/// <summary>
/// Look up the preview handler associated with the file extension
/// </summary>
/// <returns></returns>
private PreviewHandlerInfo LookupPreviewHandler()
{
RegistrationData data = PreviewHandlerRegistryAccessor.LoadRegistrationInformation();
var extension = data.Extensions.FirstOrDefault(x => HasExtension(_filePath, x.Extension) && (x.Handler != null));
return(extension?.Handler);
}
/// <summary>
/// 1) Look up the preview handler associated with the file extension
/// 2) Create an instance of the handler using its CLSID and reflection
/// 3) Check if it is a file or stream handler
/// 4) Initialize with File or Stream using Initialize from the appropriate interface
/// 5) Call SetWindow passing in a handle to this control and the bounds of the control
/// 6) Call DoPreview
/// </summary>
private void GeneratePreview()
{
lblMessage.Visible = false;
if (_comInstance != null)
{
((IPreviewHandler)_comInstance).Unload();
}
RECT r;
r.top = 0;
r.bottom = this.Height;
r.left = 0;
r.right = this.Width;
RegistrationData data = PreviewHandlerRegistryAccessor.LoadRegistrationInformation();
PreviewHandlerInfo handler = null;
foreach (ExtensionInfo ei in data.Extensions)
{
if (_filePath.ToUpper().EndsWith(ei.Extension.ToUpper()))
{
handler = ei.Handler;
if (handler != null)
{
break;
}
}
}
if (handler == null)
{
lblMessage.Visible = true;
lblMessage.Text = "No Preview Available";
return;
}
Type comType = Type.GetTypeFromCLSID(new Guid(handler.ID));
try
{
// Create an instance of the preview handler
_comInstance = Activator.CreateInstance(comType);
// Check if it is a stream or file handler
if (_comInstance is IInitializeWithFile)
{
((IInitializeWithFile)_comInstance).Initialize(_filePath, 0);
}
else if (_comInstance is IInitializeWithStream)
{
if (File.Exists(_filePath))
{
StreamWrapper stream = new StreamWrapper(File.Open(_filePath, FileMode.Open));
((C4F.DevKit.PreviewHandler.PreviewHandlerFramework.IInitializeWithStream)_comInstance).Initialize(stream, 0);
}
else
{
throw new Exception("File not found");
}
}
((IPreviewHandler)_comInstance).SetWindow(this.Handle, ref r);
((IPreviewHandler)_comInstance).DoPreview();
}
catch (Exception ex)
{
_comInstance = null;
lblMessage.Visible = true;
lblMessage.Text = "Preview Generation Failed - " + ex.Message;
}
}