How to get the substring in C#?

Question

Hi, I can get the first three characters with the function below.

However, how can I get the output of the last five characters (Three) with Substring() function. Or other string function will be used?

Thank you.

static void Main()
        {
            string input = "OneTwoThree";

            // Get first three characters
            string sub = input.Substring(0, 3);
            Console.WriteLine("Substring: {0}", sub); // Output One. 
        }

Answer 1

string sub = input.Substring(input.Length - 5);

Answer 2

One way is to use the Length property of the string as part of the input to Substring:

string sub = input.Substring(input.Length - 5); // Retrieves the last 5 characters of input

Answer 3

If your input string could be less than five characters long then you should be aware that string.Substring will throw an ArgumentOutOfRangeException if the startIndex argument is negative.

To solve this potential problem you can use the following code:

string sub = input.Substring(Math.Max(0, input.Length - 5));

Or more explicitly:

public static string Right(string input, int length)
{
    if (length >= input.Length)
    {
        return input;
    }
    else
    {
        return input.Substring(input.Length - length);
    }
}

Answer 4

If you can use extension methods, this will do it in a safe way regardless of string length:

public static string Right(this string text, int maxLength)
{
    if (string.IsNullOrEmpty(text) || maxLength <= 0)
    {
        return string.Empty;
    }

    if (maxLength < text.Length)
    {
        return text.Substring(text.Length - maxLength);
    }

    return text;
}

And to use it:

string sub = input.Right(5);