Extracting Just The SessionID

I am trying to extract just the session id from some iislogs, and was curious the best way to go about doing this. The session ids will all be like "ASP.NET_SessionId=1wtdqn241f0ews55n5hsipib" with 42 chars in length, however the sessionid can be anywhere in the column, sometimes by itself, sometimes at the beginning and sometimes near the end. I guess the best way to do this is search for %ASP.NET_% but im not sure how to pull just the sessionid out.

does anyone know how I should approach this or where this topic has been brought up in the forums so I could get an idea. I tried searching by instr and sessionid and few others.

Thanks

SAMPLES WHAT THE DATA MIGHT LOOK LIKE
ASP.NET_SessionId=3mhnrf45wwiypi45polih5ey

ASP.NET_SessionId=ejsfrueqay4tuo45iuszsy45;+.RELYFORMSAUTH=C81CBCADBC5DEB801A3D4EBBC187A063CFCB70D678C1419BBFBE49B06CEE0039EBC85A9592882C15E47B69BD2FBE82A570B3F93011EA95B905301FC547DE67E68D3B5EB0E53CA824EC271A0B4EF8092E

.OASIS7FORMSAUTH=34720D24F742723CD786480BC252E8ABE392B2EC146FC1474501C3BC2A8126FF0539AD35BB14D0B259F366289611B1C696724932DE0C792AAD60B3867430EB8D3540F7B36991A851924F465A5E00CC2B;+ASP.NET_SessionId=3mhnrf45wwiypi45polih5ey