我怎么能叫从一个LINQ EX pression的方法？ [英] How can I call a method from within a LINQ expression?

问题描述

我有我的模型的东西，也许是这样的：

I've my Model something maybe like this :

    public class Person
    {
        public virtual Guid ID { get; set; }
        public virtual string FirstName { get; set; }
        public virtual string LastName { get; set; }
        //this LazyList takes IQueryable<T> in constructor
        public virtual LazyList<Role> Roles { get; set; }

        //this method to convert the object that comes from EF to my own model
        public static Person FromData(DBPerson dbPerson)
        {
            if (dbPerson != null)
                return new Person
                {
                    ID = dbPerson.ID,
                    FirstName = dbPerson.FirstName,
                    LastName = dbPerson.LastName,
                };

            return null;
        }
     }

然后在我的仓库我有方法让所有的人，但我需要它给了 LazyList＆LT;作用＆GT; 属性将导致其他私有方法getRoles。 我的资料库看起来是这样的：

Then in my Repository I've method to get all persons but i need it to give to the LazyList<Role> property result from other private method "getRoles". My repository looks like this:

        public IQueryable<Person> GetPersons()
        {
            var list = from dbPerson in context.Persons 
                       select Person.FromData(dbPerson);
       // Here is the problem :(
            return list;
        }

        private LazyList<Role> getRoles(GUID userID)
        {
            var list = from role in db.Roles
                       where role.UserID == userID
                       select role.ToModel();

            return new LazyList<Role>(list);
        }

我想要的东西，在这里告诉大家，我想Person.Roles从getRoles法

也许会有人告诉我将转换dbPerson我的人在仓库的逻辑，然后把这样的事情：

Maybe someone will tell me to put the logic of converting the dbPerson to my Person in the repository and then put something like this :

        public IQueryable<Person> GetPersons()
        {
            var list = from dbPerson in context.Persons 
                       select new Person{
                    ID = dbPerson.ID,
                    FirstName = dbPerson.FirstName,
                    LastName = dbPerson.LastName,
                    Roles = getRoles(dbPerson.ID)};
        }

确定，将工作，但我真的需要把转换dbPerson到我的模型在不同的方法，因为我就告了很多次，我的解决方案的逻辑。

OK that will work but i really need to put the logic of converting dbPerson to my model in separate method because i'll sue it many times in my solution.

那么怎么办呢？

推荐答案

我意识到，我不能只是以前叫我特殊的方法调用任何外部方法，直到我的GetEnumerator。  而这个错误是提出的实体框架。

I realized that i can't call any external method until i GetEnumerator just before calling my special method. And this error is raised by Entity Framework.

所以，code应该是这样的：

        public IQueryable<Person> GetPersons()
        {
            var list = context.Persons.select(p=>p).AsEnumerable()
                      .Select(m=>m.MyExtensionMethod());
            return list;
        }

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