C# 判断字符为空的6种方法的效率实测对比

本文主要介绍了C#中判断字符是否为空的方法，并实测对比各种方法的执行效率，最后推荐大家使用IsNullOrEmpty，效率和易用性比较均衡。  

C#中提供了相当丰富的方法或属性来判断一个字符是否为空，常用的方法有以下6种

1. strTest== ""

2. strTest.Equals("")

3. strTest== string.Empty

4. strTest.Equals(string.Empty)

5. strTest.Length == 0

6. string.IsNullOrEmpty(strTest)

为了对以上6种方法的效率，有个直观的感受，我特意编写了以下的测试代码：

using System;

namespace StrTest
{
  class Program
  {
    //定义3个字符串 以便测试在多种情况下 下面6种判断方法的速度
    public static string strTest01 = "";
    public static string strTest02 = string.Empty;
    public static string strTest03 = "0123456789";

    public static DateTime start, end; //定义开始时间 和 结束时间
    public static TimeSpan ts;    //定义两个时间的间隔

    //**********************对strTest使用6种测试方法*****************************
    public static void Test(string strTest)
    {
      //string == ""
      start = DateTime.Now;
      for (int counter = 0; counter <= 100000000; counter++)
      {
        if (strTest == "")
        {
        }
      }
      end = DateTime.Now;
      ts = end - start;
      Console.WriteLine("string == /"/" 时间消耗为 " + ts.TotalSeconds + " 秒");

      //string.Equals("")
      start = DateTime.Now;
      for (int counter = 0; counter <= 100000000; counter++)
      {
        if (strTest.Equals(""))
        {
        }
      }
      end = DateTime.Now;
      ts = end - start;
      Console.WriteLine("string.Equals(/"/") 时间消耗为 " + ts.TotalSeconds + " 秒");

      //string == stirng.Empty
      start = DateTime.Now;
      for (int counter = 0; counter <= 100000000; counter++)
      {
        if (strTest == string.Empty)
        {
        }
      }
      end = DateTime.Now;
      ts = end - start;
      Console.WriteLine("string == string.Empty 时间消耗为 " + ts.TotalSeconds + " 秒");

      //string.Equals(string.Empty)
      start = DateTime.Now;
      for (int counter = 0; counter <= 100000000; counter++)
      {
        if (strTest.Equals(string.Empty))
        {
        }
      }
      end = DateTime.Now;
      ts = end - start;
      Console.WriteLine("string.Equals(string.Empty) 时间消耗为 " + ts.TotalSeconds + " 秒");

      //string.Length == 0
      start = DateTime.Now;
      for (int counter = 0; counter <= 100000000; counter++)
      {
        if (strTest.Length == 0)
        {
        }
      }
      end = DateTime.Now;
      ts = end - start;
      Console.WriteLine("string.Length == 0 时间消耗为 " + ts.TotalSeconds + " 秒");

      //string.IsNullOrEmpty(string)
      start = DateTime.Now;
      for (int counter = 0; counter <= 100000000; counter++)
      {
        if (string.IsNullOrEmpty(strTest))
        {
        }
      }
      end = DateTime.Now;
      ts = end - start;
      Console.WriteLine("string.IsNullOrEmpty(string) 时间消耗为 " + ts.TotalSeconds + " 秒" + "/n");
    }

    static void Main(string[] args)
    {
      Console.WriteLine("=======================================");
      Console.WriteLine("strTest = /"/" 的5种测试结果");     
      Console.WriteLine("=======================================");

      Test(strTest01);

      Console.WriteLine("=======================================");
      Console.WriteLine("strTest = string.Emtpy 的5种测试结果"); 
      Console.WriteLine("=======================================");

      Test(strTest02);

      Console.WriteLine("=======================================");
      Console.WriteLine("strTest = /"0123456789/" 的5种测试结果"); 
      Console.WriteLine("=======================================");

      Test(strTest03);

      Console.ReadLine();  //等待键盘的输入 作用:使屏幕暂停在此处
    }
  }
}								 
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