _resolvedAdaptedSelector = new ResolvedExpressionCache<Expression>(this);
                _resolvedLetExpression = new ResolvedExpressionCache<Expression>(this);
            }
            else
            {
                _letConstruction = null;

                _resolvedAdaptedSelector = null;
                _resolvedLetExpression = null;
            }
        }

        static void Main(string[] args)
        {

            //int maxCount = 40000;
            //List<HotSpotEntities> collection = new List<HotSpotEntities>();
            //for (int i = 0; i < maxCount; i++)
            //{
            //    Console.WriteLine(string.Format("成功创建连接对象{0}", i));
            //    var db = new HotSpotEntities();
            //    db.Connection.Open();
            //    collection.Add(db);
            //}

            Expression<Func<int, bool>> exp1 = x => x > 5;
            Expression<Func<int, bool>> exp2 = x => x < 10;

            ParameterExpression y = Expression.Parameter(typeof(int), "y");
            var newExp = new NewExpression(y);
            var newexp1 = newExp.Replace(exp1.Body);
            var newexp2 = newExp.Replace(exp2.Body);
            var newbody = Expression.And(newexp1, newexp2);

            Expression<Func<int, bool>> res = Expression.Lambda<Func<int, bool>>(newbody, y);
            //将表达式树描述的lambda表达式编译为可执行代码，并生成表示该lambda表达式的委托
            Func<int, bool> del = res.Compile();
            Console.WriteLine(del(7));
            Console.ReadLine();

        }

 public ListInitExpression Update(NewExpression newExpression, IEnumerable<ElementInit> initializers)
 {
   Contract.Requires(newExpression != null);
   Contract.Requires(initializers != null);
   Contract.Ensures(Contract.Result<ListInitExpression>() != null);
   return default(ListInitExpression);
 }

 protected MemberInitExpression UpdateMemberInit(MemberInitExpression init, NewExpression nex, IEnumerable<MemberBinding> bindings)
 {
     if (nex != init.NewExpression || bindings != init.Bindings) {
         return Expression.MemberInit(nex, bindings);
     }
     return init;
 }

 public MemberInitExpression Update(NewExpression newExpression, IEnumerable<MemberBinding> bindings)
 {
   Contract.Requires(newExpression != null);
   Contract.Requires(bindings != null);
   Contract.Ensures(Contract.Result<MemberInitExpression>() != null);
   return default(MemberInitExpression);
 }

        private object InvokeConstructor(NewExpression expression, object[] args, out int argumentCount)
        {
            object valueToSet;
            int nestedArgumentCount;

            argumentCount = 0;
            ArrayList argList = new ArrayList();

            int i = 0;
            foreach (var arg in expression.Arguments)
            {
                switch (arg.NodeType)
                {
                    case ExpressionType.New:
                        valueToSet = InvokeConstructor((NewExpression)arg, args.Skip(i).ToArray(), out nestedArgumentCount);
                        i += nestedArgumentCount;
                        break;

                    case ExpressionType.MemberInit:
                        valueToSet = InvokeMemberInitExpression((MemberInitExpression)arg,
                            args.Skip(i).ToArray(), out nestedArgumentCount);
                        i += nestedArgumentCount;
                        break;

                    default:
                        valueToSet = LinqUtil.ChangeType(args[i], arg.Type);
                        i++;
                        break;
                }
                argList.Add(valueToSet);
            }

            argumentCount = i;
            return expression.Constructor.Invoke(argList.ToArray());
        }

        protected override Expression VisitNew(NewExpression node)
        {
            var newNode = (NewExpression)base.VisitNew(node);
            if (newNode.Type.IsGenericType
                && newNode.Type.GetGenericTypeDefinition() == typeof(HashSet<>)
                && newNode.Arguments.Count == 1
                && newNode.Arguments[0] is AccumulatorExpression
                && ((AccumulatorExpression)newNode.Arguments[0]).AccumulatorType == AccumulatorType.Push)
            {
                Guid correlationId = Guid.Empty;
                if (_groupMap == null || TryGetCorrelatedGroup(node.Arguments[0], out correlationId))
                {
                    Expression accumulator = new AccumulatorExpression(
                        newNode.Type,
                        AccumulatorType.AddToSet,
                        ((AccumulatorExpression)newNode.Arguments[0]).Argument);

                    if (_groupMap != null)
                    {
                        accumulator = new CorrelatedAccumulatorExpression(
                            correlationId,
                            (AccumulatorExpression)accumulator);
                    }

                    return accumulator;
                }
            }

            return newNode;
        }

        protected override Expression VisitNew(NewExpression nex)
        {
            nex = (NewExpression)base.VisitNew(nex);

            var instance = (Expression)null;
            var method = (MethodBase)null;
            return Matcher
                .For(nex)
                    .Type(t => t.IsSubclassOf<Delegate>())
                    .Argument(0).AssignTo(out instance)

                .For(nex)
                    .Argument(1).As<AddressOfExpression>()
                        .Do(x => method = x.Method)

                .IfMatched<Expression>(
                    () => Expression.Call(null, CreateDelegateMethodInfo, new[] {
                        Expression.Constant(nex.Type),
                        instance,
                        Expression.Constant(method),
                        Expression.Constant(true)
                    }).Convert(nex.Type),
                    nex
                );
        }

        protected override Expression VisitNew(NewExpression node)
        {
            var args = node.Arguments.Cast<ConstantExpression>().Select(c => c.Value).ToArray();
            var value = node.Constructor.Invoke(args);
            var cex = Expression.Constant(value);

            return Visit(cex);
        }