If you are getting licensing exceptions associated with the WPF Property Grid, please read this FAQ. If it doesn't solve your problem, post in the forum and we will work with you to resolve the problem.
The most common causes of licensing exceptions, and how to solve them, are as follows (in no particular order!):
1. The licence file is not present alongside the WPF Property Grid DLL. This can happen if you are referencing the DLL at a location other than the install location -- e.g. if you have copied it to a project Lib directory. SOLUTION: Copy the .lic file from the install folder to the reference location.
2. Your project does not include a licenses.licx file, or the build settings for licenses.licx are not correct. Visual Studio is meant to create this file when you add a licensed control to your project, but the WPF designer doesn't always seem to do it (especially when adding controls through the XAML text editor). SOLUTION: Copy licenses.licx from one of the samples to your project's Properties folder, include it in the project, and set the build action to Embedded Resource.
3. The project which references the WPF Property Grid is a Class Library (DLL) project, and this DLL is used in an application (EXE) project. The EXE project must *also* have a reference to the grid DLL, *and* must have a licenses.licx file with the appropriate build settings (as in #2). SOLUTION: In your EXE project, add a reference to Mindscape.WpfPropertyGrid.dll. Then copy licenses.licx from one of the samples to your EXE project's Properties folder, include it in the project, and set the build action to Embedded Resource.
4. You have a trial licence and it has expired. In this case you should see a message box telling you about the problem, and you will get the error at compile time instead of runtime. SOLUTION: Purchase the retail version! If you need to extend your trial licence, for example to complete your evaluation or because there is a delay in the purchasing process, get in touch via the contact form.
5. There is another version of the control in the GAC. Open an Explorer window on C:\Windows\Assembly and see if it contains Mindscape.WpfPropertyGrid.dll. SOLUTION: Remove the copy in the GAC (right-click and choose Uninstall).