多个表中加入LINQ的C＃动态 [英] Multiple Table Join in Linq C# Dynamically

问题描述

我有3个数据表： A ; B ;和 C 。在此我需要写连接查询动态使用的 LINQ

I have 3 data tables: a; b; and c. In this I need to write Join Query Dynamically using LINQ.

由客户和条件列给出的选择列也给予客户在运行时。

The Selecting columns given by customer and Condition columns also given customer at run time.

所以我需要动态地创建查询。请检查下面的例子。因为我不知道他们要和列还

So I need to create queries dynamically. Please check below example. Because I don't know which table they want and which column also

例如

Select a.c1,a.c2,b.c1,b.c2 From a Left Join b on a.c1=b.c1

Select c.c1,c.c2,a.c1,a.c2 From c Left Join a on c.c3=a.c1

Select a.c1,a.c2,b.c1,b.c2,c.c1,c.c2 From a Left Join b on a.c2=b.c2 Left join c on c.c1=a.c1

$ C b $ b

就像我需要创建不同的组查询。请帮我在这。

Like I need create different set of queries. Please help me on this.

推荐答案

您可以使用任何 System.Linq.Dynamic （ ScottGu的博客文章和的NuGet ）动态where子句的情况：

You could use either System.Linq.Dynamic(ScottGu's blog article and nuget) in case of dynamic where clause:

var results = (from fruit in fruits 
    join car in cars on fruit.Id equals car.Id
    select new { fruit, car })
    .AsQueryable()
    .Where("fruit.ColA != car.ColA")
    .Where("fruit.ColB == car.ColB");

或者dynamicaly构建表达式使用这个的从 PredicateBuilder 通过@乔 - 阿尔巴哈利writen扩展。例如：

Or dynamicaly build expressions this using extensions from PredicateBuilder writen by @joe-albahari. For example:

var predicate = 
    PredicateBuilder
        .True<Tuple<Product, Product>>()
        .And(t => t.Item1.ColA != t.Item2.ColA)
        .And(t => t.Item1.ColB == t.Item2.ColB)
        .Compile();    

(from fruit in fruits 
    join car in cars on fruit.Id equals car.Id
    select Tuple.Create(fruit, car))
    .Where(predicate)
    .Dump();

PS：在的 gisthub

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