C# IQueryable类代码示例

        public void Country_Get_All()
        {
            //Arrange
            data = new List<Country>() {
           new Country() { Id = 1, Name = "US" },
           new Country() { Id = 2, Name = "India" },
           new Country() { Id = 3, Name = "Russia" }
          }.AsQueryable();
            mockContext = new Mock<IContext>();
            mockSet = new Mock<IDbSet<Country>>();

           
            mockSet.Setup(m => m.Provider).Returns(data.Provider);
            mockSet.Setup(m => m.Expression).Returns(data.Expression);
            mockSet.Setup(m => m.ElementType).Returns(data.ElementType);
            mockSet.Setup(m => m.GetEnumerator()).Returns(data.GetEnumerator());

            mockContext.SetupGet(c => c.Countries).Returns(mockSet.Object);

            _service = new CountryService(mockContext.Object);


            //Act
            IQueryable<Country> results = _service.GetAll() as IQueryable<Country>;

            //Assert
            Assert.IsNotNull(results);
            Assert.AreEqual(3, results.ToList().Count);

         
        }

        /// <summary>
        /// Applies the roles filter.
        /// </summary>
        /// <param name="query">The query.</param>
        /// <param name="model">The model.</param>
        /// <returns>Query with roles filter applied</returns>
        private IQueryable<Models.User> ApplyRolesFilter(IQueryable<Models.User> query, GetUsersModel model)
        {
            if (model.FilterByRoles != null && model.FilterByRoles.Any(role => !string.IsNullOrWhiteSpace(role)))
            {
                var predicate = (model.FilterByRolesConnector == FilterConnector.Or)
                    ? PredicateBuilder.False<Models.User>()
                    : PredicateBuilder.True<Models.User>();

                foreach (var roleName in model.FilterByRoles)
                {
                    if (!string.IsNullOrWhiteSpace(roleName))
                    {
                        Expression<Func<Models.User, bool>> whereClause = user => user.UserRoles.Any(userRole => userRole.Role.Name == roleName && !userRole.Role.IsDeleted);
                        if (model.FilterByRolesConnector == FilterConnector.Or)
                        {
                            predicate = PredicateBuilder.Or(predicate, whereClause);
                        }
                        else
                        {
                            predicate = PredicateBuilder.And(predicate, whereClause);
                        }
                    }
                }

                query = query.Where(predicate);
            }

            return query;
        }

 public static List<BlogPostVModel> BlogPosts(IQueryable<SeqPost> result)
 {
     List<BlogPostVModel> blogList = new List<BlogPostVModel>();
     BlogPostVModel post;
     if (result == null) return blogList;
     foreach (SeqPost sp in result) {
         post = new BlogPostVModel();
         post.BlogPostId = sp.PostId;
         post.Title = sp.Title;
         post.Description = sp.Description;
         post.ExtendedDescription = sp.ExtendedText;
         post.Excerpt = sp.Excerpt;
         post.CreateDate = sp.CreateDate;
         post.Permalink = sp.Permalink;
         foreach (SeqTag st in sp.SeqTags) {
            TagVModel tvm = new TagVModel();
            tvm.BlogId = st.BlogId;
            tvm.TagId = st.TagId;
            tvm.Name = st.Name;
            post.Tags.Add(tvm);
         }
         blogList.Add(post);
     }
     return blogList;
 }

		public UpdatedPackages(
			IQueryable<IPackage> installedPackages,
			IPackageRepository aggregrateRepository)
		{
			this.installedPackages = installedPackages;
			this.sourceRepository = aggregrateRepository;
		}

        public override IQueryable GetQueryable(IQueryable source)
        {
            string selectedValue = DropDownList1.SelectedValue;
            if (String.IsNullOrEmpty(selectedValue))
            {
                return source;
            }

            if (selectedValue == NullValueString)
            {
                return ApplyEqualityFilter(source, Column.Name, null);
            }

            IDictionary dict = new Hashtable();
            Column.ExtractForeignKey(dict, selectedValue);
            foreach (DictionaryEntry entry in dict)
            {
                string key = (string)entry.Key;
                if (DefaultValues != null)
                {
                    DefaultValues[key] = entry.Value;
                }
                source = ApplyEqualityFilter(source, Column.GetFilterExpression(key), entry.Value);
            }
            return source;
        }

