LINQ to SQL where clause verifying string contains list element

Question

I'm using a view returning Domains according to an id. The Domains column can be 'Geography' or can be stuffed domains 'Geography,History'. (In any way, the data returned is a VARCHAR)

In my C# code, I have a list containing main domains:

private static List<string> _mainDomains = new List<string>()
{
    "Geography",
    "Mathematics",
    "English"
};

I want to filter my LINQ query in order to return only data related to one or many main Domain:

expression = i => _mainDomains.Any(s => i.Domains.Contains(s));
var results = (from v_lq in context.my_view
                select v_lq).Where(expression)

The problem is I can't use the Any key word, nor the Exists keyword, since they aren't available in SQL. I've seen many solutions using the Contains keyword, but it doesn't fit to my problem.

What should I do?

Answer 1

I figured it out. Since I can't use the Any keyword, I used this function:

    public static bool ContainsAny(this string databaseString, List<string> stringList)
    {
        if (databaseString == null)
        {
            return false;
        }
        foreach (string s in stringList)
        {
            if (databaseString.Contains(s))
            {
                return true;
            }
        }
        return false;
    }

So then I can use this expression in my Where clause:

expression = i => i.Domains.ContainsAny(_mainDomains);

Update: According to usr, the query would return all the values and execute the where clause server side. A better solution would be to use a different approach (and not use stuffed/comma-separated values)

Answer 2

You can use contains:

where i.Domains.Any(s => _mainDomains.Contains<string>(s.xxx))

Notice that the generic arguments are required (even if Resharper might tell you they are not). They are required to select Enumerable.Contains, not List.Contains. The latter one is not translatable (which I consider an error in the L2S product design).

(I might not have gotten the query exactly right for your data model. Please just adapt it to your needs).