perform LIKE search with entity framework and npgsql

Question

How can I perform a LIKE search with entity framework 6 and npgsql?

I tried

1. SQLMethods.Like

queryable.Where(entity => SqlMethods.Like(entity.Name, "%EW%6%"));

but I got the message

LINQ to Entities does not recognize the method 'Boolean Like(System.String, System.String)' method, and this method cannot be translated into a store expression.

2. linq extension method

Then I tried the linq extension method WhereLike from this stackoverflow post: https://stackoverflow.com/a/27153779/1489968

It's working, but not for all cases, because it's cutting the search string into several pieces.

queryable.WhereLike(t => t.Name, "%EW%6%"));

is transformed into two and-connected Contains calls, that are transformed into two LIKE expressions.

SELECT ... 
WHERE ... AND 
("Extent1"."name" LIKE E'%EU%' AND "Extent1"."name" LIKE E'%6%')

which means "All entities with the name containing 'EU' and '6'"

But I want the transformation to result in a query like the following one:

SELECT ... 
WHERE ... AND
("Extent1"."name" LIKE E'%EW%6%')

which means "All entities with the name containing 'EU' followed by a string, that contains '6'"

Answer 1

You can achieve the same goal using Regex.IsMatch().

Eg one of the unit tests from Npgql repository :

[Fact]
public virtual void Regex_IsMatchOptionsNone()
{
    AssertQuery<Customer>(
        cs => cs.Where(c => Regex.IsMatch(c.CompanyName, "^A", RegexOptions.None)),
        entryCount: 4);
    Assert.Contains("WHERE \"c\".\"CompanyName\" ~ ('(?p)' || '^A')", Sql);
}

So I believe in your case it would look something like this:

var pattern = ".*" + Regex.Escape("EW") + ".*" + Regex.Escape("6") + ".*";
queryable.Where(t => Regex.IsMatch(t.Name, pattern));