I updated my forum but the bugfix for Edge was just a replace of the bug by 1 => "Select all" just select one line..

So here is my bugfix :
In prosilver Template directory, the forum_fn.js file.

The function in 3.1.6 Prosilver Template :
function selectCode(a) {
2. 'use strict';
3.
4. // Get ID of code block
5. var e = a.parentNode.parentNode.getElementsByTagName('CODE')[0];
6. var s, r;
7.
8. // Not IE and IE9+
9. if (window.getSelection) {
10. s = window.getSelection();
11. // Safari and Chrome
12. if (s.setBaseAndExtent) {
13. var l = (e.innerText.length > 1) ? e.innerText.length - 1 : 1;
14. try

{ 15. s.setBaseAndExtent(e, 0, e, l); 16. }

catch (error)

{ 17. s.setBaseAndExtent(e, 0, e, 1); 18. }

19. }
20. // Firefox and Opera
21. else {
22. // workaround for bug # 42885
23. if (window.opera && e.innerHTML.substring(e.innerHTML.length - 4) === '<BR>')

{ 24. e.innerHTML = e.innerHTML + ' '; 25. }

26.
27. r = document.createRange();
28. r.selectNodeContents(e);
29. s.removeAllRanges();
30. s.addRange(r);
31. }
32. }
33. // Some older browsers
34. else if (document.getSelection)

{ 35. s = document.getSelection(); 36. r = document.createRange(); 37. r.selectNodeContents(e); 38. s.removeAllRanges(); 39. s.addRange(r); 40. }

41. // IE
42. else if (document.selection)

{ 43. r = document.body.createTextRange(); 44. r.moveToElementText(e); 45. r.select(); 46. }

47.}

Just replace line 17 "s.setBaseAndExtent(e, 0, e, 1);"
by :
r = document.createRange();
r.selectNodeContents(e);
s.removeAllRanges();
s.addRange(r);

And voilà !