cast from List<EntityObject> to EntityObject

My code is as below.

public void CreateNewAuthor(List<Author> ne开发者_Python百科wAuthor)
{
    publishContext.AddToAuthors(newAuthor);
}

I know this will result in error as AddToAuthors(Author newAuthor) accepts entity object as parameter while I am passing a List<>. So how this should be handled? How to cast a List<> to entity object before AddToAuthors()?

---

You're accepting multiple authors - but you're trying to call something which takes a single author. Are you expecting multiple values within your list, or just a single one?

It sounds like you might just want to loop:

public void CreateNewAuthor(List<Author> newAuthors)
{
    foreach (Author newAuthor in newAuthors)
    {
        publishContext.AddToAuthors(newAuthor);
    }
}

... or it's entirely possible that the context already provides a way of adding multiple authors at a time. (I'm not an EF person, so I don't know for sure.)

The important thing is that you understand the possibilities here - the list could contain no authors, one author or multiple authors. Are all of those valid in your code? How do you want to handle each of those situations?

---

You could loop trough the list and add all the Author objects this list contains:

foreach (Author author in newAuthor)
{
    publishContext.AddToAuthors(author);
}

---

Case 1. You know that the list contains only one item:

1. Change your method's signature to the following:

   public void CreateNewAuthor(Author newAuthor)
   

   (It is very unintuitive to refer to a list of items with a name that is not in the plural. It is even more unintuitive that your method accepts a list of (ie. "several") Author objects, yet requires that the list contain only one item.)

2. Then, call your method as follows:

   // using System.Linq;
   // List<Author> someListOfAuthors = new List<Author> { someAuthor };
   CreateNewAuthor( someListOfAuthors.Single() );
   

   or, without using LINQ:

   CreateNewAuthor( someListOfAuthors[0] );
   

Case 2. The list may contain any number of items:

1. Rename the parameter from newAuthor to newAuthors, for the same reason mentioned above.

2. Change your method body to this:

   foreach (Author author in newAuthors)
   {
       publishContext.AddToAuthors(author);
   }