动态Linq包含多个值 [英] Multiple Values Contains with Dynamic Linq

问题描述

如何在Dynamic Linq中将多值"与包含"一起使用.

How to use Multiple value with Contain in Dynamic Linq.

与Normal Linq一起使用:

using System;
using System.Linq;
public class Simple {
  public static void Main() {
    string[] names = { "Burke", "Laptop", "Computer", 
                       "Mobile", "Ahemed", "Sania", 
                       "Kungada", "David","United","Sinshia" };
      string[] vars = {"i","a"};
      var query = names.Where(i=> vars.Any(j=>i.Contains(j))).ToList();

      Console.WriteLine(query.Count);
  }
}

期望的SQL

SELECT * FROM User WHERE (NAME LIKE '%a%'OR NAME LIKE '%b%')

尝试过动态Linq:

query = query.Where("new[]{\"a\",\"c\"}.Any(i=>i.Contains(it.ProductName))");

返回异常:

No property or field 'ProductName' exists in type 'String'

依赖项:

• .NET CORE 2.2
• EntityFramework Core 2.2.6
• System.Linq.Dynamic.Core 1.0.18( https://github.com/StefH/System.Linq.Dynamic.Core)

推荐答案

尝试动态查询"有两个问题:

There are two issues with your "tried dynamic query":

1. 在转换为动态查询时，您混合了变量名称，因为 i 和 j 太相似了.

它含糊，因为有2个lambda，因此将其解析为最里面的lambda的参数.

it is ambigous as there are 2 lambdas and so it is parsed as a parameter of the innermost lambda.

我们首先将 i 重命名为 p (用于产品名称")，将 j 重命名为 s (用于搜索"):

Let's first rename i to p (for "product names") and j to s (for "search"):

var query = names.Where(p => vars.Any(s => p.Contains(s))).ToList();

然后，您可以将其直接转换为动态Linq表达式:

Then you can directly transform this to a dynamic Linq expression:

// The type of vars needs to be IEnumerable<string> otherwise Dynamic Linq does not see .Any
IEnumerable<string> vars = new[] {"i", "a"};
var query2 = names.Where("p => @0.Any(s => p.Contains(s))", vars).ToList();

然后，您可以将内部Lambda的参数替换为 it

Then you can replace the argument of inner lambda (s) with it

var query3 = names.Where("p => @0.Any(p.Contains(it))", vars).ToList();

如您所见，您混合了 Contains 的对象和参数.

As you can see you mixed up the object and argument of Contains.

然后，您可以将表达式应用于EF查询.因此，参数 p 的用法将变为 p.ProductName :

Then you can apply the expression the EF query. So usage of argument p becomes p.ProductName:

IEnumerable<string> vars = new[] {"i", "a"};
query = query.Where("p => @0.Any(p.ProductName.Contains(it))", vars).ToList();

或者像这样:

IEnumerable<string> vars = new[] {"i", "a"};
query = query.Where("p => @0.Any(s => p.ProductName.Contains(s))", vars).ToList();

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