c# regexp pattern to <id> .... </id>

I wrote the following pattern:

@"<([0-9]+)>(.*?) < /$1&g开发者_Go百科t;"

but it doesn't work. how could i refer to the first group?

source text:

"Method()<0>int x = 0; while(x < 10)<1>echo(x)< /1>< /0>"

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That would be \1, and watch for spaces.
See also: .Net Regex Backreferencing