How to provide custom string placeholder for string format

Question

I have a string

string str =\"Enter {0} patient name\";

I am using string.format to format it.

String.Format(str, \"Hello\         


        

Answer 1

Regex with a MatchEvaluator seems a good option:

static readonly Regex re = new Regex(@"\{([^\}]+)\}", RegexOptions.Compiled);
static void Main()
{
    string input = "this {foo} is now {bar}.";
    StringDictionary fields = new StringDictionary();
    fields.Add("foo", "code");
    fields.Add("bar", "working");

    string output = re.Replace(input, delegate (Match match) {
        return fields[match.Groups[1].Value];
    });
    Console.WriteLine(output); // "this code is now working."
}