Yield and generics rock! - Tales from the Evil Empire - The Diigo Meta page

• 15 May 08
  

  Tad Donaghe

  .net yield generics

• 14 May 08
  

  Lindsay Donaghe

  How to create a filter for generic lists (or other IEnumerable objects) without creating a temporary list first. Illustrates how to use the yield statement as well and create your own generic enumerator.

  C# .Net codesnippets development generics

  • public sealed class FilteredEnumerable<T> : IEnumerable<T>, IEnumerable {
    
      private IEnumerable<T> _enumerable;
      private Predicate<T> _filter;
    
      public FilteredEnumerable(IEnumerable<T> enumerable, Predicate<T> filter) : base() {
        _enumerable = enumerable;
        _filter = filter;
      }
    
      IEnumerator<T> IEnumerable<T>.GetEnumerator() {
        foreach (T item in _enumerable) {
          if (_filter == null || _filter(item)) {
            yield return item;
          }
        }
      }
    
      IEnumerator IEnumerable.GetEnumerator() {
        return (IEnumerator)(((IEnumerable<T>)this).GetEnumerator());
      }
    }
  • string[] stringsToFilter = new string[] {"Red", "Green", "Blue", "Pink"};
    Predicate<string> filter = delegate(string stringToFilter) {
      return (stringToFilter.IndexOf('e') != -1);
    };
    filteredStrings = new FilteredEnumerable<string>(stringsToFilter, filter);

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