What is the purpose of __EVENTVALIDATION __VIEWSTATE in aspx
<pre><code>Content-Disposition: form-data; name="__VIEWSTATE"

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Content-Disposition: form-data; name="__EVENTVALIDATION"

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</code></pre>

<p>We make a site where users can upload photos.</p>

<p>Latter we decided that users can also upload photos via other apps and we like to have a uniform interface. So the other apps work with the same page.</p>

<p>We notice that we cannot upload photos unless we know the value of __EVENTVALIDATION and __VIEWSTATE</p>

<p>Of course the app can just load the uploading image but that's kind of a hassle.</p>

<p>What are those for anyway? Is there a way to upload images to aspx upload web without specifying things.</p>
