This application is a graphical editor for SQLesque data filtering language. Since last sentence doesn't really tell much much here's a picture that should explain it much better:

Changes to filter string (top textbox) are propagated to filter tree (right pane) and vice versa. Transformation from filter tree works by parsing the expression using ANTLR, compiling using Expression Trees and binding resulted delegate to ListView's filter, AST generated by ANTLR is bound to right pane.

• Filtering is strongly-typed (represented by type Filter<T> where T is type of filtered object) and can filter only on properties marked with [Filterable] attribute.
• Keywords are upper-case, strings are delimited with single quotations, object properties can be delimited with double quotations or left as is.
• Filter tree (right pane) to filter string transformation does not preserve keywords, brackets, nor double quotations.
• WPF part of the project was written with flagrant disregard of MVVM and is quite crappy. I've learned better since then.