The same selection color is used to highlight selected cells and incremental search results. If you change SelectionAlphaBlend, you affect both parts.
The only workaround that came into my mind by this moment is to set SelectionAlphaBlend temporarily to 255 when the user starts typing to do incremental search and then back to the required value when incremental search has completed. Obviously, you can do that in key processing related events events like KeyPress. The hardest part of this work is to process all keys which change the search string (among them ESCAPE, BACKSPACE, etc).
I don't think we are talking about the same thing:
First, I select a cell in the grid to mark the column I want to search in. That cell gets highlighted with the selection color.
When I start typing, the incremental search moves the selection to the cell it find the text in, again with the selection color. But it also highlights the few letters i actually typed with white, so I can see the cell selection and the search-sub-string inside the selected cell.
Now I apply aplha-blending and do the same thing. What changes for me, is that the highlighting of the search-sub-string inside the cell is no longer visible.
The "white" backgroundcolor of the sub-string-display should be painted over the alpha-blended selected cell, just like it is when alpha-blending is off, it currently looks like it's painted below and gets overdrawn by the alpha-blended selection backcolor.
I actually thought about your workaround to change the alpha-blending on incremental search, but it seems difficult to catch that case correctly and especially change it back when no longer needed.
Regards,
Oliver