Appending my query in LINQ to SQL

I'm trying to build my l2s query based on the existence of a parameter. I am able to achieve this for direct properties of my object, but when one of the properties is a many -> many entity, I'm unable to figure it out.

For example, my user table has a name column.

There is also a brand table and a user may have multiple brands as stored in the brand_users table.

I want to append to my query a condition that will query only users that have 开发者_如何学JAVAan entry in the brand_users table with a specific brandid.

GetUser(UserSearchParameter searchParam)
{
    var query = from u in Users select u;

    if(searchParam.Name != null)
        query = query.Where(u => u.Name.Contains(searchParam.Status)); // this works!!

    if(searchParam.BrandId != null)
        query = query.Where??? // this is where I'm stuck

    return new List<user>(query);
}

How about:

query = query.Where(u => Brands.Any(brand => brand.UserId == u.UserId &&
                                          brand.BrandId == searchparam.brandId));

It's hard to give more detail without knowing the structure of your brands table though, or how it's represented in LINQ to SQL.

Something like

query = query.Where(u => u.Brand_Users.Any());

Assuming you've mapped the brand_users many->many table in a L2S relationship, with the name as above.