Remove

This C# string method eliminates a range of characters. It is useful for shortening strings. It creates a new string when it is called.

This method can often be used alongside other methods like IndexOf. We review examples of using Remove with 1 or 2 arguments.

In this example, we call Remove() in 2 different ways. The first argument is an int that indicates where the method should start removing characters—a start index.

using System;

// Version 1: use 1 argument with Remove.
// ... Remove all characters after an index.
string test1 = "0123456";
string result1 = test1.Remove(3);
Console.WriteLine(result1);

// Version 2: use 2 arguments with Remove.
// ... Remove range of characters in string.
string test2 = "012 345 678";
int index1 = test2.IndexOf(' ');
int index2 = test2.IndexOf(' ', index1 + 1);
string result2 = test2.Remove(index1, index2 - index1);
Console.WriteLine(result2);
012
012 678

Remove char

One use for Remove is to erase or delete the final character in a string, or erase the first character. Remove() acts on strings, but it can remove a single character too.

using System;

class Program
{
    static void Main()
    {
        // Part 1: remove the last character in a string.
        string test1 = "0123456";
        test1 = test1.Remove(test1.Length - 1);
        Console.WriteLine(test1);

        // Part 2: remove the first character in a string.
        string test2 = "0123456";
        test2 = test2.Remove(0, 1);
        Console.WriteLine(test2);
    }
}
012345
123456

Trim, remove

Other string methods (like TrimStart, TrimEnd, or Trim) can also remove certain characters in a string. The effect is sometimes the same as calling Remove ourselves.

using System;

class Program
{
    static void Main()
    {
        string test = "aaabird";

        // Remove chars at the start with TrimStart and Remove.
        // ... These methods do different things, but sometimes can be exchanged.
        string trimmedString = test.TrimStart(new char[] { 'a' });
        string removedString = test.Remove(0, 3);

        Console.WriteLine("TRIMMED STRING: " + trimmedString);
        Console.WriteLine("REMOVED STRING: " + removedString);
    }
}
TRIMMED STRING: bird
REMOVED STRING: bird

Performance

Here we benchmarked the Remove method against an equivalent Substring call. Remove() internally calls substring, so this tests the overhead of the Remove-specific logic.

using System;
using System.Diagnostics;

const int _max = 100000000;
string source = "012 345 678";
int length = source.Length - 3;

var s1 = Stopwatch.StartNew();
// Version 1: use Substring.
for (int i = 0; i < _max; i++)
{
    string result = source.Substring(0, 3);
    if (result == null)
    {
        return;
    }
}
s1.Stop();
var s2 = Stopwatch.StartNew();
// Version 2: use Remove.
for (int i = 0; i < _max; i++)
{
    string result = source.Remove(3, length);
    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"));
13.18 ns    Substring
14.58 ns    Remove

Discussion

We can call Replace with an empty replacement string, which will remove substrings. However this is less exact than using Remove.

Special methods

We can develop a string truncation method that has some internal logic to help us remove string parts easier. We can remove a single char from a string.

With the Remove() method, we delete a range of characters. We can specify 1 or 2 arguments, and a modified string is returned.