Hi all,
I have been working on a project which was till now in unmanaged C and C++.
We have been trying to port the front end only to c# while retaining the backend in unmanaged c and c++.
To do that, we have converted the backend into a dll and call it using P/Invoke.
The code updates a listview dynamically but the earlier listview was in unmanaged.
Now here's the weird part. The function which takes the listview handle and updates it uses sendmessage to do that as below:



I am calling this from managed code as this:


After the execution is done, I can see that the listview is updated (all the fields are correctly set) but the count of the items is still 0. When I try and click on the listview, the application throws an ArgumentOutOfRangeException saying that the index is invalid.

This has been driving me mad. Can any one please tell me what am I doing wrong here?

Thanks.

This post has been edited by achintya: 20 May, 2008 - 03:38 PM

can you post your unmanaged code that raps your dll. That is the code that matters your c and c++ methods you just need to know the parameters and return type.

The parameters and return type have no role here. What I did was to create a test project to test this problem and have posted the code in the previous post. Anyway, I could illustrate the problem a bit more here I guess.



Now I tried something really simple. I created an unmanaged project and just wrote a simple function to update the list view.



I am calling this ofcourse as mentioned earlier, ie passing the handle of the listview control.

This sets my listview properly and I can see all the items in the UI. But as soon as I click on it, or do a slight drag, it throws an ArgumentOutOfRangeException.
Upon debugging, I found that after the unmanaged code has finished executing, the count of items in the listview still remains 0! How is this possible? I can see the bloody items in the UI, so why aren't they showing up in the count!

This has driven me nuts and now I am contemplating passing delegates to just get the values from the unmanaged code and update the list view myself in the managed code. But this would involve a major rewrite of the functions.

I suppose that the underlying architecture of all the controls should be the same, and any message sent to an unmanaged or managed code should do just fine. However, I may be wrong, and it certainly looks like the case
Help!!

what is LVITEM is this a struct when you wrap [DllImport("unmanaged.dll") do you have handle returned meaning you use the ref key work to return a handle to your dll

Example:


then your managed code looks like this



now you will have the handle to you c++ code and your code uptop