Parameters passed on URL line

I am passing parameters to another page on the URL line (ie. somepage.aspx?parm1=value1&parm2=value2). I observed that when running in Visual Studio environment the values are passed in upper case while running in the Browser they are in lower case. The same code was run in both cases. Of course, when case matters, the code would fail. Can anyone explain this phenomena and a possible solution of retaining the original case?
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