[c#] C#: Limit the length of a string?

I was just simply wondering how I could limit the length of a string in C#.

string foo = "1234567890";

Say we have that. How can I limit foo to say, 5 characters?

Use Remove()...

string foo = "1234567890";
int trimLength = 5;

if (foo.Length > trimLength) foo = foo.Remove(trimLength);

// foo is now "12345"

You can try like this:

var x= str== null 
        ? string.Empty 
        : str.Substring(0, Math.Min(5, str.Length));

You could extend the "string" class to let you return a limited string.

using System;

namespace ConsoleApplication1
{
   class Program
   {
      static void Main(string[] args)
      {
         // since specified strings are treated on the fly as string objects...
         string limit5 = "The quick brown fox jumped over the lazy dog.".LimitLength(5);
         string limit10 = "The quick brown fox jumped over the lazy dog.".LimitLength(10);
         // this line should return us the entire contents of the test string
         string limit100 = "The quick brown fox jumped over the lazy dog.".LimitLength(100);

         Console.WriteLine("limit5   - {0}", limit5);
         Console.WriteLine("limit10  - {0}", limit10);
         Console.WriteLine("limit100 - {0}", limit100);

         Console.ReadLine();
      }
   }

   public static class StringExtensions
   {
      /// <summary>
      /// Method that limits the length of text to a defined length.
      /// </summary>
      /// <param name="source">The source text.</param>
      /// <param name="maxLength">The maximum limit of the string to return.</param>
      public static string LimitLength(this string source, int maxLength)
      {
         if (source.Length <= maxLength)
         {
            return source;
         }

         return source.Substring(0, maxLength);
      }
   }
}

Result:

limit5 - The q
limit10 - The quick
limit100 - The quick brown fox jumped over the lazy dog.

foo = foo.Substring(0,5);

If this is in a class property you could do it in the setter:

public class FooClass
{
   private string foo;
   public string Foo
   {
     get { return foo; }
     set
     {
       if(!string.IsNullOrEmpty(value) && value.Length>5)
       {
            foo=value.Substring(0,5);
       }
       else
            foo=value;
     }
   }
}

You can avoid the if statement if you pad it out to the length you want to limit it to.

string name1 = "Christopher";
string name2 = "Jay";
int maxLength = 5;

name1 = name1.PadRight(maxLength).Substring(0, maxLength);
name2 = name2.PadRight(maxLength).Substring(0, maxLength);

name1 will have Chris

name2 will have Jay

No if statement needed to check the length before you use substring

string shortFoo = foo.Length > 5 ? foo.Substring(0, 5) : foo;

Note that you can't just use foo.Substring(0, 5) by itself because it will throw an error when foo is less than 5 characters.

Here is another alternative answer to this issue. This extension method works quite well. This solves the issues of the string being shorter than the maximum length and also the maximum length being negative.

public static string Left( this string str, int length ) {
  if (str == null)
    return str;
  return str.Substring(0, Math.Min(Math.Abs(length), str.Length));
}

Another solution would be to limit the length to be non-negative values, and just zero-out negative values.

public static string Left( this string str, int length ) {
  if (str == null)
    return str;
  return str.Substring(0, Math.Min(Math.Max(0,length), str.Length));
}

The only reason I can see the purpose in this is for DB storage. If so, why not let the DB handle it and then push the exception upstream to be dealt with at the presentation layer?

You can't. Bear in mind that foo is a variable of type string.

You could create your own type, say BoundedString, and have:

BoundedString foo = new BoundedString(5);
foo.Text = "hello"; // Fine
foo.Text = "naughty"; // Throw an exception or perhaps truncate the string

... but you can't stop a string variable from being set to any string reference (or null).

Of course, if you've got a string property, you could do that:

private string foo;
public string Foo
{
    get { return foo; }
    set
    {
        if (value.Length > 5)
        {
            throw new ArgumentException("value");
        }
        foo = value;
    }
}

Does that help you in whatever your bigger context is?