在IEnumerable中是否有任何方法/扩展方法,允许我找到一个对象实例的索引？像IList中的IndexOf()？
indexPosition = myEnumerable.IndexOf() ?
谢谢
解决方法
IEnumerable不是有序集.
虽然大多数IEnumerables都是有序的,但有些(如Dictionary或HashSet)不是.
虽然大多数IEnumerables都是有序的,但有些(如Dictionary或HashSet)不是.
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)); }
