c# - Regular Expression for validating numbers with one space and one optional special character

Question

Can someone tell me how to validate sequence of numbers with one space and at the end there will be a optional special character say '#' and again followed by some 5 digits.

Example:

12345 6587#2584

I have tried with

(0(?:d{0,11}|(?=d* d*$)[d ]{0,12}))

but I don't know how to add optional '#' in the end followed by digits.

Answer 1

This should do the trick

/^d+sd+(?:#d+)?$/

See it on rubular

^      beginning of string
d+    one or more numbers
s     any whitespace character
d+    one or more numbers
(?:    begin non-capturing group
  #    literal '#' character
  d+  one or more numbers
)      end non-capturing group
$      end of string

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EDIT

/^0[ds]{,11}(?:#d{,5}?$/

Matches a string starting with 0, followed by a max of 11 numbers or spaces. Followed by an optional # with a max of 5 numbers after it.