Scan&Store Solution

Question

Does anyone have a solution for Web Scan&Store module. For Win Application i used Twain Interface.

Lalit M · Answer

First step was to port the most important parts of TWAIN.H  these are found in TwainDefs.cs . The real logic for calling TWAIN is coded in the class Twain  in file TwainLib.cs. . As the TWAIN API is exposed by the Windows DLL twain_32.dll  we have to use the .NET DllImport mechanism for interop with legacy code. This DLL has the central DSM_Entry()  ordinal #1 function exported as the entry point to TWAIN. This call has numerous parameters and the last one is of variable type! It was found to be best if we declare multiple variants of the call like: [DllImport(twain_32.dll EntryPoint=#1)] private static extern TwRC DSMparent( [In Out] TwIdentity origin IntPtr zeroptr TwDG dg TwDAT dat TwMSG msg ref IntPtr refptr ); The Twain class has a simple 5-step interface: class Twain { Init(); Select(); Acquire(); PassMessage(); TransferPictures(); } For some sort of 'callbacks' TWAIN uses special Windows messages and these must be caught from the application-message-loop. In .NET the only way found was IMessageFilter.PreFilterMessage()  and this filter has to be activated with a call like Application.AddMessageFilter() . Within the filter method we have to forward each message to Twain.PassMessage()  and we get a hint ( enum TwainCommand ) back for how we have to react. you can download code sample just few details register