试试这个

using(var ctx = new Dbcontext()) 
{
    var list = (
        from cs in ctx.CLIENTSSUITS
        join trust in ctx.TRUSTS on cs.CLIENT equals trust.CLIENT
        join at in ctx.ADV_TYPES on at.CODE equals trust.AT into temp from temp.DefaultIfEmpty()
        join tla1 in ctx.CLIENTADDRESSES on tla.SSN equals trust.SSN && tla.ID = 'L' into temp2 from subtla1 in temp2.DefaultIfEmpty()
        join tla2 in ctx.CLIENTADDRESSES on tla2.SSN equals trust.SSN && tla2.ID = 'M' into temp3 from subtla2 in temp3.DefaultIfEmpty()             
        where (cs.PRIMARY = w && ?.SecondaryRole = x && cs.ID = y && cs.Rev = z && cs.DELETED = 0)
        select new
        {
        FName = trust.FName,
        MName = trust.MName,
        LName = trust.LName
        LAddress = tla.Address,
        MAddress = tma.Address,
        Descr = at.Descr
        }).ToList();
}

    //if the list contains the right result then you can easily group it with this code

    var results = list.GroupBy(x => new {
     x.FName, x.MName, x.LName, x.LAddress, x.MAddress, Descr
    });