對List進行查詢的時候，會有多種方法供我們使用，但是在追求程式碼簡潔和效率的情況下，哪種方法才是我們的最優選擇呢？

先把我的測試結果擺出了吧~

測試結果

for的效率是最高的，但是再兼顧行數和效率的情況下首選Find

測試內容

1.計算程式的執行時間

    //用Stopwatch類(System.Diagnostics
 
)計算耗時
    static void SubTest()  
    {  
        Stopwatch sw = new Stopwatch();  
        sw.Start();  

        //耗時巨大的程式碼  

        sw.Stop();  
        TimeSpan ts2 = sw.Elapsed;  
        Console.WriteLine("Stopwatch總共花費{0}ms.", ts2.TotalMilliseconds);  
    }  

2.測試List

 public class model
 {
      public
 
 string name { set; get; }
      public int age { set; get; }
 }
 List<model> list=new List<model>();

List查詢方法

• for

int myage ;
for (int i = 0; i < list.Count; i++)
{
    if (list[i].name == "小明") myage = list[i].age;
}

• foreach

int myage ;
foreach(model m in
 
 list)
{
     if(m.name=="小明") myage = m.age;
}

• Find

int myage = list.Find(x => x.name == "小明").age;

• FirstOrDefault

int myage = list.FirstOrDefault(s => s.name == "小明").age;

完整程式碼

public partial class Form1 : Form
    {
        List<model> list;
        model p1,p2;
        /// <summary>
        /// for的方式查詢
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button1_Click(object sender, EventArgs e)
        {
            int count = 0;
            int myage;
            Stopwatch sw = new Stopwatch();
            sw.Start();
            while (count < 100000)//計算迴圈100000次的耗時
            {
                for (int i = 0; i < list.Count; i++)
                {
                    if (list[i].name == "小明")myage = list[i].age;
                }
                count++;
            }
            sw.Stop();
            TimeSpan ts2 = sw.Elapsed;
            Console.WriteLine("Stopwatch總共花費{0}ms.", ts2.TotalMilliseconds);
        }

        /// <summary>
        /// foreach的方式查詢
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button2_Click(object sender, EventArgs e)
        {
            int count = 0;
            int myage;
            Stopwatch sw = new Stopwatch();
            sw.Start();
            while (count < 100000)
            {
                foreach(model m in list)
                {
                    if(m.name=="小明") myage = m.age;
                }
                count++;
            }                      
            sw.Stop();
            TimeSpan ts2 = sw.Elapsed;
            Console.WriteLine("Stopwatch總共花費{0}ms.", ts2.TotalMilliseconds);
        }

        /// <summary>
        /// Find的方式查詢
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button3_Click(object sender, EventArgs e)
        {
            int count = 0;
            int myint;
            Stopwatch sw = new Stopwatch();
            sw.Start();
            while (count < 100000)
            {
                myint = list.Find(x => x.name == "小明").age;
                count++;
            }
            sw.Stop();
            TimeSpan ts2 = sw.Elapsed;
            Console.WriteLine("Stopwatch總共花費{0}ms.", ts2.TotalMilliseconds);
        }

        /// <summary>
        /// FirstOrDefault的方式查詢
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button4_Click(object sender, EventArgs e)
        {
            int count=0;
            int myage;
            Stopwatch sw = new Stopwatch();
            sw.Start();
            while (count < 100000)
            {
                myage = list.FirstOrDefault(s => s.name == "小明").age;
                count++;
            }
            sw.Stop();
            TimeSpan ts2 = sw.Elapsed;
            Console.WriteLine("Stopwatch總共花費{0}ms.", ts2.TotalMilliseconds);
        }
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            p1 = new model();
            p1.name = "小紅";
            p1.age = 10;
            p2 = new model();
            p2.name = "小明";
            p2.age = 23;
            list = new List<model>();
            list.Add(p1);
            list.Add(p2);
        }

    }
    public class model
    {
        public string name { set; get; }
        public int age { set; get; }
    }