        /// <summary>
        /// Filters the device list with the supplied filters
        /// </summary>
        /// <param name="list">Devices to filter</param>
        /// <param name="filters">Filters to apply</param>
        /// <returns>Set of devices that pass all the filters</returns>
        public static IQueryable<dynamic> FilterDeviceList(
            IQueryable<dynamic> list, 
            List<FilterInfo> filters)
        {
            if (list == null)
            {
                throw new ArgumentNullException("list");
            }

            if (filters == null)
            {
                return list;
            }

            list = list.Where(GetIsNotNull).AsQueryable();

            foreach (var f in filters)
            {
                if ((f != null) && !string.IsNullOrEmpty(f.ColumnName))
                {
                    list = FilterItems(list, f);
                }
            }

            return list;
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="BaseCollectionResult" /> class.
        /// </summary>
        /// <param name="query">The query that returns a collection of objects.</param>
        /// <param name="edmType">The EDM type reference of the objects.</param>
        /// <param name="context">The context where the action is executed.</param>
        protected BaseCollectionResult(IQueryable query, IEdmTypeReference edmType, ApiContext context)
            : base(edmType, context)
        {
            Ensure.NotNull(query, "query");

            this.Query = query;
        }

        private static IQueryable<Customer> FilterCustomers(IQueryable<Customer> customers, Rule rule)
        {
            if (rule.field == "CustomerId")
            {
                int result;
                if (!int.TryParse(rule.data, out result))
                    return customers;
                return customers.Where(c => c.CustomerID == Convert.ToInt32(rule.data));

            }
            if (rule.field == "Name")
                return from c in customers
                       where c.FirstName.Contains(rule.data) || c.LastName.Contains(rule.data)
                       select c;
            if (rule.field == "Company")
                return customers.Where(c => c.CompanyName.Contains(rule.data));
            if (rule.field == "EmailAddress")
                return customers.Where(c => c.EmailAddress.Contains(rule.data));
            if (rule.field == "Last Modified")
            {
                DateTime result;
                if (!DateTime.TryParse(rule.data, out result))
                    return customers;
                if (result < new DateTime(1754, 1, 1)) // sql can't handle dates before 1-1-1753
                    return customers;
                return customers.Where(c => c.ModifiedDate.Date == Convert.ToDateTime(rule.data).Date);
            }
            if (rule.field == "Telephone")
                return customers.Where(c => c.Phone.Contains(rule.data));
            return customers;
        }

        public static MvcHtmlString CreateFilteredRequestTable(this HtmlHelper helper, IQueryable<FilteredRequestRecord> filteredRequestRecords, Localizer T)
        {
            StringBuilder sb = new StringBuilder();

            if (filteredRequestRecords == null || !filteredRequestRecords.Any())
            {
                sb.AppendLine(T("No requests are filtered yet.").Text);
            }
            else
            {
                sb.AppendLine("<table><tr>");
                sb.AppendFormat("<th>{0}</th>", T("Request time"));
                sb.AppendFormat("<th>{0}</th>", T("Url"));
                sb.AppendFormat("<th>{0}</th>", T("User Host Address"));
                sb.AppendFormat("<th>{0}</th>", T("User Agent"));
                sb.AppendLine("</tr>");

                foreach (FilteredRequestRecord filteredRequest in filteredRequestRecords.OrderByDescending(r => r.RequestTime))
                {
                    sb.AppendLine("<tr>");
                    sb.AppendFormat("<td>{0}</td>", filteredRequest.RequestTime);
                    sb.AppendFormat("<td>{0}</td>", filteredRequest.Url);
                    sb.AppendFormat("<td>{0}</td>", filteredRequest.UserHostAddress);
                    sb.AppendFormat("<td>{0}</td>", filteredRequest.UserAgent);
                    sb.AppendLine("</tr>");
                }
                sb.AppendLine("</table>");
            }
            return new MvcHtmlString(sb.ToString());
        }

        public override Expression BuildLinqExpression(IQueryable query, Expression expression, Expression item = null)
        {
            var leftExpression = this.LeftNode.BuildLinqExpression(query, expression, item);
            var rightExpression = this.RightNode.BuildLinqExpression(query, expression, item);

            // Nasty workaround to avoid comparison of Aggregate functions to true or false which breaks Entity framework
            if (leftExpression.Type == typeof(bool) && rightExpression.Type == typeof(bool) && rightExpression is ConstantExpression)
            {
                if ((bool)(rightExpression as ConstantExpression).Value)
                {
                    return leftExpression;
                }

                return Expression.Not(leftExpression);
            }

            if (rightExpression.Type == typeof(bool) && leftExpression.Type == typeof(bool)
                && leftExpression is ConstantExpression)
            {
                if ((bool)(leftExpression as ConstantExpression).Value)
                {
                    return rightExpression;
                }

                return Expression.Not(rightExpression);
            }

            NormalizeTypes(ref leftExpression, ref rightExpression);

            return ApplyEnsuringNullablesHaveValues(Expression.Equal, leftExpression, rightExpression);
        }

        public PackageListViewModel(
            IQueryable<Package> packages,
            DateTime? indexTimestampUtc,
            string searchTerm,
            int totalCount,
            int pageIndex,
            int pageSize,
            UrlHelper url,
            string curatedFeed)
        {
            // TODO: Implement actual sorting
            IEnumerable<ListPackageItemViewModel> items = packages.ToList().Select(pv => new ListPackageItemViewModel(pv));
            PageIndex = pageIndex;
            IndexTimestampUtc = indexTimestampUtc;
            PageSize = pageSize;
            TotalCount = totalCount;
            SearchTerm = searchTerm;
            int pageCount = (TotalCount + PageSize - 1) / PageSize;

