||In the past 20 years, lots of approaches to query database were developed. In the industry nowadays, ADO.NET is considered to be the most convenient and practical technology, because it can be compatible with a variety of data sources. Meanwhile, Object-Oriented Programming (OOP) continues to be a stable and popular technology of software development. Some people even believe that it was a mistake for the database research community in the 1970s to focus on data sub-languages that could be embedded in any programming language, rather than adding high-level data access to all programming languages. Thus, a major challenge - how to access and integrate information from databases - confronts many programmers and will likely increase in the future. .NET Language Integrated Query (LINQ) technology is emerging as a good solution to this problem. The paper mainly includes two parts. First, we briefly discuss both techniques' origin and background. After the introduction, we will explain how to use them to query by LINQPad, which is a very handy tool and is like a lightweight SQL Management Studio. We will use it to elaborate the expressions in ADO.NET and LINQ to SQL and then compare them with respect to their functions. In particular, we will focus on the significant differences in aggregate functions in the two techniques. Second, we present our benchmark consisting of eight tasks that we use to compare the performance of ADO.NET and its successor LINQ to SQL. We will work on the actual IMDB database as our test database. The end of the paper will conclude the features of ADO.NET and LINQ to SQL, and the analysis of their efficiency as well.