How can I create a more user-friendly string.format syntax

Question

I need to create a very long string in a program, and have been using String.Format. The problem I am facing is keeping track of all the numbers when you have more than 8-10 parameters.

Is it possible to create some form of overload that will accept a syntax similar to this?

String.Format("You are {age} years old and your last name is {name} ",
{age = "18", name = "Foo"});

Answer 1

not quite the same but sort of spoofing it... use an extension method, a dictionary and a little code:

something like this...

  public static class Extensions {

        public static string FormatX(this string format, params KeyValuePair<string, object> []  values) {
            string res = format;
            foreach (KeyValuePair<string, object> kvp in values) {
                res = res.Replace(string.Format("{0}", kvp.Key), kvp.Value.ToString());
            }
            return res;
        }

    }

Answer 2

primitive implementation:

public static class StringUtility
{
  public static string Format(string pattern, IDictionary<string, object> args)
  {
    StringBuilder builder = new StringBuilder(pattern);
    foreach (var arg in args)
    {
      builder.Replace("{" + arg.Key + "}", arg.Value.ToString());
    }
    return builder.ToString();
  }
}

Usage:

StringUtility.Format("You are {age} years old and your last name is {name} ",
  new Dictionary<string, object>() {{"age" = 18, "name" = "Foo"}});

You could also use a anonymous class, but this is much slower because of the reflection you'll need.

For a real implementation you should use regular expression to

• allow escaping the {}
• check if there are placeholders that where not replaced, which is most probably a programming error.

Answer 3

How about the following, which works both for anonymous types (the example below), or regular types (domain entities, etc):

static void Main()
{
    string s = Format("You are {age} years old and your last name is {name} ",
        new {age = 18, name = "Foo"});
}

using:

static readonly Regex rePattern = new Regex(
    @"(\{+)([^\}]+)(\}+)", RegexOptions.Compiled);
static string Format(string pattern, object template)
{
    if (template == null) throw new ArgumentNullException();
    Type type = template.GetType();
    var cache = new Dictionary<string, string>();
    return rePattern.Replace(pattern, match =>
    {
        int lCount = match.Groups[1].Value.Length,
            rCount = match.Groups[3].Value.Length;
        if ((lCount % 2) != (rCount % 2)) throw new InvalidOperationException("Unbalanced braces");
        string lBrace = lCount == 1 ? "" : new string('{', lCount / 2),
            rBrace = rCount == 1 ? "" : new string('}', rCount / 2);

        string key = match.Groups[2].Value, value;
        if(lCount % 2 == 0) {
            value = key;
        } else {
            if (!cache.TryGetValue(key, out value))
            {
                var prop = type.GetProperty(key);
                if (prop == null)
                {
                    throw new ArgumentException("Not found: " + key, "pattern");
                }
                value = Convert.ToString(prop.GetValue(template, null));
                cache.Add(key, value);
            }
        }
        return lBrace + value + rBrace;
    });
}

Answer 4

What about if age/name is an variable in your application. So you would need a sort syntax to make it almost unique like {age_1}?

If you have trouble with 8-10 parameters: why don't use

"You are " + age + " years old and your last name is " + name + "