URL decoding not working as expected

My Browser shows URL with file name as

http://www.example.com/pdf/204177_20090604_Chloorhexidine_DCB_oogdruppels_0%2C1%25.pdf

Act开发者_开发百科ual File name is 204160_20090604_Atropine_DCB_oogdruppels_0,5%.pdf

After urldecode, it gives wrong file name as http://www.example.com/pdf/204177_20090604_Chloorhexidine_DCB_oogdruppels_0,1%.pdf

Update:

Initially I thought that its problem of URL Decode, but files like name 204153_20090605_Aluminiumacetotartraat_DCB_oordruppels_1,2%.pdf while rendering in browser throws Bad request. I am using Kohana 3 framwork. Is it related with server?

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$url = 'http://204160_20090604_Atropine_DCB_oogdruppels_0,5%.pdf';
$encode = urlencode($url);
$decode = urldecode($encode);

echo $url."<br />";
echo $encode."<br />";
echo $decode."<br />";

// outputs
http://204160_20090604_Atropine_DCB_oogdruppels_0,5%.pdf
http%3A%2F%2F204160_20090604_Atropine_DCB_oogdruppels_0%2C5%25.pdf
http://204160_20090604_Atropine_DCB_oogdruppels_0,5%.pdf

All ok. You're error is somewhere else.

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You are looking at two different files.

It's not possible to urlencode 204160_20090604_Atropine_DCB_oogdruppels_ into 204177_20090604_Chloorhexidine_DCB_oogdruppels_, encoding does not change alphabetical characters.

The error is most likely in the code that creates the file list and outputs the links; the mapping between link titles and filenames appears to be messed up.

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this will give you exact file name m using c#

Server.UrlDecode("http://www.example.com/pdf/204160_20090604_Atropine_DCB_oogdruppels_0,5%25.pdf")

, (comma) is encoded as %2c % (percent) is encoded as %25 by browsers

if you use Request.Url it'll decode ,(comma) but not %(percent)

So Server.UrlDecode("xyz") decode all characters except %(percent), thats y there's "%25" in the above filename