IEnumerable - implementing using GetEnumerator from local variable

问题

I'm newb with generics/iterators/enumerators etc.

I have code, it keeps field number (int) and error mesages (List string) for each field:

  public class ErrorList : IEnumerable // ?
  {
        private Dictionary <int, List<string>> errorList;

        // ...
  }

How to make this class work with foreach loop? I wanna use GetEnumerator form Dictionary, but how should i do this?

回答1:

You could simply provide a public GetEnumerator method:

public class ErrorList
{
    private Dictionary<int, List<string>> errorList = new Dictionary<int, List<string>>();

    ... some methods that fill the errorList field

    public IEnumerator<KeyValuePair<int, List<string>>> GetEnumerator()
    {
        return errorList.GetEnumerator();
    }
}

and now assuming you have an instance of ErrorList:

var errors = new ErrorList();

you can loop through them:

foreach (KeyValuePair<int, List<string>> item in errors)
{
    ...
}

回答2:

Dictionary implements IEnumerable<KeyValuePair<TKey, TValue>>, so this works:

foreach (KeyValuePair<Int, List<String>> kvp in errorList) {
    var idx = kvp.Key;
    var vals = kvp.Value;
    // ... do whatever here
}

回答3:

You can simply return errorList.GetEnumerator().

来源：https://stackoverflow.com/questions/9844159/ienumerable-implementing-using-getenumerator-from-local-variable