C#/ListIndexOf.cs

   1 using System;
   2 using System.Collections.Generic;
   3
   4 namespace IEnumerableExtras
   5 {
   6     public static class ListIndexOf
   7     {
   8         /// <summary>
   9         /// Return index of first element of this list satisfying filter function or -1.
  10         /// </summary>
  11         /// <typeparam name="T"></typeparam>
  12         /// <param name="list"></param>
  13         /// <param name="filterFunc"></param>
  14         /// <returns></returns>
  15         public static int IndexOf< T >( this IList<T> list, Func<T, bool> filterFunc )
  16         {
  17             return IndexOf( list, filterFunc, 1 );
  18         }
  19
  20         /// <summary>
  21         /// Return index of first element of this list satisfying filter function or -1.
  22         /// </summary>
  23         /// <typeparam name="T"></typeparam>
  24         /// <param name="list"></param>
  25         /// <param name="quant">Quntifier, index will be divisible by this number</param>
  26         /// <param name="filterFunc"></param>
  27         /// <returns></returns>
  28         public static int IndexOf< T >( this IList<T> list, Func<T, bool> filterFunc, int quant )
  29         {
  30             if ( quant <= 0 )
  31             {
  32                 throw new ArgumentException( "Qunatifier must be greater than zero.", "quant" );
  33             }
  34
  35             int index = -1;
  36             for ( int i = 0; i < list.Count; i += quant )
  37             {
  38                 if ( filterFunc( list[ i ] ) )
  39                 {
  40                     index = i;
  41                     break;
  42                 }
  43             }
  44
  45             return index;
  46         }
  47     }
  48 }