iformatprovider

String formatting in C#; Can I use it? Yes. Can I implement custom formatting? No. I need to write something where I can pass a set of custom formatting options to string.Format , which will have some effect on the particular item. at the moment I have something like this: string.Format("{0}", item); but I want to be able to do things with that item: string.Format("{0:lcase}", item); // lowercases the item string.Format("{0:ucase}", item); // uppercases the item string.Format("{0:nospace}", item); // removes spaces I know I can do things like .ToUpper() , .ToLower() etc. but I need to do it

I was playing around with the Datetime.ParseExact method, and it wants an IFormatProvider... It works inputting null, but what exactly does it do? In adition to Ian Boyd's answer: Also CultureInfo implements this interface and can be used in your case. So you could parse a French date string for example; you could use var ci = new CultureInfo("fr-FR"); DateTime dt = DateTime.ParseExact(yourDateInputString, yourFormatString, ci); The IFormatProvider interface is normally implemented for you by a CultureInfo class, e.g.: CultureInfo.CurrentCulture CultureInfo.CurrentUICulture CultureInfo

var numberFormat = new NumberFormatInfo(); numberFormat.NumberDecimalSeparator = "."; numberFormat.NumberDecimalDigits = 2; decimal a = 10.00M; decimal b = 10M; Console.WriteLine(a.ToString(numberFormat)); Console.WriteLine(b.ToString(numberFormat)); Console.WriteLine(a == b ? "True": "False"); In console: 10.00 10 True Why is it different? More important, how do I call ToString() to ensure same output no matter how a variable is initialized? The NumberDecimalDigits property is used with the "F" and "N" standard format strings, not the ToString method called without a format string. You can