CODEWITHSUNDEEP
c#.netsubstring
Superbest
Superbest

Reputation: 26612

First n characters of a string, even if it is shorter than n?

Say I have string s. I want to return s if s is shorter than n characters, and otherwise return s.Substring(0, n).

What's the easiest way of doing this?

Upvotes: 5

Views: 4915

Answers (4)

Airn5475
Airn5475

Reputation: 2492

If the string is shorter or equal to the desired length, just return the string. Do not call Substring just to return the entire string.

var result = s.Length <= n ? s : s.Substring(0, n);

Upvotes: 0

Dmitri Trofimov
Dmitri Trofimov

Reputation: 574

Tiny bit slower than Superbest's solution:

string result = s.Substring(0, Math.Min(s.Length, n));

Upvotes: 4

Matthew Watson
Matthew Watson

Reputation: 109742

Best approach is to write a couple of extension methods.

Then you can just use it like string result = sourceString.Left(10);

public static class StringExt
{
    /// <summary>
    /// Returns the first <paramref name="count"/> characters of a string, or the entire string if it
    /// is less than <paramref name="count"/> characters long.
    /// </summary>
    /// <param name="self">The string. Cannot be null.</param>
    /// <param name="count">The number of characters to return.</param>
    /// <returns>The first <paramref name="count"/> characters of the string.</returns>

    public static string Left(this string self, int count)
    {
        Contract.Requires(self != null);
        Contract.Requires(count >= 0);

        Contract.Ensures(Contract.Result<string>() != null);
        // ReSharper disable PossibleNullReferenceException
        Contract.Ensures(Contract.Result<string>().Length <= count);
        // ReSharper restore PossibleNullReferenceException

        if (self.Length <= count)
            return self;
        else
            return self.Substring(0, count);
    }

    /// <summary>
    /// Returns the last <paramref name="count"/> characters of a string, or the entire string if it
    /// is less than <paramref name="count"/> characters long.
    /// </summary>
    /// <param name="self">The string. Cannot be null.</param>
    /// <param name="count">The number of characters to return.</param>
    /// <returns>The last <paramref name="count"/> characters of the string.</returns>

    public static string Right(this string self, int count)
    {
        Contract.Requires(self != null);
        Contract.Requires(count >= 0);

        Contract.Ensures(Contract.Result<string>() != null);
        // ReSharper disable PossibleNullReferenceException
        Contract.Ensures(Contract.Result<string>().Length <= count);
        // ReSharper restore PossibleNullReferenceException

        if (self.Length <= count)
            return self;
        else
            return self.Substring(self.Length - count, count);
    }
}

Upvotes: 0

Superbest
Superbest

Reputation: 26612

The quickest way I know is:

var result = s.Length < n ? s : s.Substring(0, n);

Upvotes: 11

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