Check which version of DirectX is installed

Question

As per the title, how can I check which version of DirectX a user has installed? Checking the FeatureLevel isn't enough, as my application can run on feature level 10.0, but requires that DirectX 11.1 be installed.

Why this is not a duplicate:

• How to code to get direct X version on my machine in C#?
  • The first answer in this question says "If Windows 7, DirectX = 11, if Windows Vista, DirectX = 10". This is wrong, as Vista supports both DirectX 10 and 11 and Windows 7 supports DirectX 11 and 11.1.
  • The second answer references a registry key which only applies to DirectX 9 and lower. Even on a Windows 7 system with DirectX 11.1 installed, this registry key will never indicate an installed version greater than 9.0c
• .NET How to detect if DirectX 10 is supported?
  • The answer to this question yet again references the same registry key for DirectX 9 and lower ONLY.

I need an answer that applies to DirectX 10 installs and up. That means determining if their version is 10, 10.1, 11 or 11.1.

Answer 1

EDIT: Removed registry check method because it works only for Dx <=9 (thx @Telanor)

This method is very, very slow, but only one I figured out that is 100% accurate

private static int checkdxversion_dxdiag()
{
    Process.Start("dxdiag", "/x dxv.xml");
    while (!File.Exists("dxv.xml"))
        Thread.Sleep(1000);
    XmlDocument doc = new XmlDocument();
    doc.Load("dxv.xml");
    XmlNode dxd = doc.SelectSingleNode("//DxDiag");
    XmlNode dxv = dxd.SelectSingleNode("//DirectXVersion");

    return Convert.ToInt32(dxv.InnerText.Split(' ')[1]);
}