public static IPreviewHelper Create(
string extension,
List <IPreviewHelper> previewAppDescriptions
)
{
IPreviewHelper appDescription = null;
string lowPointlessExt = extension.ToLower().Replace(@".", string.Empty);
foreach (var previewAppDescription in previewAppDescriptions)
{
foreach (var ext in previewAppDescription.Extensions)
{
if (lowPointlessExt == ext)
{
appDescription = previewAppDescription;
break;
}
}
if (appDescription != null)
{
break;
}
}
return(appDescription);
}
/// <summary>
/// Opens the specified file using the appropriate preview handler and displays the result in this PreviewHandlerHost.
/// </summary>
/// <param name="filename"></param>
/// <returns></returns>
public override bool Open(string filename)
{
_appDescription = PreviewAppDescriptionFactory.Create(
Path.GetExtension(filename),
PreviewAppDescriptions
);
if (_appDescription != null)
{
_appDescription.Startup();
}
UnloadPreviewHandler();
if (String.IsNullOrEmpty(filename))
{
ErrorMessage = Messages.FileNotLoaded;
return(false);
}
// try to get GUID for the preview handler
Guid guid = GetPreviewHandlerGUID(filename);
ErrorMessage = "";
if (guid != Guid.Empty)
{
try
{
if (guid != _currentPreviewHandlerGuid)
{
_currentPreviewHandlerGuid = guid;
// need to instantiate a different COM type (file format has changed)
if (_currentPreviewHandler != null)
{
Marshal.FinalReleaseComObject(_currentPreviewHandler);
}
// use reflection to instantiate the preview handler type
Type comType = Type.GetTypeFromCLSID(_currentPreviewHandlerGuid);
_currentPreviewHandler = Activator.CreateInstance(comType);
}
if (_currentPreviewHandler is IInitializeWithFile)
{
// some handlers accept a filename
((IInitializeWithFile)_currentPreviewHandler).Initialize(filename, 0);
}
else if (_currentPreviewHandler is IInitializeWithStream)
{
if (File.Exists(filename))
{
// other handlers want an IStream (in this case, a file stream)
_currentPreviewHandlerStream = File.Open(filename, FileMode.Open);
StreamWrapper stream = new StreamWrapper(_currentPreviewHandlerStream);
((IInitializeWithStream)_currentPreviewHandler).Initialize(stream, 0);
}
else
{
ErrorMessage = Messages.FileNotFound;
}
}
if (_currentPreviewHandler is IPreviewHandler)
{
// bind the preview handler to the control's bounds and preview the content
Rectangle r = ClientRectangle;
((IPreviewHandler)_currentPreviewHandler).SetWindow(Handle, ref r);
((IPreviewHandler)_currentPreviewHandler).DoPreview();
return(true);
}
}
catch (Exception ex)
{
ErrorMessage = Messages.PreviewError + ":\n" + ex.Message;
}
}
else
{
ErrorMessage = Messages.NoPreviewAvailable;
}
return(false);
}
