Using contains() in LINQ to SQL

Question

I\'m trying to implement a very basic keyword search in an application using linq-to-sql. My search terms are in an array of strings, each array item being one word, and I

Answer 1

A simpler and more correct solution (then leppie's):

public IQueryable SearchForParts(string[] query)
{
    var q = db.Parts.AsQueryable(); 

    foreach (string qs in query)
    {
        q = q.Where(x => x.partName.Contains(qs));
    }

    return q;
}

This will work as long as partName is a string (or an SQL equivalent of a string).

The important thing to note is partName.Contains(qs) is different than query.Contains(partName).
With partName.Contains(qs), partName is searched for any occurrence of qs. The resulting SQL would be equivalent (where is the value of qs):

select * from Parts where partName like '%%';

Also of note are StartsWith and EndsWith which are similar to Contains but look for the string in the specific location.

query.Contains(partName) is the same as a SQL in command. The resulting SQL would be equivalent to (where is the value of query[0], is the value of query[1], and is the last value in the query array):

select * from Parts where partName in ( , , ...,  );

Update:
It is also important to note that leppie's answer does not escape the wildcard characters before adding them to the like statement. This is not an issue with the Contains solution since Linq will escape the query before sending it. An escaped version of the SqlMethods.Like solution would be:

public IQueryable SearchForParts(string[] query)
{
    var q = db.Parts.AsQueryable(); 

    foreach (var qs in query)
    {
        string escaped_bs = qs.Replace("/", "//"),
            escaped_us = escaped_bs.Replace("_", "/_"),
            escaped_p = escaped_us.Replace("%", "/%"),
            escaped_br = escaped_p.Replace("[", "/["),
            likestr = string.Format("%{0}%", escaped_br);

        q = q.Where(x => SqlMethods.Like(x.partName, likestr, '/'));
    }

    return q;
}

You don't have to worry about ' since Linq will escape that for you.