This is just another quick example of Regex pattern.

Next pattern matches “at least one symbol which is letter or digit at the begging and then exactly one delimiter ‘|’ and then at least one symbol which is letter or digit in the end“:

var valuePattern = new Regex(@”^w+|w+$”);
bool isValid = valuePattern.IsMatch(someStringValue);

Valid is:

ab123|cde45

Not valid are:

|ad
df|
adf||adf

and so on…

Links I’ve used:

Verify your Regex:  
http://www.pagecolumn.com/tool/regtest.htm
Cheat Sheet:
http://www.addedbytes.com/download/regular-expressions-cheat-sheet-v2/pdf/