扩展MongoDB C# Driver的QueryBuilder

由于不想直接hardcode "ClassA.MemberA.MemberB" 这样的字符串 ，写了以下几个类，用于以下常用的场景：
1. 表达式转换成字符串函数： ExpToStr()
2. Collection函数：当有集合成员时，可以使用此类，将返回QueryCollection对象，这个类的代码之后附上
3. CollectionAs函数：当使用了继承，希望将基类转换为子类并返回子类的QueryCollection

使用示例：

//获得表达式的字符串形式
1. QueryEx<ClassA>.ExpToStr ((ClassA m)=> m.MemberA.MemberB.MemberC)

//集合.成员.字段
//PoppedSegments为集合，AssignedNetwork.Name为成员
//将返回PoppedSegments.AssignedNetwork.Name
2. QueryEx<MDDelivery>.Collection(x => x.PoppedSegments).Matches(p => p.AssignedNetwork.Name, bsonRegex),

//子类集合.成员.字段
//STPaymentTransaction为基类，STPaymentCompanyCredit为子类，Company字段在子类中
//将返回Payments.Company.Name
3. QueryEx<MDDelivery>.CollectionAs<STPaymentTransaction, STPaymentCompanyCredit>(x=>x.Payments).Matches(p=>p.Company.Name, bsonRegex)


//集合.集合.成员.字段
//Parcels为集合，STCustomPropertyRuntime为基类，STNumericPropertyRuntime为子类，CustomProps为STNumericPropertyRuntime中成员，Value为CustomProp中成员
//将返回Parcels.CustomProps.Value
4. QueryEx<MDDelivery>.Collection(x=>x.Parcels).CollectionMemberAs<STCustomPropertyRuntime, STNumericPropertyRuntime>(p=>p.CustomProps).Matches(p=>p.Value, bsonRegex),

实现代码：

public class QueryEx<TDocument>
    {
        public static QueryCollection<TDocument, TCollection> Collection<TCollection>(
            Expression<Func<TDocument, IEnumerable<TCollection>>> collectionExpression)
        {
            return new QueryCollection<TDocument, TCollection>(collectionExpression);
        }


        //for those cases using inheritance
        //e.g STPaymentTransaction
        //Payments will return STPaymentTransaction 
        //need to cast to sub classes(STPaymentCompanyCredit) so that be able to filter by child members (e.g. Company)
        public static QueryCollection<TDocument, TSub> CollectionAs<TCollection, TSub>(
            Expression<Func<TDocument, IEnumerable<TCollection>>> collectionExpression)
            where TSub : TCollection
        {
            var argParam = Expression.Parameter(typeof (TDocument), "x");
            var memberStr = ExpToStr(collectionExpression);
            MemberExpression nameProperty = Expression.Property(argParam, memberStr);


            var subExp = Expression.Convert(nameProperty, typeof(IEnumerable<TSub>));


            var exp = Expression.Lambda<Func<TDocument, IEnumerable<TSub>>>(
                subExp,
                argParam);


            return new QueryCollection<TDocument, TSub>(exp);
        }


        /// <summary>
        /// return string value for a expression:
        /// for s.Name.Val1.Val2 will return Name.Val1.Val2
        /// </summary>
        /// <typeparam name="MDClass"></typeparam>
        /// <typeparam name="Member"></typeparam>
        /// <param name="exp"></param>
        /// <returns></returns>
        public static string ExpToStr<TDocument, Member>(Expression<Func<TDocument, Member>> exp)
        {
            return new QueryExpressionHelper().MemberExpression(exp);
        }
    }

public class QueryCollection<TDocument, TCollection>
    {
        private readonly QueryExpressionHelper _queryExpression;
        private string _collectionName;


        public string Context
        {
            get { return _collectionName; }
        }


        public QueryCollection(Expression<Func<TDocument, IEnumerable<TCollection>>> collectionExpression)
        {
            _queryExpression = new QueryExpressionHelper();
            _collectionName = _queryExpression.MemberExpression(collectionExpression);
        }


        public QueryMember<TCollection, TMember> Member<TMember>(Expression<Func<TCollection, TMember>> exp)
        {
            var expStr = QueryEx<TCollection>.ExpToStr(exp);
            var context = string.Format("{0}.{1}", _collectionName, expStr);
            var obj = new QueryMember<TCollection, TMember>(context);

            return obj;
        }

        public QueryCollection<TCollection, TMember> CollectionMember<TMember>(
            Expression<Func<TCollection, IEnumerable<TMember>>> exp)
        {
            var expStr = QueryEx<TCollection>.ExpToStr(exp);
            var obj = new QueryCollection<TCollection, TMember>(exp)
            {
                _collectionName = string.Format("{0}.{1}", _collectionName, expStr)
            };

            return obj;
        }


        /// <summary>
        /// this method only support 1 layer nested(not for Query Collection.Collection , but for Collection.Member)
        /// if member is collection and need convert to sub class 
        /// </summary>
        /// <typeparam name="TMember">Base Type</typeparam>
        /// <typeparam name="TMemberSub">Child Class Type</typeparam>
        /// <param name="collectionExpression"></param>
        /// <returns></returns>
        public QueryCollection<TCollection, TMemberSub> CollectionMemberAs<TMember, TMemberSub>(
            Expression<Func<TCollection, IEnumerable<TMember>>> collectionExpression)
            where TMemberSub : TMember
        {
            var obj = QueryEx<TCollection>.CollectionAs<TMember, TMemberSub>(collectionExpression);
            obj._collectionName = string.Format("{0}.{1}", _collectionName, obj._collectionName);

            return obj;
        }

        public IMongoQuery LT<TMember>(Expression<Func<TCollection, TMember>> memberExpression, TMember value)
        {
            var memberName = _queryExpression.MemberExpression(memberExpression);


