public static Perceived GetPerceivedType(string fileName)
{
if (fileName == null)
{
throw new ArgumentNullException(nameof(fileName));
}
var extension = Path.GetExtension(fileName);
if (extension == null)
{
throw new ArgumentException("The extension cannot be determined from the file name", nameof(fileName));
}
extension = extension.ToUpperInvariant();
if (s_perceivedTypes.TryGetValue(extension, out var ptype))
{
return(ptype);
}
if (!IsSupportedPlatform())
{
throw new PlatformNotSupportedException("PerceivedType is only supported on Windows");
}
lock (SyncObject)
{
var type = PerceivedType.Unknown;
var source = PerceivedTypeSource.Undefined;
if (!s_perceivedTypes.TryGetValue(extension, out ptype))
{
using (var key = Registry.ClassesRoot.OpenSubKey(extension, writable: false))
{
if (key != null)
{
var ct = key.GetStringValue("PerceivedType");
if (ct != null)
{
type = Extensions.GetEnumValue(ct, PerceivedType.Custom);
source = PerceivedTypeSource.SoftCoded;
}
else
{
ct = key.GetStringValue("Content Type");
if (ct != null)
{
var pos = ct.IndexOf('/', StringComparison.Ordinal);
if (pos > 0)
{
type = Extensions.GetEnumValue(ct.Substring(0, pos), PerceivedType.Custom);
source = PerceivedTypeSource.Mime;
}
}
}
}
}
if (type == PerceivedType.Unknown)
{
var text = IntPtr.Zero;
type = PerceivedType.Unknown;
source = PerceivedTypeSource.Undefined;
var hr = AssocGetPerceivedType(extension, ref type, ref source, ref text);
if (hr != 0)
{
type = PerceivedType.Unspecified;
source = PerceivedTypeSource.Undefined;
}
}
ptype = new Perceived(extension, type, source);
s_perceivedTypes.Add(extension, ptype);
}
return(ptype);
}
}