How can I parse a string into a UNIQUEIDENTIFIER?

I'm writing an Entity Framework LINQ query in which I want to parse a string into a UNIQUEIDENTIFIER (aka GUID) as part of the WHERE clause:

public IEnumerable<User> Find(Guid guid)
{
    return dbContext
        .Users
        .Where(user => Guid.Parse(user.GuidText) == guid);
}

I know this is possible in SQL because I've tested it:

SELECT *
FROM Users
WHERE CAST(GuidText AS UNIQUEIDENTIFIER) = @guid;

However, I haven't found a way to generate the CAST part. I've tried:

1. (Guid)user.GuidText, which generates a compiler error.
2. Convert.ToGuid(user.GuidText), but this method doesn't exist.
3. Guid.Parse(user.GuidText), but this causes Entity Framework to generate an error when it translates the LINQ query.
4. new Guid(user.GuidText), but this causes Entity Framework to generate an error when it translates the LINQ query.
5. (Guid)Convert.ChangeType(user.GuidText, typeof(Guid)), but this causes Entity Framework to generate an error when it translates the LINQ query.
6. SqlGuid.Parse(user.GuidText), but this causes Entity Framework to generate an error when it translates the LINQ query.

How can I achieve this? I'm willing to embed SQL in the code as a last resort.