下列範例顯示簡單的「查詢運算式」(Query Expression),以及在語意上相等,以「方法架構查詢」(Method-Based Query) 撰寫的對等查詢。 C# 複製 class QueryVMethodSyntax { static void Main() { int[] numbers = { 5, 10, 8, 3, 6, 12}; //Query syntax: IEnumerable<int> numQuery1 = from num in...
The following table classifies each standard query operator method according to its method of execution. Note If an operator is marked in two columns, two input sequences are involved in the operation, and each sequence is evaluated differently. In these cases, it is always the first sequence ...
inqueryMajorCities) { Console.WriteLine(city); }// Output:// City { Name = Tokyo, Population = 37833000 }// City { Name = Delhi, Population = 30290000 }// Method-based syntaxIEnumerable<City> queryMajorCities2 = cities.Where(c => c.Population >30_000_000);// Execute the query to...
Linq查询的两种方式 (1) Method syntax,查询方法方式 主要利用System.Linq.Enumerable类中定义的扩展方法和Lambda表达式方式进行查询。 (2) Query syntax ,查询语句方式 查询语句VS查询方法 注:查询语句和查询方法存在着紧密的关系 (1) CLR本身并不理解查询语句,它只理解查询方法。 (2) 编译器负责在编译时将查询语...
Query Expression Query Operator Expression Tree 和Expression的区别类似XmlNode和XmlElement的区别。Expression Tree用于表达对IQueryable<T>类型数据源的查询树,是Select/Where/From等多个Query method嵌套,在运行时LINQ2SQL会根据Expression Tree来生成SQL语句。 Expression 确切的说是Expression类,为Expression Tree的每一...
SequenceEqual<TSource>(IQueryable<TSource>, IEnumerable<TSource>)方法會產生MethodCallExpression,代表呼叫SequenceEqual<TSource>(IQueryable<TSource>, IEnumerable<TSource>)本身做為建構的泛型方法。 然後,它會將MethodCallExpression傳遞至source1參數Provider屬性所表示之IQueryProvider的Execute<TResult>(Expression)...
In the example above, the Where extension method extends the type IEnumerable<T>. Because Where is a static method, we can invoke it directly just like any other static method: Copy IEnumerable<string> query = Enumerable.Where(names, s => s.Length < 6); However, what makes extension ...
方法FirstOrDefault<TSource>(IQueryable<TSource>) 生成一个 , MethodCallExpression 表示将调用 FirstOrDefault<TSource>(IQueryable<TSource>) 自身作为构造的泛型方法。 然后,MethodCallExpressionExecute<TResult>(Expression)它将 传递给 由 Provider 参数的 属性表示的 的 source 方法IQueryProvider。 由于执行表...
classQueryVMethodSyntax{staticvoidMain(){int[] numbers = {5,10,8,3,6,12};//Query syntax:IEnumerable<int> numQuery1 =fromnuminnumberswherenum %2==0orderbynumselectnum;//Method syntax:IEnumerable<int> numQuery2 = numbers.Where(num => num %2==0).OrderBy(n => n);foreach(intiinnum...
It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter. The query behavior that occurs as a result of executing an expression tree that represents calling Sum(IQueryable<Int...