Regex pattern for checking if a string starts with a certain substring?

Question

What's the regular expression to check if a string starts with "mailto" or "ftp" or "joe" or...

Now I am using C# and code like this in a big if with many ors:

String.StartsWith("mailto:") String.StartsWith("ftp") 

It looks like a regex would be better for this. Or is there a C# way I am missing here?

Answer 1

You could use:

^(mailto|ftp|joe) 

But to be honest, StartsWith is perfectly fine to here. You could rewrite it as follows:

string[] prefixes = { "http", "mailto", "joe" }; string s = "joe:bloggs"; bool result = prefixes.Any(prefix => s.StartsWith(prefix)); 

You could also look at the System.Uri class if you are parsing URIs.

Answer 2

The following will match on any string that starts with mailto, ftp or http:

 RegEx reg = new RegEx("^(mailto|ftp|http)"); 

To break it down:

• ^ matches start of line
• (mailto|ftp|http) matches any of the items separated by a |

I would find StartsWith to be more readable in this case.