https://msdn.microsoft.com/en-us/library/bb397676(v=vs.100).aspx Language-Integrated Query (LINQ) is the name for a set of technologies based on the integration of query capabilities能力 directly into the C# language (also in Visual Basic and potential…

1.只能对 Type.IsGenericParameter 为 True 的类型调用方法 对于此错误,一般常见在虚拟实体,但是要把条件拼接在Expression中,通常是因为该字段在数据库中是可空的,做法就是将此条件在Linq Query之前先过来,不要用来过滤虚拟的实体,用来过滤原生的实体…

1.查询语法 Query Syntax: from <range variable> in <IEnumerable<T> or IQueryable<T> Collection> <Standard Query Operators> <lambda expression> <select or groupBy operator> <result formation> // string collection…

var t = from x in context.NewsLetterItem.ToList() //add .ToList at this place where x.APPId == appid && allowedAddress.Contains(x.mailFrom) orderby int.Parse(x.mailId) descending select x; else, if you use the following query,  an erro with follow…

我们知道Linq to sharepoint 实际最终还是转化成了CALM来对Sharepoint进行访问,那么我们怎样才能知道我们编写的Query语句最终转化成的CALM语句是什么样子呢. 我们可以使用如下方法来达到我们的目的. 1.首先在我们的Sharepoint项目中新建一个名为CAMLDebug的类,如图: CALMDebug.cs代码如下:   using System;using System.Collections.Generic;using System.Linq;using S…

延迟执行是指一个表达式的值延迟获取,知道它的值真正用到. 当你用foreach循环时,表达式才真正的执行. 延迟执行有个最重要的好处:它总是给你最新的数据 实现延迟运行 你可以使用yield关键字实现延迟加载 public static class EnumerableExtensionMethods { public static IEnumerable<Student> GetTeenAgerStudents(this IEnumerable<Student> source)…

最近在看neuecc大佬写的一些库:https://neuecc.medium.com/,其中对await,async以及linq一些关键字实现了自定义化使用, 使其不需要引用对应命名空间,不需要多线程就可以做一些自定义操作.因此进行学习,并在Unity3D下进行测试. 1.await,async关键字的自定义化扩展 只需要实现GetAwaiter公共方法即可,通过扩展方法实现也可以: public static CoroutineAwaiter<WaitForSeconds> GetAwai…

Sometimes the LINQ, Query Expressions or Fetch just doesn't give you the ability to quickly query your data in the way you want to. A good example of this is the lack of left outer join support if you want a where clause to filter results based on th…

class Program { static void Main(string[] args) { List<Person> persons = new List<Person>() { ,Name="lin1"}, ,Name="lin2"}, ,Name="lin3"} }; Person person = persons.Find( delegate(Person p) //this is an anonymous…

Overloads Join(String, String[], Int32, Int32) Concatenates the specified elements of a string array, using the specified separator between each element. Join(String, String[]) Concatenates all the elements of a string array, using the specified sepa…