Question

Using C#, what’s the most efficient way to accomplish this?

string one = "[phone]";
string two = "2221239876";

// combine these into result

result = "[phone]"

String one will always have 9’s.

I’m thinking some kind of foreach on string one and when it sees a 9, replace it with the next character in string two. Not quite sure where to go from there though…

Answer 1

If you want to apply a certain format to a number, you can try this:

long number = 2221239876;
string result = number.ToString("(###) ### ####");    // Result: [phone]

For more information, see Custom Numeric Format Strings in the .NET Framework documentation.