Let's say that ResourceFinder is in the namespace MyDllNameSpace.Images, the default namespace of your assembly (see Assembly properties) is MyDllNameSpace, the bmp should be into Images subfolder (so that ResourceFinder namespace is equal to default namespace + bmp folder): ToolboxBitmap(typeof(ResourceFinder), "ProgressBar.bmp")] free .net reporting and gdi+ tools www.neodatatype.net