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Editorial Team
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Asked: 2026-05-21T18:33:07+00:00

I have a NET 2.0 Winforms app based partly on this code . It

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I have a NET 2.0 Winforms app based partly on this code. It features a form transparency using UpdateLayeredWindow API. It works perfectly on Vista and Windows 7 but fails on Windows XP.

I have narrowed it down to UpdateLayeredWindow failing with last error 8 (not enough memory). While experimenting I also found out that swapping (desired) ULW_ALPHA for either ULW_COLORKEY or ULW_OPAQUE works on XP but produces the wrong effect (the image shows but the transparency is wrong).

I am wondering if something is wrong the way PNG bitmap is being loaded and handled by NET internally and that there is something about it UpdateLayeredWindow dislikes.

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1 Answer

  1. Editorial Team

    Looks like it’s working, but the layered windows are not actually visible, I guess the opacity settings are wrong. With the code you linked to, changing line 67 in LayeredForm.cs from “BlendOp = 255” to “BlendOp = 0” fixes the issue for me (running on Windows XP SP3).

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