三种常用的字符串判空串方法执行速度比较

三种常用的字符串判空串方法：
　　　1: bool isEmpty = (str.Length == 0);
　　　2: bool isEmpty = (str == String.Empty);
　　　3: bool isEmpty = (str == "");
　　哪种方法最快？

以下是测试代码：

using System;
public class strLengthTime
{
       public static void Main()
{
string strTest = "";
string strSub;
for (int i = 0; i < 1000; i++)
{
       strSub = i.ToString();
       strTest = strTest + strSub;
}
DateTime startTime;
DateTime endTime;
TimeSpan timeCost;
startTime = DateTime.Now;
for (int m = 0; m < 100000000; m++)
{
       if (strTest.Length == 0)
{
}
}

endTime = DateTime.Now;
timeCost = endTime - startTime;
System.Console.WriteLine("strTest.Length Method Costs:" + timeCost.TotalMilliseconds.ToString());
startTime = DateTime.Now;
for (int m = 0; m < 100000000; m++)
{
         if (strTest == string.Empty)
{
}
}
endTime = DateTime.Now;
timeCost = endTime - startTime;
System.Console.WriteLine("String.Empty Method Costs:" + timeCost.TotalMilliseconds.ToString());
startTime = DateTime.Now;
for (int m = 0; m < 100000000; m++)
{
            if (strTest == "")
{
}
}
endTime = DateTime.Now;
timeCost = endTime - startTime;
System.Console.WriteLine("The Third Method Costs:" + timeCost.TotalMilliseconds.ToString());
Console.ReadLine();
}
}

执行结果：

string.Length==0方法的速度最快。

于是在今后的比较空串的时候，请多用 string.Length==0。