Multiple Values Contains with Dynamic Linq

问题

How to use Multiple value with Contain in Dynamic Linq.

Expected With Normal Linq :

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);
  }
}

Expected SQL

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

Tried Dynamic Linq :

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

Returns Exception :

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

Dependicies :

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

回答1:

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

When translating to the dynamic query you have mixed the variable names, because i and j are too similar.
it is ambigous as there are 2 lambdas and so it is parsed as a parameter of the innermost lambda.

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();

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();

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

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

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

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();

Or like this:

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

来源：https://stackoverflow.com/questions/57624006/multiple-values-contains-with-dynamic-linq

标签

linq

.net-core

dynamic-linq