ptg 764 CHAPTER 17 Building Components newProduct.Save(); } /// <summary> /// Deletes an existing product /// </summary> /// <param name=”id”>Product Id</param> public static void Delete(int id) { if (id < 1) throw new ArgumentException(“Product Id must be greater than 0”, ➥ “id”); SqlDataAccessLayer dataAccessLayer = new SqlDataAccessLayer(); dataAccessLayer.ProductDelete(id); } /// <summary> /// Validates product information before saving product /// properties to the database /// </summary> private void Save() { if (String.IsNullOrEmpty(_name)) throw new ArgumentException(“Product Name not supplied”, “name”); if (_name.Length > 50) throw new ArgumentException(“Product Name must be less than 50 characters”, “name”); if (String.IsNullOrEmpty(_description)) throw new ArgumentException(“Product Description not supplied”, “description”); SqlDataAccessLayer dataAccessLayer = new SqlDataAccessLayer(); if (_id > 0) dataAccessLayer.ProductUpdate(this); else dataAccessLayer.ProductInsert(this); } /// <summary> /// Initializes Product /// </summary> /// <param name=”name”>Product Name</param> /// <param name=”price”>Product Price</param> /// <param name=”description”>Product Description</param> public Product(string name, decimal price, string description) From the Library of Wow! eBook ptg 765 Architectural Considerations 17 : this(0, name, price, description) { } /// <summary> /// Initializes Product /// </summary> /// <param name=”id”>Product Id</param> /// <param name=”name”>Product Name</param> /// <param name=”price”>Product Price</param> /// <param name=”description”>Product Description</param> public Product(int id, string name, decimal price, string description) { _id = id; _name = name; _price = price; _description = description; } } } The Product component contains four public methods named SelectAll(), Update(), Insert(), and Delete(). All four of these methods use the SqlDataAccessLayer compo- nent to interact with the Products database table. The SqlDataAccessLayer is contained in the Data Access layer. For example, the SelectAll() method returns a collection of Product objects. This collec- tion is retrieved from the SqlDataAccessLayer component. The Insert(), Update(), and Delete() methods validate their parameters before passing the parameters to the Data Access layer. For example, when you call the Insert() method, the length of the Name parameter is checked to verify that it is less than 50 characters. The Business Logic layer does not contain any data access logic. All this logic is contained in the Data Access layer. Creating the Data Access Layer The Data Access layer contains all the specialized code for interacting with a database. The Data Access layer consists of the single component in Listing 17.28. (A real-world applica- tion might contain dozens or even hundreds of components in its Data Access layer.) LISTING 17.28 DAL\SqlDataAccessLayer.cs using System; using System.Data; using System.Data.SqlClient; using System.Web.Configuration; From the Library of Wow! eBook ptg 766 CHAPTER 17 Building Components using System.Collections.Generic; using AcmeStore.BusinessLogicLayer; namespace AcmeStore.DataAccessLayer { /// <summary> /// Data Access Layer for interacting with Microsoft /// SQL Server 2008 /// </summary> public class SqlDataAccessLayer { private static readonly string _connectionString = string.Empty; /// <summary> /// Selects all products from the database /// </summary> public List<Product> ProductSelectAll() { // Create Product collection List<Product> colProducts = new List<Product>(); // Create connection SqlConnection con = new SqlConnection(_connectionString); // Create command SqlCommand cmd = new SqlCommand(); cmd.Connection = con; cmd.CommandText = “SELECT Id,Name,Price,Description FROM Products”; // Execute command using (con) { con.Open(); SqlDataReader reader = cmd.ExecuteReader(); while (reader.Read()) { colProducts.Add(new Product( (int)reader[“Id”], (string)reader[“Name”], (decimal)reader[“Price”], (string)reader[“Description”])); } } return colProducts; } From the Library of Wow! eBook ptg 767 Architectural Considerations 17 /// <summary> /// Inserts a new product into the database /// </summary> /// <param name=”newProduct”>Product</param> public void ProductInsert(Product newProduct) { // Create connection SqlConnection con = new SqlConnection(_connectionString); // Create command SqlCommand cmd = new SqlCommand(); cmd.Connection = con; cmd.CommandText = “INSERT Products (Name,Price,Description) VALUES (@Name,@Price, // Add parameters cmd.Parameters.AddWithValue(“@Name”, newProduct.Name); cmd.Parameters.AddWithValue(“@Price”, newProduct.Price); cmd.Parameters.AddWithValue(“@Description”, newProduct.Description); // Execute command using (con) { con.Open(); cmd.ExecuteNonQuery(); } } /// <summary> /// Updates an existing product into the database /// </summary> /// <param name=”productToUpdate”>Product</param> public void ProductUpdate(Product productToUpdate) { // Create connection SqlConnection con = new SqlConnection(_connectionString); // Create command SqlCommand cmd = new SqlCommand(); cmd.Connection = con; cmd.CommandText = “UPDATE Products SET Name=@Name,Price=@Price,Description= // Add parameters cmd.Parameters.AddWithValue(“@Name”, productToUpdate.Name); cmd.Parameters.AddWithValue(“@Price”, productToUpdate.Price); From the Library of Wow! eBook ptg 768 CHAPTER 17 Building Components cmd.Parameters.AddWithValue(“@Description”, productToUpdate.Description); cmd.Parameters.AddWithValue(“@Id”, productToUpdate.Id); // Execute command using (con) { con.Open(); cmd.ExecuteNonQuery(); } } /// <summary> /// Deletes an existing product in the database /// </summary> /// <param name=”id”>Product Id</param> public void ProductDelete(int Id) { // Create connection SqlConnection con = new SqlConnection(_connectionString); // Create command SqlCommand cmd = new SqlCommand(); cmd.Connection = con; cmd.CommandText = “DELETE Products WHERE Id=@Id”; // Add parameters cmd.Parameters.AddWithValue(“@Id”, Id); // Execute