Helper to generate "friendly URL" in Razor (C#/MVC 4)

Question

The goal

Create something that converts string to friendly string in Razor (I'm using C#/MVC4)

The problem

I have the following code:

<li>
   <img 
    src="~/Images/Products/@Model["CategoryName"]/@Model["ProductThumbnailUrl"]"
   />
</li>

The name of my categories are like: CDs, DVDs and Blurayand I want to concatenate as "friendly-string" like cds-dvds-and-blurays using something like this:

<li>
   <img 
    src="~/Images/Products
          /@HtmlHelper.ConvertToFriendlyString(@Model["CategoryName"])
          /@Model["ProductThumbnailUrl"]"
   />
</li>

Can you all understand?

So, someone have any idea?

Thanks in advance.

Answer 1

I've done this before. While I dig up the code, here are things to keep in consideration:

1. Make sure you store your generated URLs so you can do collision detection; converting strings to friendly URLs is almost certainly going to be lossy, so you need logic to resolve conflicted names.
2. You ought to try to convert diacritical marks into more easily-typable characters.
3. Consider making url-to-resource mappings a 1:many relationship; if the name of your resource changes, you may want to generate a new URL and have the old URL redirect to the new.

UPDATE: Here is my code for this. The Stack Overflow approach is OK, but I like mine better; instead of using a set of character substitutions, it uses the great .NET Unicode library to create friendlier characters:

public static string ConvertToFriendlyUrl(string text)
{
    var decomposed = text.Normalize(NormalizationForm.FormKD);
    var builder = new StringBuilder();
    foreach (var ch in decomposed)
    {
        var charInfo = CharUnicodeInfo.GetUnicodeCategory(ch);
        switch (charInfo)
        {
            // Keep these as they are
            case UnicodeCategory.DecimalDigitNumber:
            case UnicodeCategory.LetterNumber:
            case UnicodeCategory.LowercaseLetter:
            case UnicodeCategory.CurrencySymbol:
            case UnicodeCategory.OtherLetter:
            case UnicodeCategory.OtherNumber:
                builder.Append(ch);
                break;

            // Convert these to dashes
            case UnicodeCategory.DashPunctuation:
            case UnicodeCategory.MathSymbol:
            case UnicodeCategory.ModifierSymbol:
            case UnicodeCategory.OtherPunctuation:
            case UnicodeCategory.OtherSymbol:
            case UnicodeCategory.SpaceSeparator:
                builder.Append('-');
                break;

            // Convert to lower-case
            case UnicodeCategory.TitlecaseLetter:
            case UnicodeCategory.UppercaseLetter:
                builder.Append(char.ToLowerInvariant(ch));
                break;

            // Ignore certain types of characters
            case UnicodeCategory.OpenPunctuation:
            case UnicodeCategory.ClosePunctuation:
            case UnicodeCategory.ConnectorPunctuation:
            case UnicodeCategory.Control:
            case UnicodeCategory.EnclosingMark:
            case UnicodeCategory.FinalQuotePunctuation:
            case UnicodeCategory.Format:
            case UnicodeCategory.InitialQuotePunctuation:
            case UnicodeCategory.LineSeparator:
            case UnicodeCategory.ModifierLetter:
            case UnicodeCategory.NonSpacingMark:
            case UnicodeCategory.OtherNotAssigned:
            case UnicodeCategory.ParagraphSeparator:
            case UnicodeCategory.PrivateUse:
            case UnicodeCategory.SpacingCombiningMark:
            case UnicodeCategory.Surrogate:
                break;
        }
    }

    var built = builder.ToString();
    while (built.Contains("--")) 
        built = built.Replace("--", "-");
    while (built.EndsWith("-"))
    {
        built = built.Substring(0, built.Length - 1);
    }
    while (built.StartsWith("-"))
    {
        built = built.Substring(1, built.Length - 1);
    }
    return built;
}

public static string GetIncrementedUrl(string url)
{
    var parts = url.Split('-');
    var lastPortion = parts.LastOrDefault();
    int numToInc;
    bool incExisting;
    if (lastPortion == null)
    {
        numToInc = 1;
        incExisting = false;
    }
    else
    {
        if (int.TryParse(lastPortion, out numToInc))
        {
            incExisting = true;
        }
        else
        {
            incExisting = false;
            numToInc = 1;
        }
    }

    var fragToKeep = incExisting 
        ? string.Join("-", parts.Take(parts.Length - 1).ToArray()) 
        : url;
    return fragToKeep + "-" + (numToInc + 1).ToString();
}

public static string SeekUrl(
    string name, Func<string, bool> uniquenessCheck)
{
    var urlName = UrlUtils.ConvertToFriendlyUrl(name);
    while (!uniquenessCheck(urlName))
    {
        urlName = UrlUtils.GetIncrementedUrl(urlName);
    }

    return urlName;
}