mscrm queryexpression在unittest中返回空值

我正在尝试返回第一个在值中有值的实体。唯一可以测试它的方法是通过单元测试,每次都失败,因为它返回空值。不是空的EntityCollection,而是空的。我在这里做错什么了。我就是看不见?EC=空,并在尝试获取FirstOrDefault时引发错误

QueryExpression query = new QueryExpression()
{
    EntityName = "myentity",
    ColumnSet = new ColumnSet(true),
    Criteria = new FilterExpression
    {
        FilterOperator = LogicalOperator.And,
        Conditions = 
        {
            new ConditionExpression("myattribute", ConditionOperator.Like, "%" +somevalue+ "%")
        }
    }
};

EntityCollection ec = service.RetrieveMultiple(query);
return ec.Entities.FirstOrDefault();