I'm currently working on a map editor in C#. I decided to port it from Visual C# Express 2005 Beta to Visual Studio .NET 2003, since Visual C# Express Beta is quite bugged and requires Framework 2.0... So, everything was working great, up to the point where I added my DirectX drawing method ( with Device.DrawPrimitives ).. First of all, I always have an very vague exception occuring during this function call. Exception source: Microsoft.DirectX.Direct3D Stack: at Microsoft.DirectX.Direct3D.Device.DrawPrimitives(PrimitiveType...) I have also a game in C# which works fine in Visual Studio .NET 2003 using pretty much the same drawing code.. I don't get why this one don't work. And even though there's an exception occuring, the triangles are still drawn properly. Also, it seems that into my Map Editor solution, "CustomVertex" is not properly recognized by Intellisense.. When I type "CustomVertex.", the box pop-up with only 2 choices: "Equals" and "ReferenceEquals".. There's not any of the "TransformedColored", "PositionTextured", etc. In my other game project in C#, still in Visual Studio 2003 .NET, CustomVertex is recognized without any problem. I have october 2004 DirectX SDK.. I verified, there's no typos in my code where I want to use CustomVertex. (No braces missing, or anything which would confuse Intellisense, since anyway anything else I type at the same place instead of CustomVertex will be properly completed with Intellisense..) Any idea how could I fix that? Thanks a lot.