c＃当我尝试在我的列表中调试console.write元素时，如何修复foreach <string>

Question

I am learning c# and i have some problem with my code. I have no idea why i cant use foreach in my example . What can i do to fix this problem? Any suggestions?

  public class Company
  {
    List<string> workers;
    public Company()
    {
        workers= new List<string>();
    }
    public void AddWorker(string x)
    {
        workers.Add(x);
    }
  }

    static void Main(string[] args)
    {
        Company c1= new Company();
        c1.AddWorker("Adam Snow");
        c1.AddWorker("John Big");
        c1.AddWorker("Chris Zen");

        foreach (var x in c1)
        {
            Console.WriteLine(x);
        }
     }

Answer 1

In the line

foreach (var x in c1)

you try to iterate over your instance of Company which is not enumerable. You want to iterate over the workers list of that instance.

One solution is to make workers a public property:

public class Company
{
    List<string> workers;
    public IEnumerable<string> Workers { get { return workers; } }

    // shortened for brevity
}

and then you can use foreach like that:

foreach (var x in c1.Workers) // <- access the Workers property here
{
    Console.WriteLine(x);
}

---

As Dmitry suggested, you may want to expose the workers list only as readonly, so that users of that class cannot change the list's content from outside:

public class Company
{
    List<string> workers;
    public IReadOnlyCollection<string> Workers
    { 
        get { return workers.AsReadOnly(); }
    }

    // shortened for brevity
}

Answer 2

If you want iterate over Company class instance, Company has to implement IEnumerable<string> :

public class Company : IEnumerable<string>{
  ...
  public IEnumerator<string> GetEnumerator() {
    return workers.GetEnumerator();
  }

  IEnumerator IEnumerable.GetEnumerator() {
    return workers.GetEnumerator();
  }
}

having done this you can put

Company c1 = new Company();

foreach (var x in c1) {
  Console.WriteLine(x);
}

Answer 3

do workers list public and loop in c1.workers then it's ok.

public List<string> workers;

then

foreach (var x in c1.workers)
{
    Console.WriteLine(x);
}