c# Regex match and replace using function

Question

/// <summary>
/// Given HTML overlay for an image in the store, render it.
/// [p:n] renders as price for item ID n
/// </summary>
/// <returns>Rendered result</returns>
public static string RenderHTMLOverlay(string overlayHTML, int currencyID)
{
    const string pattern = "\\[p\\:(\\b\\d+\\b)\\]";
    overlayHTML = Regex.Replace(overlayHTML, pattern, FormatCurrency(GetItemPriceOnDate(DateTime.Now, currencyID, int.Parse("$1"))));

    return overlayHTML;
}

This doesn't work because $1 can't be passed as a parameter correctly to int.Parse.

Exception Details: System.FormatException: Input string was not in a correct format.

Does anyone know how I can work around this limitation?

Not related to the question, but I'd suggest using @"\[p\:(\b\d+\b)\]" instead if your expression for pattern. Means the same thing and is more readable. — ikh
– ikh, Commented Jul 30, 2012 at 16:55
Even better: @"\[p:(\d+)\]". The colon doesn't need escaping and the word boundaries are redundant. — Alan Moore
– Alan Moore, Commented Jul 30, 2012 at 20:29

Arithmomaniac · Accepted Answer · 2018-09-13 14:46:13Z

3

You can only use the $1 notation if the replacement argument is a string, so you ended up passing $1 as a literal string to the int.Parse method.

Instead, use the (String, String, MatchEvaluator) overload with an anonymous method:

Regex.Replace(overlayHTML, pattern, 
match => FormatCurrency(GetItemPriceOnDate(DateTime.Now, currencyID, int.Parse(match.Groups[1].Value)))
)

edited Sep 13, 2018 at 14:46

answered Jul 30, 2012 at 16:55

Arithmomaniac

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Comments

GrayFox374 · Accepted Answer · 2012-07-30 17:02:39Z

-1

I'm not totally sure I understand you, so bear with me if I am off.

 Console.WriteLine(int.Parse("$1"));  //throws exception Input string was not in a correct format.

 Console.WriteLine(int.Parse("$1".Replace("$", "")));  //Result: 1

If Store.CommonFunctions.GetItemPriceOnDate returns a string, you should be good to go.

answered Jul 30, 2012 at 17:02

GrayFox374

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