Thinking in C# phần 6

bảng dữ liệu quan hệ và XML) cũng như làm cho nó dễ dàng hơn nhiều chương trình ứng dụng cơ sở dữ liệu widelydistributed. Tuy nhiên, mô hình này làm tăng khả năng hai người sử dụng sẽ làm cho thay đổi không phù hợp với các dữ liệu liên quan, họ sẽ dự trữ cả hai ghế cuối cùng trên chuyến bay, người ta sẽ đánh dấu một vấn đề như giải quyết trong khi khác sẽ mở rộng phạm vi của cuộc điều tra. Vì vậy, ngay cả một giới thiệu tối thiểu để đòi hỏi. | relational table data and XML as well as making it much easier to program widely-distributed database applications. However this model increases the possibility that two users will make incompatible modifications to related data - they ll both reserve the last seat on the flight one will mark an issue as resolved while the other will expand the scope of the investigation etc. So even a minimal introduction to requires some discussion of the issues of concurrency violations. Getting a handle on data with DataSet The DataSet class is the root of a relational view of data. A DataSet has DataTables which have DataColumns that define the types in DataRows. The relational database model was introduced by Edgar F. Codd in the early 1970s. The concept of tables storing data in rows in strongly-typed columns may seem to be the very definition of what a database is but Codd s formalization of these concepts and others such such as normalization a process by which redundant data is eliminated and thereby ensuring the correctness and consistency of edits was one of the great landmarks in the history of computer science. While normally one creates a DataSet based on existing data it s possible to create one from scratch as this example shows c10 using System using class BasicDataSetOperations public static void Main string args DataSet ds BuildDataSet PrintDataSetCharacteristics ds private static DataSet BuildDataSet DataSet ds new DataSet MockDataSet DataTable auTable new DataTable Authors auTable DataColumn nameCol new DataColumn Name typeof string nameCol DataRow larryRow 422 Thinking in C larryRow Name Larry larryRow DataRow bruceRow bruceRow Name Bruce bruceRow return ds private static void PrintDataSetCharacteristics DataSet ds DataSet 0 has 1 tables foreach .