            return Query.LT(string.Format("{0}.{1}", _collectionName, memberName), BsonValue.Create(value));
        }


        public IMongoQuery LT<TValue>(Expression<Func<TCollection, IEnumerable<TValue>>> memberExpression, TValue value)
        {
            var memberName = _queryExpression.MemberExpression(memberExpression);


            return Query.LT(string.Format("{0}.{1}", _collectionName, memberName), BsonValue.Create(value));
        }


        public IMongoQuery EQ<TMember>(Expression<Func<TCollection, TMember>> memberExpression, TMember value)
        {
            var memberName = _queryExpression.MemberExpression(memberExpression);


            return Query.EQ(string.Format("{0}.{1}", _collectionName, memberName), BsonValue.Create(value));
        }


        public IMongoQuery EQ<TValue>(Expression<Func<TCollection, IEnumerable<TValue>>> memberExpression, TValue value)
        {
            var memberName = _queryExpression.MemberExpression(memberExpression);


            return Query.EQ(string.Format("{0}.{1}", _collectionName, memberName), BsonValue.Create(value));
        }


        public IMongoQuery NE<TMember>(Expression<Func<TCollection, TMember>> memberExpression, TMember value)
        {
            var memberName = _queryExpression.MemberExpression(memberExpression);


            return Query.NE(string.Format("{0}.{1}", _collectionName, memberName), BsonValue.Create(value));
        }


        public IMongoQuery NE<TValue>(Expression<Func<TCollection, IEnumerable<TValue>>> memberExpression, TValue value)
        {
            var memberName = _queryExpression.MemberExpression(memberExpression);


            return Query.NE(string.Format("{0}.{1}", _collectionName, memberName), BsonValue.Create(value));
        }


        public IMongoQuery In<TMember>(Expression<Func<TCollection, TMember>> memberExpression, params TMember[] values)
        {
            return In<TMember>(memberExpression, new List<TMember>(values));
        }


        public IMongoQuery In<TMember>(Expression<Func<TCollection, TMember>> memberExpression,
            IEnumerable<TMember> values)
        {
            var memberName = _queryExpression.MemberExpression(memberExpression);
            return Query.In(string.Format("{0}.{1}", _collectionName, memberName), values.Select(x => BsonValue.Create(x)));
        }


        public IMongoQuery In<TCastC, TMember>(Expression<Func<TCastC, TMember>> memberExpression,
            IEnumerable<TMember> values) where TCastC : TCollection
        {
            var memberName = _queryExpression.MemberExpression(memberExpression);
            return Query.In(string.Format("{0}.{1}", _collectionName, memberName), values.Select(x => BsonValue.Create(x)));
        }


        public IMongoQuery In<TValue>(Expression<Func<TCollection, IEnumerable<TValue>>> memberExpression, IEnumerable<TValue> values)
        {
            var memberName = _queryExpression.MemberExpression(memberExpression);
            return Query.In(string.Format("{0}.{1}", _collectionName, memberName), values.Select(x => BsonValue.Create(x)));
        }


        public IMongoQuery In<TCastC, TValue>(Expression<Func<TCastC, IEnumerable<TValue>>> memberExpression, IEnumerable<TValue> values) where TCastC : TCollection
        {
            var memberName = _queryExpression.MemberExpression(memberExpression);
            return Query.In(string.Format("{0}.{1}", _collectionName, memberName), values.Select(x => BsonValue.Create(x)));
        }




        public IMongoQuery Matches<TMember>(Expression<Func<TCollection, TMember>> memberExpression, BsonRegularExpression value)
        {
            var memberName = _queryExpression.MemberExpression(memberExpression);


            return Query.Matches(string.Format("{0}.{1}", _collectionName, memberName), value);
        }


        public IMongoQuery Matches<TValue>(Expression<Func<TCollection, IEnumerable<TValue>>> memberExpression, BsonRegularExpression value)
        {
            var memberName = _queryExpression.MemberExpression(memberExpression);


            return Query.Matches(string.Format("{0}.{1}", _collectionName, memberName), value);
        }
    }

public class QueryMember<TDocument, TCollection>
    {
        private readonly QueryExpressionHelper _queryExpression;
        private string _collectionName;


        public string Context
        {
            get { return _collectionName; }
        }


        public QueryMember(Expression<Func<TDocument, TCollection>> exp)
        {
            _queryExpression = new QueryExpressionHelper();
            _collectionName = _queryExpression.MemberExpression(exp);
        }


        public QueryMember(string context)
        {
            _collectionName = context;
        }


    }

public class QueryExpressionHelper
    {
        public string Context;


        public string MemberExpression<TMember>(Expression<TMember> expression)
        {
            MemberExpression me;
            switch (expression.Body.NodeType)
            {
                case ExpressionType.MemberAccess:
                    me = expression.Body as MemberExpression;
                    break;
                case ExpressionType.Convert:
                    dynamic convertedBody = expression.Body;
                    me = convertedBody.Operand as MemberExpression;
                    break;


                default:
                    throw new NotSupportedException(string.Format("Member with node type {0} is not supported. expression {1}", expression.Body.NodeType, expression));
            }
            var stack = new Stack<string>();


            while (me != null)
            {
                stack.Push(me.Member.Name);
                me = me.Expression as MemberExpression;
            }


            var expStr = string.Join(".", stack.ToArray());
            return expStr;


           
        }
    }




public static class QueryMoney
    {
        public static IMongoQuery Value(string name, double val)
        {
            var accuracy = 0.005;


            return Query.And(
                Query.LT(name, new BsonDouble(val + accuracy)),
                Query.GT(name, new BsonDouble(val - accuracy)));
        }
    }