"Ugly Red X" and Virtual Grid

[Administrator]

I am using (trying to use) a virtual grid using an ArrayList with custom objects in the array. The array is rather large (2000-3000 elements).
The virtual grid is responding to the required events (QueryRowCount, QueryCellInfo, etc.) and the grid is painting just fine - all the events are firing and I am responding correctly to the "painting" events. In fact, everything is great when I use the arrow keys to move up and down the grid - painting is quick and reliable! However, within say 5-10 mouse clicks on the grid (it varies) my evil friend the "Ugly Red X" appears inside the grid boundaries. I can scroll up and down with the keyboard all day, but as soon as I start activating cells with the mouse all heck breaks out. What gives? Any silver bullets?

[Administrator]

Are you using multiple threads?

If so, you must protect calls into grid methods using grid.InvokeRequired checks. Not doing so is a typical cause of th ebehavior you described. Here is a KB discussing this problem. http://www.syncfusion.com/Support/article.aspx?id=572

If you are not using multiple threads, then I am not sure what might be causing this behavior. The red x suggest that an exception is being thrown during the Paint. You can set the debugger to stop on exception and try to see if the call stack may give some clue. If you own the source code version, you can use the AssemblyManager to build a debug version and actually step into our code around any exception.

[Administrator]

Thanks for your quick response Clay.

No, I am not using multiple threads and yes I do have the source code for EssentialGrid. I will use Assembly Manager as you suggest and see if I can spot where the exception is happening. Thanks.

>Are you using multiple threads?
>
>If so, you must protect calls into grid methods using grid.InvokeRequired checks. Not doing so is a typical cause of th ebehavior you described. Here is a KB discussing this problem. http://www.syncfusion.com/Support/article.aspx?id=572
>
>If you are not using multiple threads, then I am not sure what might be causing this behavior. The red x suggest that an exception is being thrown during the Paint. You can set the debugger to stop on exception and try to see if the call stack may give some clue. If you own the source code version, you can use the AssemblyManager to build a debug version and actually step into our code around any exception.

[Administrator]

Voila!!!

Problems solved. Debug suggested that my index back into my ArrayList was throwing an exception - index was out of range. I am not checking for any e.RowIndex<0.

Question: Why would the grid try and pass me a bad record index to my QueryCellInfo, and secondly, why is this behavior different for keyboard operations and mouse operations?

>Thanks for your quick response Clay.
>
>No, I am not using multiple threads and yes I do have the source code for EssentialGrid. I will use Assembly Manager as you suggest and see if I can spot where the exception is happening. Thanks.
>
>>Are you using multiple threads?
>>
>>If so, you must protect calls into grid methods using grid.InvokeRequired checks. Not doing so is a typical cause of th ebehavior you described. Here is a KB discussing this problem. http://www.syncfusion.com/Support/article.aspx?id=572
>>
>>If you are not using multiple threads, then I am not sure what might be causing this behavior. The red x suggest that an exception is being thrown during the Paint. You can set the debugger to stop on exception and try to see if the call stack may give some clue. If you own the source code version, you can use the AssemblyManager to build a debug version and actually step into our code around any exception.

[Simon Spruzen]

I''ve seen this too. I believe for a virtual grid, a row and/or col index of -1 indicates that the ''global'' style is required (i.e. the default for the grid not for a cell.). Just filter it out: 0 = header, 1..n = your data index + 1.
Works well.

[Administrator]

e.ColIndex = -1 and e.RowIndex > 0 is a request for a rowstyle. The opposite situation is a request for column styles.