获取错误＆＃34;值不能为NULL＆＃34;在运行LINQ查询时

Question

我正在运行下面的LINQ to Entities查询，它崩溃时出现错误{"Value cannot be null.\r\nParameter name: outer"}

    foreach (ProviderAddresses pa in providerAddresseses)
    {
        var eaAddrs = (from addrs in this.Context.EaAddresseses
            join ea in this.Context.EntityAssignments
                on addrs.Ea_K equals ea.Ea_K
            where addrs.ProviderAddress_K == pa.ProviderAddress_K
            select new
            {
                EAAddress = addrs,
                AssignmentRTK = ea.Assignment_RTK
            });

但是我传递的参数并不是真的，所以导致这个的原因是什么？是因为我传递一个List对象并加入LINQ to Entities中的真实表吗？他们不一起工作？