c# - string.format doesn't work on strings -

uhm, have run before. want this.

 phonenumber = string.format("{0:(###) ###-####}", compview.phone_number), 

but! compview.phone_number string :( doesn't work. first thought create extension method thought maybe put out people , see if out in community had better suggestions.

thanks!

if phone number string, can try

phonenumber =  string.format("({0}) {1}-{2}",                   compview.phone_number.substring(0, 3),                   compview.phone_number.substring(3, 3),                   compview.phone_number.substring(6, 4));