How to get around the command line length limit?

If you want to drop files with respect of Windows Explorer, then you can implement your own Drop Handlers as a Shell Extension Handlers see:

• How to Create Drop Handlers (Windows)
• Creating Shell Extension Handlers

On The Complete Idiot's Guide to Writing Shell Extensions you will find a good introduction how to write such extensions.

The part VI gives an example of Drop Handler (for a little other use case, but it dose not matter).

With respect of Drop Shell Extension Handler your program will receive full information about all dropped files and you need not start a child program with all the files as command like parameters.

From this blog:

• The maximum command line length for the CreateProcess function is 32767 characters. This limitation comes from the UNICODE_STRING structure.
• If you are using the CMD.EXE command processor, then you are also subject to the 8192 character command line length limit imposed by CMD.EXE.
• If you are using the ShellExecute/Ex function, then you become subject to the INTERNET_MAX_URL_LENGTH (around 2048) command line length limit imposed by the ShellExecute/Ex functions.
• The maximum size of your environment is 32767 characters. The size of the environment includes all the variable names plus all the values.

So you're gonna have to settle with some of the mentioned workarounds (also, there's another workaround on the msdn blog I linked).

I think the drag and drop handler is possibly one way to go, but it seems quite heavy.

An alternative solution is to use a Explorer Context Menu handler. With this in place, you would select all the files, but rather than dragging them, right click, and choose your new menu item "Send to ".

When the menu item is selected, it passes the list of commands to your program. There are a couple of ways of doing this:

1. launch your program, and feed the list of files to standard input
2. write the list of files to a temporary file, and launch your program with just one command argument - the temporary file listing the files to process. List files are usually prefixed with '@' on the command line to distinguish them from ordinary file names.