Question

我正在尝试从object[]列表中检索ID列表。这是我的代码：

private static List<int> getReceivedIds(object[] objectList)
{
    var received = new List<int>();
    foreach (object[] b in objectList)
    {
        if (b != null)
        {
            received.Add(int.Parse((b[0].ToString())));
        }
    }
   return received;
}

我正在为此代码寻找性能优化的解决方案。

我将代码更改为：

    private static List<int> getReceivedIds2(object[] objectList)
    {
        var received = new List<int>();
        foreach (object[] b in objectList)
        {
            if (b != null)
            {
                received.Add((int)b[0]);
            }
        }
        return received;
    }

我还比较了LINQ查询和foreach语句性能，结果如下： Performance test results

测试显示foreach语句比LINQ快6倍。

任何人都可以提高此代码的性能吗？

以下是我测试的代码：

class Program
{
    static void Main(string[] args)
    {
        for (int test = 0; test < 100; test++)
        {
            object[] objectList = new object[1000];
            Random rnd = new Random();
            for (int i = 0; i < 1000; i++)
            {
                objectList[i] = new object[] { rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000) };
            }
            Stopwatch stopWatch = new Stopwatch();
            stopWatch.Start();
            for (int i = 1; i < 100000; i++)
            {
                getReceivedIds(objectList);
            }
            stopWatch.Stop();
            var t1 = stopWatch.Elapsed.TotalMilliseconds;

            stopWatch.Restart();
            for (int i = 1; i < 100000; i++)
            {
                getReceivedIds2(objectList);
            }
            stopWatch.Stop();
            var t2 = stopWatch.Elapsed.TotalMilliseconds;

            Console.WriteLine(string.Format("LINQ: {0}  -  ForEach: {1}", t1, t2));
        }
    }


    private static List<int> getReceivedIds(object[] objectList)
    {
        List<int> received = objectList.Cast<object[]>()
        .Where(b => b != null)
        .Select(b => (int)b[0])  // or Convert.ToInt32(b[0])
        .ToList();
        return received;
    }

    private static List<int> getReceivedIds2(object[] objectList)
    {
        var received = new List<int>();
        foreach (object[] b in objectList)
        {
            if (b != null)
            {
                received.Add((int)b[0]);
            }
        }
        return received;
    }
}

Answer 1

如果object[]中的第一项实际上是int，您不需要解析它，您可以投出它。如果需要，可以使用此LINQ查询：

List<int> received = objectList.Cast<object[]>()
    .Where(b => b != null)
    .Select(b => (int)b[0])  // or Convert.ToInt32(b[0])
    .ToList();

Answer 2

试试这个：

 int[] resultArray = Array.ConvertAll(inputArray, x => Convert.ToInt32(x));

注意：确保值为int。
供参考：msdn link for ConvertAll()

从c＃

2 个答案: