c# – 像IList.IndexOf()中的东西,但是在IEnumerable？

因此,LINQ没有IndexOf方法.

但是,您可以自己写一个：

///<summary>Finds the index of the first item matching an expression in an enumerable.</summary>
///<param name="items">The enumerable to search.</param>
///<param name="predicate">The expression to test the items against.</param>
///<returns>The index of the first matching item,or -1 if no items match.</returns>
public static int FindIndex<T>(this IEnumerable<T> items,Func<T,bool> predicate) {
    if (items == null) throw new ArgumentNullException("items");
    if (predicate == null) throw new ArgumentNullException("predicate");

    int retVal = 0;
    foreach (var item in items) {
        if (predicate(item)) return retVal;
        retVal++;
    }
    return -1;
}
///<summary>Finds the index of the first occurence of an item in an enumerable.</summary>
///<param name="items">The enumerable to search.</param>
///<param name="item">The item to find.</param>
///<returns>The index of the first matching item,or -1 if the item was not found.</returns>
public static int IndexOf<T>(this IEnumerable<T> items,T item) { return items.FindIndex(i => EqualityComparer<T>.Default.Equals(item,i)); }