When using String.Format is there a simple way to add parenthesis around a string value if it is not null or empty.

Question

I am attempting to isolate (for localization purposes) the formatting of some messages. In one of the cases, I have several parameters, some of which may be an empty string. An example is probably called for here....

If the parameters are Parameter one and Parameter two then I want the result to be Some message Parameter one (Parameter two).

If the parameters are Parameter one and string.Empty then I want the result to be Some message Parameter one

If Parameter two was a numeric value, then I could use something like:

String.Format("Test {0}{1:' ('#')'}", "Parameter one", 12);

This operates as I'd expect - specifically if the second parameter is null the output is just Test Parameter one.

Unfortunately I haven't (yet) found a similar option which works with string parameters. Is there one?

Clarification: I am fully aware of numerous ways to get the result I need in code. I specifically want to know if there is a similar built-in mechanism for strings to the numeric one shown above.

Answer 1

You could always attempt writing your own custom string formatter by implementing IFormatProvider and ICustomFormatter

Then invoke it as

var stringValue = string.Format(new NewCustomStringFormatInfo(),
     "Test {0}{1:' ('#')'}", "Parameter one", 12)

Answer 2

var s = System.String.IsNullOrEmpty(param2) ? string.Format(...) : string.Format(...)

Answer 3

Depends on your situation, but you could do

string.Format(yourFormatString, paramOne, paramTwo).Replace("()", "");

No guarantees, as it is not fool-proof and makes the large assumption that your resulting string would only have "()" if paramTwo was empty.

Answer 4

Unless you define a function that encloses a value in brackets, I can't see how you do it inline?

A simple example:

string.Format("Some message {0} {1}", "Parameter one", EncloseInParenthsisIfNotEmpty(""))

public string EncloseInParenthsisIfNotEmpty(string input)
{
    if (string.IsNullOrEmpty(input)) return "";
    return string.Format("({0})", input);
}

Answer 5

You could create an extension method to help handle this and make it a little more concise.

public static string SomeWellNamedExtension(this string s)
{
    if(string.IsNullOrEmpty(s))
        return "";

    return string.Format("({0})", s);
}

This method will handle the null/empty check and the parens. It's a pretty specialized method, so it's not likely to be useful almost anywhere else. But then your code would be like:

string.Format("Test {0}{1}, paramOne, paramTwo.SomeWellNamedExtension());

However, ymmv. This will affect your format string in that the parens are no longer its responsibility. I can't think of many super elegant ways of handling the use case you are talking detailing.

Answer 6

You could write your own wrapper of String.Format (untested):

string MyFormat(string format, params object[] args)
{
  object[] newArgs = new object[args.Length];
  for(int i=0; i<args.Length; i++)
  {
    if(args[i] is string)
    {
      newArgs[i] = String.IsNullOrEmpty(args[i] as string) ? "" : string.Format("({0})", args[i]);
    }
    //numeric cases etc
    else
    { 
      newArgs[i]=args[i];
    }
  }
  return string.Format(format, newArgs);
}