Question

我的名单是＆＃34; listA＆＃34;包含1个名为＆＃34; fieldA＆＃34;和数据是

{1,0,0,0,1}

我想检测＆＃34; 1＆＃34;是否存在重复？只是，但如果＆＃34; 0＆＃34;重复，它不会被视为重复

我试试

 var dupl = listA
                            .GroupBy(i => i.fieldA=="1")
                            .Where(g => g.Count() > 1)
                            .Select(g => g.Key).ToList();
 if (dupl.Count()>0){"you have duplicated 1"}

但＆＃34; 0＆＃34;仍被检测为重复，我的linq出了什么问题？

Answer 1

如果您只想知道是否有重复的1，那么只需使用Count：

bool isDuplicate = listA.Count(x => x.fieldA == "1") > 1;

Answer 2

你可以尝试这个：

bool oneIsDuplicate = listA.Where(x=>x.fieldA=="1").Count() > 1;

Answer 3

这个可能会有所帮助。在达到集合结束之前满足条件时，我们避免了额外的迭代。（如果在集合结束之前满足条件，我们不会迭代整个集合，因此它会更多一些明智地调整了表现）。

public static class Extentions
    {
        /// <summary>
        /// Used to find if an local variable aggreation based condition is met in a collection of items.
        /// </summary>
        /// <typeparam name="TItem">Collection items' type.</typeparam>
        /// <typeparam name="TLocal">Local variable's type.</typeparam>
        /// <param name="source">Inspected collection of items.</param>
        /// <param name="initializeLocalVar">Returns local variale initial value.</param>
        /// <param name="changeSeed">Returns desired local variable after each iteration.</param>
        /// <param name="stopCondition">Prediate to stop the method execution if collection hasn't reached last item.</param>
        /// <returns>Was stop condition reached before last item in collection was reached.</returns>
        /// <example> 
        ///  var numbers = new []{1,2,3};
        ///  bool isConditionMet = numbers.CheckForLocalVarAggreatedCondition(
        ///                                             () => 0, // init
        ///                                             (a, i) => i == 1 ? ++a : a, // change local var if condition is met 
        ///                                             (a) => a > 1);   
        /// </example>
        public static bool CheckForLocalVarAggreatedCondition<TItem, TLocal>(
                                this IEnumerable<TItem> source,
                                Func<TLocal> initializeLocalVar,
                                Func<TLocal, TItem, TLocal> changeSeed,
                                Func<TLocal, bool> stopCondition)
        {
            TLocal local = default(TLocal);
            foreach (TItem item in source)
            {
                local = changeSeed(local, item);
                if (stopCondition(local))
                {
                    return true;
                }
            }

            return false;
        }
    }

在列表C＃中搜索特定的重复键

3 个答案: