What is the simplest way for VBA code (in Excel) to send some sort of signal to a .NET process and tell it to do something? The VBA code knows the task ID of the .NET process, because it started that process (a Windows Forms app) using Shell(). It isn't necessary to pass any information either way (although that wouldn't hurt); all that is needed is a way to poke at the .NET process so that it wakes up and looks for an instruction file that has just been written by Excel.
Right now the .NET process is polling the disk, looking for new instruction files. This actually works fine, but since there can be long intervals between new instruction files, it would be better if there were some way for Excel to notify the .NET process directly when a new file is written. I'm sure there's a way to do this using sockets and threads, but I'd like to add as little complexity as possible, so if anyone knows a simpler way I hope you will let me know about it. -- John Brock jbr...@panix.com
John Brock wrote: > What is the simplest way for VBA code (in Excel) to send some sort > of signal to a .NET process and tell it to do something? The VBA > code knows the task ID of the .NET process, because it started that > process (a Windows Forms app) using Shell(). It isn't necessary > to pass any information either way (although that wouldn't hurt); > all that is needed is a way to poke at the .NET process so that it > wakes up and looks for an instruction file that has just been > written by Excel.
> Right now the .NET process is polling the disk, looking for new > instruction files. This actually works fine, but since there can > be long intervals between new instruction files, it would be better > if there were some way for Excel to notify the .NET process directly > when a new file is written. I'm sure there's a way to do this > using sockets and threads, but I'd like to add as little complexity > as possible, so if anyone knows a simpler way I hope you will let > me know about it.
How is the .Net process polling, currently? If you are just testing for a file existence, then I think you should try FileSystemWatcher on the .net side.
I'm sure there is a way for Excel to signal the external app, but the process sound more or less independent.
>John Brock wrote: >> What is the simplest way for VBA code (in Excel) to send some sort >> of signal to a .NET process and tell it to do something? The VBA >> code knows the task ID of the .NET process, because it started that >> process (a Windows Forms app) using Shell(). It isn't necessary >> to pass any information either way (although that wouldn't hurt); >> all that is needed is a way to poke at the .NET process so that it >> wakes up and looks for an instruction file that has just been >> written by Excel.
>> Right now the .NET process is polling the disk, looking for new >> instruction files. This actually works fine, but since there can >> be long intervals between new instruction files, it would be better >> if there were some way for Excel to notify the .NET process directly >> when a new file is written. I'm sure there's a way to do this >> using sockets and threads, but I'd like to add as little complexity >> as possible, so if anyone knows a simpler way I hope you will let >> me know about it. >How is the .Net process polling, currently? If you are just testing for >a file existence, then I think you should try FileSystemWatcher on the >.net side.
>I'm sure there is a way for Excel to signal the external app, but the >process sound more or less independent.
Definitely an improvement! (And it probably would have taken me hours of plowing through the .NET documentation before I stumbled across that class, so thanks!).
Unfortunately the sequence of events the .NET process receives from FileSystemWatcher varies -- in a not always intuitive way -- depending to how the watched file is updated. (E.g., if I create the file using "Save As..." in Notepad the sequence is Created, Deleted, Created, Changed, Changed). This makes it difficult for me to determine in a completely general way when the file is ready to be read.
I can get around this of course by writing the file under a different name and then renaming it. I'm still hoping though to find some easy way to use the task ID to directly signal the .NET process from Excel, or even pass it a string. But if I can't then FileSystemWatcher it is. -- John Brock jbr...@panix.com
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