Question

I’m using asp.net/C# and I’m looking to create unique(?) uris for a small CMS system I am creating.

I am generating the uri segment from my articles title, so for example if the title is “My amazing article” the uri would be http://www.website.com/news/my-amazing-article

There are two parts to this. Firstly, which characters do you think I need to strip out? I am replacing spaces with “-” and I think I should strip out the “/” character too. Can you think of any more that might cause problems? “?” perhaps? Should I remove all non-alpha characters?

Second question, above I mentioned the uris MAY need to be unique. I was going to check the uri list before adding to ensure uniqueness, however I see stack overflow uses a number plus a uri. This I assume allows titles to be duplicated? Do you think this would be a better way?

Answer 1

Transform all diacritics into their base character and then strip anything that is not a letter or a digit using Char.IsLetterOrDigit.

Then replace all spaces by a single dash.

This is what we use in our software.

/// <summary>
/// Convert a name into a string that can be appended to a Uri.
/// </summary>
private static string EscapeName(string name)
{
    if (!string.IsNullOrEmpty(name))
    {
        name = NormalizeString(name);

        // Replaces all non-alphanumeric character by a space
        StringBuilder builder = new StringBuilder();
        for (int i = 0; i < name.Length; i++)
        {
            builder.Append(char.IsLetterOrDigit(name[i]) ? name[i] : ' ');
        }

        name = builder.ToString();

        // Replace multiple spaces into a single dash
        name = Regex.Replace(name, @"[ ]{1,}", @"-", RegexOptions.None);
    }

    return name;
}

/// <summary>
/// Strips the value from any non english character by replacing thoses with their english equivalent.
/// </summary>
/// <param name="value">The string to normalize.</param>
/// <returns>A string where all characters are part of the basic english ANSI encoding.</returns>
/// <seealso cref="http://stackoverflow.com/questions/249087/how-do-i-remove-diacritics-accents-from-a-string-in-net"/>
private static string NormalizeString(string value)
{
    string normalizedFormD = value.Normalize(NormalizationForm.FormD);
    StringBuilder builder = new StringBuilder();

    for (int i = 0; i < normalizedFormD.Length; i++)
    {
        UnicodeCategory uc = CharUnicodeInfo.GetUnicodeCategory(normalizedFormD[i]);
        if (uc != UnicodeCategory.NonSpacingMark)
        {
            builder.Append(normalizedFormD[i]);
        }
    }

    return builder.ToString().Normalize(NormalizationForm.FormC);
}

Concerning using those generated name as unique Id, I would vouch against. Use the generated name as a SEO helper, but not as a key resolver. If you look at how stackoverflow references their pages:

http://stackoverflow.com/questions/249087/how-do-i-remove-diacritics-accents-from-a-string-in-net
                                   ^--ID  ^--Unneeded name but helpful for bookmarks and SEO

You can find the ID there. These two URL point to the same page:

http://stackoverflow.com/questions/249087/how-do-i-remove-diacritics-accents-from-a-string-in-net

http://stackoverflow.com/questions/249087/