Implementation Of Object/Relational Mapping In .NET Environment

Object-oriented program is the most popular software-design method nowadays. The relational database is the main saving mechanism. This paper compares the object model with the relation model in data management. The object model is based on the software development, and the the relation model is based on mathematics theory. The differences lead to the problem of 'Impedance Mismatch'. This paper analyzes object/relation mapping's existent problem, namely object identifier technique and mapping object to relation technique etc, proposes the strategy of object/relation mapping, designs and implements a persistent layer base on O/R Mapping-ORM4NET, analyzes and improves the select method in object/relation mapping.The persistent layer-ORM4NET has some kind of characteristics:(1)Proposes the 'delay loading' method to solve the problem of waste of memory, achieves the purpose of on-demanding loading.(2)Uses the mapping method based on .NET metadata, mixes the persistent object with the configure information, reduces the code, increases the expansibility.(3)Supports generating the OID automaticly, conveniences the development of program.(4)Supports directly access the database, provides many kings of data access method.This paper brings good results in the field of persistent-layer design. And the persistent layer has found wide application in project.