c# - String.Format() not invoking custom formatter -

c# - String.Format() not invoking custom formatter -

i have custom formatter specified, this:

public class notationnumericformatter : iformatprovider, icustomformatter { public object getformat(type formattype_) { homecoming (formattype_ == typeof(icustomformatter) ? : null; } public string format(string format_, object arg_, iformatprovider formatprovider_) { if (!equals(formatprovider_) || arg_ == null) // <-- set breakpoint here... { return; } // bunch of stuff happens here. } }

what's stumping me @ moment is, next code:

// _myformatter notationnumericformatter gets instanced // in ctor of class in question. var result = string.format(_myformatter, (parameter_ ?? "").tostring(), value_);

which never, ever, hitting first line in formatter's format() method. missing here? there subtlety string.format i'm missing?

if parameter not have {0} formatter won't break point

this breakpoint

var result = string.format(_myformatter, "{0}", value_);

this won't

var result = string.format(_myformatter, "", value_);

c# string-formatting