Is it possible to decode EventValidation and ViewState in ASP.NET?

Question

How to decode the ASP.NET EventValidation and ViewState?

For ViewState, see "How to decode viewstate": [http://stackoverflow.com/questions/22814/how-to-decode-viewstate/](http://stackoverflow.com/questions/22814/how-to-decode-viewstate/). — XP1, Mar 10 '13 at 18:21

score 3 · Accepted Answer · edited May 23 '17 at 12:10

I answered a similar question recently, Getting values from viewstate using JQuery?.

Basically, by default ViewState is just Base64-encoded, so you can decode it as long as the administrator hasn't configured the site to encrypt it. Quoting from my previous answer:

If you are writing the control for your own consumption and you only need to read from ViewState, you could do so, but I wouldn't recommend it unless you find a well-debugged library to parse it for you. The format is a bit hairy (see ViewState: All You Wanted to Know for more details).

That link provides an extremely thorough and clear introduction to ViewState.

As for Event Validation, I'm unsure whether it's Base64-encoded or if it just looks like Base64 (I can't find a conclusive, authoritative reference). This Rexiology article might help though.

score 2 · Answer 2 · answered Jul 07 '09 at 14:43

2

I'm not sure about EventValidation, but you can decode ViewState by using Fritz Onion's ViewState Decoder.

answered Jul 07 '09 at 14:43

Bob Mc

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Looks like Fritz pulled down the utility. A Google search pulls up this one first (http://ignatu.co.uk/ViewStateDecoder.aspx) but I cannot vouch for it. A shame really, Fritz' contribution was quite good. – Bob Mc Sep 22 '14 at 03:21

syntagma · Answer 3 · 2017-02-05T13:32:05.300

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I needed to decode ViewStates recently and found this tool useful: View State decoder

edited Feb 05 '17 at 13:32

answered Dec 25 '12 at 13:14

syntagma

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@mrGreenBrown Just fixed it. – syntagma Feb 05 '17 at 13:32

score 0 · Answer 4 · edited Sep 13 '11 at 21:28

0

Create a simple windows app and use Convert.FromBase64(str) to decode ViewState data if it is not encrypted.

Note: GridView causes encryption.

edited Sep 13 '11 at 21:28

Jérôme Verstrynge

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answered Mar 15 '11 at 10:44

smaildeveloper

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score 0 · Answer 5 · answered Aug 15 '20 at 03:58

You can use this link if use python.

Best way is use this link.

A small Python 3.5+ library for decoding ASP.NET viewstate.

First install that: pip install viewstate

>>> from viewstate import ViewState
>>> base64_encoded_viewstate = '/wEPBQVhYmNkZQ9nAgE='
>>> vs = ViewState(base64_encoded_viewstate)
>>> vs.decode()
('abcde', (True, 1))

Is it possible to decode EventValidation and ViewState in ASP.NET?

5 Answers5

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