Get syntax coloring with Prism on object tag with external source?

Question

I used to have syntax coloring on code blocks using Prism.js like this:

<code class="language-cs">{code}</code>

I'm now trying to load source files using the object-tag instead like this:

<code class="language-cs">
  <object type="text/plain" data="{url}">
</code>

This does not work, but loads the text without syntax coloring.

Any idea how to solve this?