C# - GetMimeType

GetMimeType.cs

static string GetMimeType(string fileName)
{
    string mimeType = "application/unknown";
    string ext = Path.GetExtension(fileName).ToLower();
Microsoft.Win32.RegistryKey regKey = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(ext);
    if (regKey != null && regKey.GetValue("Content Type") != null)
    {
        mimeType = regKey.GetValue("Content Type").ToString();
    }
    else if (ext == ".png")
    {
        mimeType = "image/png";
    }
    return mimeType;
}