TrimEnd, TrimStart

In C# TrimEnd removes ending characters from a string. Suppose we have a string with trailing punctuation. We can use TrimEnd to remove these characters.

Meanwhile, TrimStart removes from the start of a string. These methods are useful, and their effects are simple—they return copied strings.

TrimEnd

This program loops through an array and trims it sending characters with TrimEnd. We use a string array. The results are printed to the screen.

using System;

// Our example string array.
string[] items = new string[]
{
    "test?",
    "ok..."
};

// Loop and call TrimEnd.
foreach (string item in items)
{
    string trimmed = item.TrimEnd('?', '.', ',');
    Console.WriteLine(item);
    Console.WriteLine(trimmed);
}
test?
test
ok...
ok

TrimStart

TrimStart removes leading characters. Sometimes strings have starting characters that are not needed. TrimStart removes as many characters of the specific values as required.

using System;

// Trim this string.
string text = "\t, again and again.";
// Trim these characters.
char[] array = new char[] { '\t', ',', ' ' };

text = text.TrimStart(array);
Console.WriteLine(text);
again and again.

Benchmark, trimming

Custom implementations of TrimEnd are faster than the version included in .NET. You can use a for-loop from the last index of the string.

using System;
using System.Diagnostics;

class Program
{
    static string TrimTrailingChars(string value)
    {
        int removeLength = 0;
        for (int i = value.Length - 1; i >= 0; i--)
        {
            char let = value[i];
            if (let == '?' || let == '!' || let == '.')
            {
                removeLength++;
            }
            else
            {
                break;
            }
        }
        if (removeLength > 0)
        {
            return value.Substring(0, value.Length - removeLength);
        }
        return value;
    }

    const int _max = 10000000;
    static void Main()
    {
        var paramArray = new char[] { '?', '!', '.' };
        var s1 = Stopwatch.StartNew();
        // Version 1: use optimized method.
        for (int i = 0; i < _max; i++)
        {
            var result = TrimTrailingChars("hello!?");
            if (result == null)
            {
                return;
            }
        }
        s1.Stop();
        var s2 = Stopwatch.StartNew();
        // Version 2: use TrimEnd.
        for (int i = 0; i < _max; i++)
        {
            var result = "hello!?".TrimEnd(paramArray);
            if (result == null)
            {
                return;
            }
        }
        s2.Stop();
        Console.WriteLine(((double)(s1.Elapsed.TotalMilliseconds * 1000000) / _max).ToString("0.00 ns"));
        Console.WriteLine(((double)(s2.Elapsed.TotalMilliseconds * 1000000) / _max).ToString("0.00 ns"));
    }
}
13.54 ns    Optimized method
15.85 ns    TrimEnd

TrimEnd and TrimStart can be used with array parameters. They remove chars from the end and start of strings. They remove all characters specified until they can't remove one.