private string GetFileTypeDescription(string fileName)
{
if (string.IsNullOrEmpty(fileName))
throw new ArgumentException("Argument 'fileName' cannot be null or empty.");
// Get the file extension in the form of ".doc" or ".xls"
string extension = Path.GetExtension(fileName);
// If there is no file extension, Windows Explorer just shows "File"
if (string.IsNullOrEmpty(extension))
return "File";
// Get the upper case version, without the ".". So ".doc" turns into DOC. This is used for unknown file types. This is how
// Windows Explorer shows unknown file types
string extensionNoDot = extension.Substring(1, extension.Length - 1).ToUpper();
// Go look up the extension in HKEY_CLASSES_ROOT
RegistryKey extensionKey = Registry.ClassesRoot.OpenSubKey(extension);
// If this is null, the file extension isn't registered, so just return the extension in caps, without the . - and " file". So
// somefile.pdb turns into "PDB file"
if (extensionKey == null)
return extensionNoDot + " file";
// The root/default value for a registry sub-key should have the ProgId of the application that is used to open the file - so
// go try to get that value.
string lookupProgId = extensionKey.GetValue("", string.Empty).ToString();
// If there is no default value, there is no application associated with the file extension.
if (string.IsNullOrEmpty(extension))
return extensionNoDot + " file"; ;
// Go lookup the progid
RegistryKey progIdKey = Registry.ClassesRoot.OpenSubKey(lookupProgId);
// If the progid wasn't found, then show the default value.
if (string.IsNullOrEmpty(extension))
return extensionNoDot + " file"; ;
// If we got here, the root/default value of the progid key should have the friendly name of the application, so return that.
// But again, if there was an error or if it's empty, it defaults to the standard "EXT file" format.
return progIdKey.GetValue("", extensionNoDot + " file").ToString();
}
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