How can I limit a string to no more than a certain length?

Question

I tried the following:

var Title = LongTitle.Substring(0,20)

This works but not if LongTitle has a length of less than 20. How can I limit strings to a maximum of 20 characters but not get an error if they are just for example 5 characters long?

Check the length of the string, and if it's greater than 20 characters truncate, otherwise leave it as is. — Tim, Jun 22 '13 at 10:20

score 43 · Answer 1 · edited May 03 '18 at 20:24

43

Make sure that length won't exceed LongTitle (null checking skipped):

int maxLength = Math.Min(LongTitle.Length, 20);
string title = LongTitle.Substring(0, maxLength);

This can be turned into extension method:

public static class StringExtensions
{

    /// <summary>
    /// Truncates string so that it is no longer than the specified number of characters.
    /// </summary>
    /// <param name="str">String to truncate.</param>
    /// <param name="length">Maximum string length.</param>
    /// <returns>Original string or a truncated one if the original was too long.</returns>
    public static string Truncate(this string str, int length)
    {
        if(length < 0)
        {
            throw new ArgumentOutOfRangeException(nameof(length), "Length must be >= 0");
        }

        if (str == null)
        {
            return null;
        }

        int maxLength = Math.Min(str.Length, length);
        return str.Substring(0, maxLength);
    }
}

Which can be used as:

string title = LongTitle.Truncate(20);

edited May 03 '18 at 20:24

Decius

155
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11

answered Jun 22 '13 at 10:18

Zbigniew

27,184
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Maybe also checking for `null` in the extension method? – Uwe Keim Jun 22 '13 at 10:26
1

I too have used an extension method for this, but out of respect for others who maintain my code (and for the sake of brevity), might I suggest a more apt method signature: Truncate(int maxLength) – Chris Jun 22 '13 at 10:32
@Chris Yes, this is indeed much better name for this method :) Thank you – Zbigniew Jun 22 '13 at 10:34
1

length also could be optional parameter. – adt Jun 22 '13 at 10:39
@adt You're free to do whatever you like with this method. `length` could be optional, but what value would it take? `0`? Does it even makes sanse to truncate string to empty string? – Zbigniew Jun 22 '13 at 10:42

AgentFire · Answer 2 · 2023-08-10T18:12:42.800

18

Shortest, the:

var title = longTitle.Substring(0, Math.Min(20, longTitle.Length))

Update

Ok since some new C# version this suggested variant became the shortest:

var title = longTitle[..Math.Min(20, longTitle.Length)]

edited Aug 10 '23 at 18:12

answered Jun 22 '13 at 10:30

AgentFire

8,944
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1

Shorter: var Title = longTitle[..Math.Min(20, longTitle.Length)] – Danie Mar 21 '23 at 15:11

score 9 · Answer 3 · answered Jun 22 '13 at 10:20

9

string title = new string(LongTitle.Take(20).ToArray());

answered Jun 22 '13 at 10:20

cuongle

74,024
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5

Note this is quite inefficient since it create an intermediate char array which is then immediately copied and discarded. – Lee Jun 22 '13 at 10:26
2

@Lee: You are right, but with small string, it's trivial – cuongle Jun 22 '13 at 10:32

score 5 · Answer 4 · answered Jun 22 '13 at 10:22

5

If the string Length is bigger than 20, use 20, else use the Length.

string  title = LongTitle.Substring(0,
    (LongTitle.Length > 20 ? 20 : LongTitle.Length));

answered Jun 22 '13 at 10:22

Peter Rasmussen

16,474
7
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2

Learn to use Math.Min for this purpose. – Chris Jun 22 '13 at 10:33

score 3 · Answer 5 · answered Jun 22 '13 at 10:35

You can use the StringLength attribute. That way no string can be stored that is longer (or shorter) than a specified length.

See: http://msdn.microsoft.com/en-us/library/system.componentmodel.dataannotations.stringlengthattribute%28v=vs.100%29.aspx

[StringLength(20, ErrorMessage = "Your Message")]
public string LongTitle;

How can I limit a string to no more than a certain length?

5 Answers5

Update

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