An appropriate approach for integrating UML and B specification techniques allows us to map UML specifications into B specifications. Therefore, we can formally analyze an UML specification via the corresponding B formal specification. This point is significant because B support tools are available. We can also use UML specifications as a tool for building B specifications. Thus, an approach for a practical and rigorous software development, which is based on object and B from the requirements elicitation to the executable code, is proposed. In this paper, we address the problem of modeling UML behavioral diagrams in B, which is up to now an open issue. For this purpose, an approach for modeling in B class operations is proposed. We show a way to apply this approach for integrating collaboration diagrams into B specifications.