What is the C# equivalent of java.util.regex?

I am converting Java code to C# and need to replace the use of Java's regex. A typical use is

import java.util.regex.Matcher;
import java开发者_Python百科.util.regex.Pattern;
//...

String myString = "B12";
Pattern pattern = Pattern.compile("[A-Za-z](\\d+)");
Matcher matcher = Pattern.matcher(myString);
String serial = (matcher.matches()) ? matcher.group(1) : null;

which should extract a capture group from a matched target string. I'd be grateful for simple examples.

EDIT: I have now added the C# equivalent of the code as an answer.

EDIT: Here is a tutorial on the use of the actual expressions.

EDIT: Here is a useful comparison of C# and Java (and Perl.)

System.Text.RegularExpressions.Regex class is the .NET Framework equivalent. The MSDN page I linked to contains a simple example.

I created the C# equivalent of the Java code in the question as:

string myString = "B12";
Regex rx = new Regex(@"[A-Za-z](\\d+)");
MatchCollection matches = rx.Matches(myString);
if (matches.Count > 0)
{
    Match match = matches[0]; // only one match in this case
    GroupCollection groupCollection = match.Groups;
    Console.WriteLine("serial " + groupCollection[1].ToString());
}

EDIT (See @Mehrdad's helpful comments)

The original code was:

// ...

MatchCollection matches = rx.Matches(myString);
foreach (Match match in matches)
{
    GroupCollection groupCollection = match.Groups;
    Console.WriteLine("serial " + groupCollection[1].ToString());
}