// 方法语法 var GroupByMS = Student.GetStudents().ToLookup(s => s.Branch); // 查询语法 var GroupByQS = (from std in Student.GetStudents() select std).ToLookup(x => x.Branch); foreach (var group in GroupByMS) { Console.WriteLine(group.Key + " : " + group.Count()); foreach...
OrderBy / OrderByDescending: 用于排序数据。 Select: 用于投影数据。 GroupBy: 用于分组数据。 Join: 用于连接两个数据源。 ToList / ToArray: 将查询结果转换为列表或数组。 Count: 返回元素数量。 First / FirstOrDefault: 返回第一个元素。 Single / SingleOrDefault: 返回单个元素。 Aggregate: 对序列中的...
BinaryExpression comparison=Expression.GreaterThan(property, constant);//构建 Lambda 表达式Expression<Func<Person,bool>> lambda = Expression.Lambda<Func<Person,bool>>(comparison, parameter);//编译表达式树并使用Func<Person,bool> func =lambda.Compile();//测试查询条件varpeople =new[] {newPerson { Nam...
CountAsync() 10 ; 11 var pagerows = (await this.companyService 12 .Query(filters) 13 .AsNoTracking() 14 .OrderBy(n => n.OrderBy(sort, order)) 15 .Skip(page - 1).Take(rows) 16 .SelectAsync()) 17 .Select(n => new 18 { 19 Id = n.Id, 20 Name = n.Name, 21 Code = n...
() group std by std.Barnch); //It will iterate through each groups foreach (IGrouping<string, Student> group in GroupByMS) { Console.WriteLine(group.Key + " : " + group.Count()); //Iterate through each student of a group foreach (var student in group) { Console.WriteLine(" Name...
Into … Count Count Aggregate … Into … LongCount LongCount Aggregate … Into … Max Max Aggregate … Into … Min Min Aggregate … Into … Sum Sum Distinct Distinct Group By GroupBy Group Join GroupJoin Order By OrderBy Order By … Descending OrderByDescending Order By (with multi...
(subGroup, parameter, propertyMap));42}4344if(expressions.Count ==0)45{46thrownewInvalidOperationException("构造where子句异常,生成了0个比较条件表达式。");47}4849if(expressions.Count ==1)50{51returnexpressions[0];52}5354varexpression = expressions[0];55switch(group.GroupOp)56{57case"AND":58...
In the following example, query #7 returns a count of the numbers whose value is between 3 and 7. C# Copy // Query #7. // Using a query expression with method syntax var numCount1 = ( from num in numbers1 where num is > 3 and < 7 select num ).Count(); // Better: Create...
Using a query expression with method syntaxvarnumCount1 = (fromnuminnumbers1wherenumis>3and<7selectnum ).Count();// Better: Create a new variable to store// the method call resultIEnumerable<int> numbersQuery =fromnuminnumbers1wherenumis>3and<7selectnum;varnumCount2 = numbersQuery.Count();...
groupId。// check for duplicate value by checking whether the count is greater than or equal to...