1. Required Slide Data Access Best Practices Gieno Miao

2. Session Objectives / Agenda Connection Optimizations Best Practices on DataSets & DataViews Best Practices on DataReaders DataSets vs. DataReaders Using Command Objects Efficiently Choosing the Right Command Execution Transactions Database Level Optimizations Security Best Practices Best Ways to Access XML Data

3. 1. Connection Optimizations Open Late & Close Early Use the Correct Provider SqlClient OleDb ODBC Others Take Advantage of Connection Pooling Use Same Credentials in Connection Strings Design connections for groups/roles, not users Be aware of objects that manage connections

4. 2. Best Practices when using DataSets & DataViews DataSets Using Strongly Typed DataSets Filling Best Practices Getting Data from Multiple Sources: Use DataSets Most Efficient Ways to Search Through DataSets Considerations for using DataViews // Untyped Dataset string empName = employeesData.Tables["Employees"].Rows[0]["EmployeeName"].ToString(); // Strongly Typed DataSet string empName = employeesData.Employees[0].CompanyName;

5. 3. Best Practices when using DataReaders DataReaders Row Level Optimizations Speed/Efficiency Best Practices When to Close DataReaders What to do when cancelling data reads Thread myThread2 = new Thread(new ThreadStart(Thread_Cancel)); myThread2.Start(); myThread2.Join(); reader.Read(); readerLabel.Text = (reader.FieldCount.ToString()); reader.Close(); public static void Thread_Cancel() { Command.Cancel(); }

6. 4. DataSets vs. DataReaders When to use DataSets vs. DataReaders Flexibility vs. Speed Paging Through Data DataSets vs. DataReaders Use ROW_NUMBER() in SQL 2005

7. 5. Using Command Objects Efficiently Query Performance Best Practice Techniques CommandType Parameter Data Types Using Add Method (with full overloads) - instead of AddWithValue Preferred cmd.Parameters.Add("@EmployeeID", SqlDbType.Int, 4).Value = empId ; Don’t Use command.Parameters.AddWithValue("@EmployeeId", empId); Deprecated cmd.Parameters.Add("@EmployeeID", empId);

8. 5. Using Command Objects Efficiently Command Object vs. CommandBuilder Choosing the Right Execution Method When to Use ExecuteNonQuery When to Use ExecuteScalar When to Use ExecuteReader

9. 6. Transactions Best Way to Design Transactions Short and Sweet As Close to DB as Possible Use Read Committed Isolation Level for most Apps (SQL Default/ADO.NET Default)

10. 7. Database Level Best Practices Storing Data Correctly Correct Data Types and Lengths Correct Defaults and Constraints Using Primary and Foreign Keys Avoiding Triggers for Referential Integrity Benefits of Using Stored Procedures Performance Security Maintenance

11. 8. Database Level Best Practices Indexes How Indexes Optimize Data Access What Columns Should be Indexed? Writing the Most Efficient Queries

12. 9. Security Best Practices Securing via Stored Procedures (and objects) Storing Connection Strings Securely Using Low Privilege Accounts Why to Avoid Using System Admin Accounts

13. 10. XML Data Retrieval Best Practices XMLDocument vs XMLDataDocument XMLReader vs XMLTextReader vs XMLValidatingReader Using LINQ to XML var custs = from c in XElement.Load("Customers.xml").Elements("Customers") select c ; foreach (var customer in custs) { Console.WriteLine(customer); } Dim cust As XElement = _ New XElement("Customers", _ From cust In Customers _ Select New XElement("Customer", _ New XAttribute("Name", cust.Name), _ New XAttribute("TotalSales", cust.TotalSales)))