select count(*) Select DISTINCT in LEFT JOIN SELECT DISTINCT on one column, with multiple columns returned Select event where date >= today SELECT INTO temporary table with unique key? SELECT not DISTINCT records in Table Select with from database with a list of parameters Selecting columns from...
与ToList()方法类似,通过调用ToArray()方法,可以将查询结果转换为一个基于值的引用。例如: 代码语言:csharp 复制 var query = from item in collection where item.Property == value select item; Item[] result = query.ToArray(); 需要注意的是,使用ToList()或ToArray()方法会在内存中创建一个新的集合...
DimqueryResults =FromcustIncustomersWherecust.Country ="Canada"Selectcust.CompanyName, cust.Country 还可使用 LINQ 查询合并多个数据源组并返回单个结果。 可以使用一个或多个From子句,或者使用Join或Group Join查询子句来完成此操作。 下面的代码示例演示了一个查询表达式,它合并客户和订单数据,并返回包含客户和订...
DimqueryResults =FromcustIncustomersWherecust.Country ="Canada"Selectcust.CompanyName, cust.Country 还可使用 LINQ 查询合并多个数据源组并返回单个结果。 可以使用一个或多个From子句,或者使用Join或Group Join查询子句来完成此操作。 下面的代码示例演示了一个查询表达式,它合并客户和订单数据,并返回包含客户和订...
var length = 1; var qry = companyNamesSource .Select(x => x.Substring(0, length)) .Distinct(); Console.WriteLine(string.Join(",", qry)); // prints: C, A, S, W, G, H, M, N, B, T, L, F length = 2; Console.WriteLine(string.Join(",", qry)); // prints: Co, ...
Use thewhereclause to filter out elements from the source data based on one or more predicate expressions. Thewhereclause in the following example has one predicate with two conditions. C# IEnumerable<City> queryCityPop =fromcityincitieswherecity.Populationis<15_000_000and>10_000_000selectcity; ...
varlength =1;varqry = companyNamesSource .Select(x => x.Substring(0, length)) .Distinct(); Console.WriteLine(string.Join(",", qry));// prints: C, A, S, W, G, H, M, N, B, T, L, Flength =2; Console.WriteLine(string.Join(",", qry));// prints: Co,...
var names = from c in myCars select c.PetName;这里names就是隐式类型的变量。 3、使用Enumerable.Distinct<T>() var makes = (from c in myCars select c.Make).Distinct<string>(); 4、即可以在定义的时候调用Enumberalbe扩展函数 var names = from c in myCars select c.PetName; ...
publicstaticIEnumerable<TSource>Distinct<TSource>( thisIEnumerable<TSource>source,IEqualityComparer<TSource>comparer) {/* code removed*/} // and many more 扩展方法介绍 Where and Select Where 和Select是两个定义在Ienumerable<TSource>接口中非常重要的方法.它们的定义如下: ...
select new { CompanyName = customer.CompanyName, ContactName = customer.ContactName, Phone = customer.Phone, TotalSpend = customer.TotalSpend }).Take(5) ).ToList() // format the data as XML select new XElement("Customer", new XAttribute("companyName", top5.CompanyName), new XAttribute...