C# string format flag or modifier to lowercase param

Question

Is it possible to specify some kind of flag or modifier on a string format param to make it lower case or upper case?

Example of what I want:

String.Format("Hi {0:touppercase}, you have {1} {2:tolowercase}.", "John", 6, "Apples"); 

Wanted output:

Hi JOHN, you have 6 apples.

PS: Yes I know that I can change the case of the param before using it in the string format, but I don't want this.

Answer 1

There's only padding and allignment formating... So the easy way is like you said, use "John".ToUpper() or "John".ToLower().

Another solution could be create a custom IFormatProvider, to provide the string format you want.

This is how will look the IFormatProvider and the string.Format call.

public class CustomStringFormat : IFormatProvider, ICustomFormatter {     public object GetFormat(Type formatType)     {         if (formatType == typeof(ICustomFormatter))             return this;         else             return null;      }      public string Format(string format, object arg, IFormatProvider formatProvider)     {         string result = arg.ToString();          switch (format.ToUpper())         {             case "U": return result.ToUpper();             case "L": return result.ToLower();             //more custom formats             default: return result;         }     } } 

And the call will look like:

String.Format(new CustomStringFormat(), "Hi {0:U}", "John"); 

Answer 2

In short, no; AFAIK you'd have to fix the source values, or use your own replacement to string.Format. Note that if you are passing in a custom culture (to string.Format) you may want to use culture.TextInfo.ToLower(s), rather than just s.ToLower().