            var pager = new PreviousNextPagerViewModel<ListPackageItemViewModel>(
                items,
                PageIndex,
                pageCount,
                page => curatedFeed == null ?
                    url.PackageList(page, searchTerm) :
                    url.CuratedPackageList(page, searchTerm, curatedFeed)
                );
            Items = pager.Items;
            FirstResultIndex = 1 + (PageIndex * PageSize);
            LastResultIndex = FirstResultIndex + Items.Count() - 1;
            Pager = pager;
        }

        public static MemberAccessExpressionBuilderBase MemberAccess(IQueryable source, Type memberType, string memberName)
        {
            var builder = MemberAccess(source.ElementType, memberType, memberName);
            builder.Options.LiftMemberAccessToNull = source.Provider.IsLinqToObjectsProvider();

            return builder;
        }

        public PackageListViewModel(IQueryable<Package> packages,
            string searchTerm,
            string sortOrder,
            int totalCount,
            int pageIndex,
            int pageSize,
            UrlHelper url,
            bool includePrerelease)
        {
            // TODO: Implement actual sorting
            IEnumerable<ListPackageItemViewModel> items;
            using (MiniProfiler.Current.Step("Querying and mapping packages to list"))
            {
                items = packages.ToList()
                                .Select(pv => new ListPackageItemViewModel(pv, needAuthors: false));
            }
            PageIndex = pageIndex;
            PageSize = pageSize;
            TotalCount = totalCount;
            SortOrder = sortOrder;
            SearchTerm = searchTerm;
            int pageCount = (TotalCount + PageSize - 1) / PageSize;

            var pager = new PreviousNextPagerViewModel<ListPackageItemViewModel>(
                items,
                PageIndex,
                pageCount,
                page => url.PackageList(page, sortOrder, searchTerm, includePrerelease)
            );
            Items = pager.Items;
            FirstResultIndex = 1 + (PageIndex * PageSize);
            LastResultIndex = FirstResultIndex + Items.Count() - 1;
            Pager = pager;
            IncludePrerelease = includePrerelease ? "true" : null;
        }

        public IQueryable<EnhancedStudentInformation> ApplyFilter(IQueryable<EnhancedStudentInformation> query, StudentMetricsProviderQueryOptions providerQueryOptions)
        {
            //If the Staff USI Isn't set, then no-op.
            if (providerQueryOptions.StaffUSI <= 0)
                return query;

            //The only way a Staff member can be associated with a student at LEA is via the Staff Cohort tables.  Only check that one table.
            if (providerQueryOptions.LocalEducationAgencyId.HasUsableValue() && !providerQueryOptions.SchoolId.HasUsableValue())
            {
                var staffStudentCohorts = StaffStudentCohortRepository.GetAll();
                IQueryable<StaffCohort> staffCohort = StaffCohortRepository.GetAll().Where(sc => sc.StaffUSI == providerQueryOptions.StaffUSI);

                return query.Where(si => staffStudentCohorts
                    .SelectMany(ssc => staffCohort.Where(sc => ssc.StaffCohortId == sc.StaffCohortId).Select(sc => ssc))
                    .Any(ssc => ssc.StudentUSI == si.StudentUSI));
            }

            //At the school level, a staff member can be associated by Cohort or by Section.  This view collapses the two.
            var ssa = StaffStudentAssociationRepository.GetAll();
            return query.Where(student => ssa.Any(ms => ms.StudentUSI == student.StudentUSI
                                                        && ms.SchoolId == student.SchoolId
                //This filters on school id, because if a teacher is a teacher at two schools,
                //We need to filter on the Staff Section records only for the current school.
                                                        && ms.SchoolId == providerQueryOptions.SchoolId.GetValueOrDefault()
                                                        && ms.StaffUSI == providerQueryOptions.StaffUSI));
        }

        public IQueryable ApplySelectAndExpand(IQueryable queryable, HttpRequestMessage request )
        {
            var result = queryable;
              var hasSelectOrExpand = false;

              var map = request.RequestUri.ParseQueryString();

              var selectQueryString = map["$select"];
              if (!string.IsNullOrWhiteSpace(selectQueryString)) {
            var selectClauses = selectQueryString.Split(',').Select(sc => sc.Replace('/', '.')).ToList();
            var elementType = TypeFns.GetElementType(queryable.GetType());
            var func = QueryBuilder.BuildSelectFunc(elementType, selectClauses);
            result = func(result);
            hasSelectOrExpand = true;
              }

              var expandsQueryString = map["$expand"];
              if (!string.IsNullOrWhiteSpace(expandsQueryString)) {
            if (!string.IsNullOrWhiteSpace(selectQueryString)) {
              throw new Exception("Use of both 'expand' and 'select' in the same query is not currently supported");
            }
            expandsQueryString.Split(',').Select(s => s.Trim()).ToList().ForEach(expand => {
              result = ((dynamic) result).Include(expand.Replace('/', '.'));
            });
            hasSelectOrExpand = true;
              }

              return hasSelectOrExpand ? result : null;
        }