Empty string comparison : Performance Calls

String comparison is one most frequent we do while coding, especially, comparison with emtpy string.For a string TestString, We tend to do it in mainly 3 ways
1. if(TestString == "")
2. if(TestString == string.Empty)
3. if(TestlLength == 0)

DateTime time = DateTime.Now;
string TestString = "";
for(int i =0;i<10000000;i++)
{
if(TestString.Length == 0)
if(TestString == "")
{
}
}
double TimeTaken = (DateTime.Now-time).TotalMilliseconds;
Console.WriteLine(string.Format("Taken {0}", TimeTaken));


I wrote up a loop to check the performance and results were startling. The first two, ( string.empty and == ) took almost double the time string.length took. Of course it is understandle , while former would require comparison to each place in string, the latter only need to know the length.

The point i would like to make here is when you need to check string for empty, it is always better to use string.length if you have performance as your criteria.