What's the Fastest Way to Count String Occurrences in .NET?

The best way to count the string count

Find all the number of times in the specific character or sub -string in a given string in a .NET. There are many ways to appear. This article focuses on the most effective and convenient method, especially when the slash (/) in the statistical string.

First of all, you can consider using character replacement, for example:

Or, for a sub -string with a length of more than one character, you can use:

<code class="language-csharp">string source = "/once/upon/a/time/";
int count = source.Length - source.Replace("/", "").Length;</code>

But for the .NET 3.5 users, the more concise and efficient solution was to use Linq:

<code class="language-csharp">string haystack = "/once/upon/a/time/";
string needle = "/";
int needleCount = (haystack.Length - haystack.Replace(needle, "").Length) / needle.Length;</code>

or, you can choose:

<code class="language-csharp">int count = source.Count(f => f == '/');</code>

Surprisingly, the initial character removal method is about 30%faster than the Linq or Split method. The benchmark test of the string "/ONCE/Upon/A/Time/" generates the following chronograph results:

<code class="language-csharp">int count = source.Split('/').Length - 1;</code>

Character replacement method: 12 seconds

• Source.Count: 19 seconds
• Source.split: 17 seconds
• Foreach loop (from other answers): 10 seconds
Although these time differences may not be obvious in practical applications, the original character replacement method is still the fastest for this situation.

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