How to replace occurrences of "-" with an empty string?

This should do the trick:

String st = "123-456-7".Replace("-","");

To be clear, you want to replace each hyphen (-) with blank/nothing. If you replaced it with backspace, it would erase the character before it!

That would lead to: 123-456-7 ==> 12457

Sean Bright has the right answer.

string r = "123-456-7";
r = r.Replace("-", "");

string r = "123-456-7".Replace("-", String.Empty);

For .Net 1.0 String.Empty will not take additional space on the heap but "" requires storage on the heap and its address on the stack resulting in more assembly code. Hence String.Empty is faster than "".

Also String.Empty mean no typo errors.

Check the What is the difference between String.Empty and “” link.