Linq - Simulate an OrWhere expression when building LINQ queries dynamically?

Question

The code snippet below search allow the user to match a string against three fields in the table. If any of the fields match, the entry is included in the result. However, u

Answer 1

Not exactly pretty, but it would work.

var foundUsers = entities.UserInfo.Where(u =>
    (searchCompleteName && u.CompleteName.Contains(searchString))
    || (searchPortalID && u.PortalID.Contains(searchString))
    || (searchUsername && u.UserIdentity.Contains(searchString));

You could also do this with a union. The union operator returns distinct results so there will not be any duplicates. I have no idea if EF can defer this to the database.

var foundUsers = Enumerable.Empty().AsQueryable();

if (searchCompleteName)
{
    foundUsers = foundUsers.Union(entities.UserInfo.Where(u => u.CompleteName.Contains(searchString)));
}

if (searchPortalID)
{
     foundUsers = foundUsers.Union(entities.UserInfo.Where(u => u.PortalID.Contains(searchString)));
}

if (searchUsername)
{
     foundUsers = foundUsers.Union(entities.UserInfo.Where(u => u.PortalID.Contains(searchString)));
}