StartsWith

This C# method tests the first part of strings. We use it to test the first characters in a string against another string. It is possible to test many strings with the foreach-loop.

With EndsWith, we test the last characters. These two methods provide an easy way to test and match common strings such as URLs. They are used throughout C# programs.

Example

We can use StartsWith and EndsWith to check the beginning and end of strings. These methods can be used for efficient testing of strings that have known starts or ends.

using System;

// The input string.
string input = "abcdef";
if (input.StartsWith("abc"))
{
    Console.WriteLine("STARTSWITH: ABC");
}
if (input.EndsWith("def"))
{
    Console.WriteLine("ENDSWITH: DEF");
}
STARTSWITH: ABC
ENDSWITH: DEF

Foreach, StartsWith

Next, we see that foreach can be used with StartsWith. Here we test elements in a string array against the input string, returning true if there is a match.

using System;

// The input string.
string input = "http://site.com/test.html";

// The possible matches.
string[] urls = new string[]
{
    "http://www.site.com",
    "http://site.com"
};

// Loop through each possible match.
foreach (string value in urls)
{
    if (input.StartsWith(value))
    {
        // Will match second possibility.
        Console.WriteLine(value);
        return;
    }
}
http://site.com

EndsWith

This tests the last parts of strings. It finds strings that have a certain ending sequence of characters. EndsWith is a simple way to test for ending substrings.

using System;

// The input string.
string input = "http://site.com";

// Test these endings.
string[] array = new string[]
{
    ".net",
    ".com",
    ".org"
};

// Loop through and test each string.
foreach (string value in array)
{
    if (input.EndsWith(value))
    {
        Console.WriteLine(value);
        return;
    }
}
.com

Overloads

StartsWith accepts a second parameter—a StringComparison enumerated constant. You can use String Comparison to specify case-insensitive matching—try OrdinalIgnoreCase.

Char test, performance

Consider the StartsWith method: we can duplicate its functionality with individual char tests. In benchmarks, testing chars usually is faster.

With StartsWith we can test the first characters of strings. It returns a bool telling us whether or not the starts match. EndsWith, meanwhile, tests the end of strings.