LINQ To SQL IN與排序

最新推荐文章于 2019-07-06 08:53:00 发布

原创最新推荐文章于 2019-07-06 08:53:00 发布 · 7.1k 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#linq #sql #string #query #list #module

本文介绍了一种使用 C# 和 VB.NET 实现的自定义排序方法，该方法可以根据传入元素的顺序进行排序。通过 LINQ 查询指定城市列表，并使用自定义排序函数 CustomSort 对查询结果进行排序。

承上篇,讀者繼續詢問排序問題,如要依IN時傳入元素的順序排列,該如何做?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Linq;

namespace ConsoleApplication36
{
    class Program
    {
        static void Main(string[] args)
        {
            DataClasses1DataContext context = new DataClasses1DataContext();
            context.Log = Console.Out;
            var result = from s1 in context.Customers where (new string[] { "UK", "Lisboa" }).Contains(s1.City) select s1;
            var result2 = CustomSort(result.ToList(), new string[] { "UK", "Lisboa" });
            foreach (var item in result2)
            {
                Console.WriteLine(item.City);
            }
            Console.ReadLine();
        }

        static List<Customers> CustomSort(List<Customers> list,string[] citys)
        {
            List<Customers> result = new List<Customers>();
            foreach (var item in citys)
            {
                var query = from s1 in list where s1.City == item select s1;
                foreach (var ditem in query)
                    result.Add(ditem);
            }
            return result;
        }
    }
}

VB.NET

Module Module1

Sub Main()

Dim context As New DataClasses1DataContext()

        Dim lists = From s1 In context.Customers Where (New String() {"UK", "Lisboa"}).Contains(s1.City) Select s1
        For Each item In CustomSort(lists.ToList(), New String() {"UK", "Lisboa"})
            Console.WriteLine(item.City)
        Next
        Console.ReadLine()
    End Sub

    Function CustomSort(ByVal source As List(Of Customers), ByVal citys As String())
        Dim result As New List(Of Customers)
        For Each item In citys
            Dim localItem = item
            Dim query = From s1 In source Where s1.City = localItem Select s1
            For Each ditem In query
                result.Add(ditem)
            Next
        Next
        Return result
    End Function

End Module

請注意,ToList後即進入離線模式,接下來的CustomSort不會送出任何SQL指令.