command using (con) { con.Open(); cmd.ExecuteNonQuery(); } } /// <summary> /// Initialize the data access layer by /// loading the database connection string from /// the Web.Config file /// </summary> static SqlDataAccessLayer() { From the Library of Wow! eBook ptg 769 Summary 17 _connectionString = WebConfigurationManager.ConnectionStrings[“Store”].ConnectionString; if (string.IsNullOrEmpty(_connectionString)) throw new Exception(“No connection string configured in Web.Config file”); } } } The SqlDataAccessLayer component in Listing 17.28 grabs the database connection string that it uses when communicating with Microsoft SQL Server in its constructor. The connection string is assigned to a private field so that it can be used by all the compo- nent’s methods. The SqlDataAccessLayer component has four public methods: ProductSelectAll(), ProductInsert(), ProductUpdate(), and ProductDelete(). These methods use the ADO.NET classes from the System.Data.SqlClient namespace to communicate with Microsoft SQL Server. NOTE We discuss ADO.NET in Chapter 19, “Building Data Access Components with ADO.NET.” NOTE In this section, the Data Access layer was built using ADO.NET. It could just have as easily been built using LINQ to SQL. We discuss LINQ to SQL in Chapter 20. The SqlDataAccessLayer component is not completely isolated from the components in the Business Logic layer. The ProductSelectAll() method builds a collection of Product objects, which the method returns to the Business Logic layer. You should strive to isolate each layer as much as possible. However, in some cases, you cannot completely avoid mixing objects from different layers. Summary In this chapter, you learned how to build components in .NET Framework. In the first part, you were given an overview of component building. You learned how to take advan- tage of dynamic compilation by using the App_Code folder. You also learned how to create component properties, methods, and constructors. You also examined several advanced topics related to components such as overloading, inheritance, MustInherit classes, and interfaces. From the Library of Wow! eBook ptg 770 In the second half of this chapter, you learned how to build component libraries. You saw different methods for compiling a set of components into an assembly. You also examined how you can add components to both an application’s Bin folder and the Global Assembly Cache. Finally, you had a chance to consider architectural issues related to building applications with components. You learned how to build a three-tiered application, divided into isolated User Interface, Business Logic, and Data Access layers. CHAPTER 17 Building Components From the Library of Wow! eBook ptg CHAPTER 18 Using the ObjectDataSource Control IN THIS CHAPTER . Representing Objects with the ObjectDataSource Control . Using Parameters with the ObjectDataSource Control . Paging, Sorting, and Filtering Data with the ObjectDataSource Control . Handling ObjectDataSource Control Events . Concurrency and the ObjectDataSource Control . Extending the ObjectDataSource Control . Summary The ObjectDataSource control enables you to bind DataBound controls such as the GridView, DetailsView, and FormView controls to a component. You can use the ObjectDataSource control to easily build multitier applica- tions with ASP.NET Framework. Unlike the SqlDataSource control, which mixes data access logic in the User Interface layer, the ObjectDataSource control enables you to cleanly separate your User Interface layer from your Business Logic and Data Access layers. In this chapter, you learn how to use the ObjectDataSource control to represent different types of objects. For example, you learn how to use the ObjectDataSource control with components that represent database data. You also learn how to use the ObjectDataSource control to represent different types of method parameters. We tackle a number of advanced topics. For example, you learn how to page, sort, and filter database records repre- sented by the ObjectDataSource control. You learn how to page and sort through large database tables efficiently. In the final section, you learn how to extend the ObjectDataSource control to represent specialized data sources. You also learn how to extend the ObjectDataSource control with custom parameters. From the Library of Wow! eBook ptg 772 CHAPTER 18 Using the ObjectDataSource Control Representing Objects with the ObjectDataSource Control The ObjectDataSource control includes five main properties: . TypeName—The name of the type of object that the ObjectDataSource control represents. . SelectMethod—The name of a method that the ObjectDataSource calls when selecting data. . UpdateMethod—The name of a method that the ObjectDataSource calls when updating data. . InsertMethod—The name of a method that the ObjectDataSource calls when inserting data. . DeleteMethod—The name of a method that the ObjectDataSource calls when deleting data. An ObjectDataSource control can represent any type of object in .NET Framework. This section discusses several types of objects you might want to represent. For example, you learn how to use the ObjectDataSource control with components that represent collec- tions, ADO.NET DataReaders, DataSets, LINQ to SQL queries, and web services. NOTE You can use the ObjectDataSource control to represent any object (any class that derives from the System.Object class). If the object does not support the IEnumerable interface, the ObjectDataSource control automatically wraps the object in a new object that supports the IEnumerable interface. You can even represent an ASP.NET ListBox control with an ObjectDataSource (not that a ListBox has any inter- esting methods). Binding to a Component Let’s start with a simple component. The component in Listing 18.1 is named MovieCollection and contains one method named GetMovies(), which returns a collection of movie titles. LISTING 18.1 MovieCollection.cs using System; using System.Web.Configuration; using System.Collections.Generic; public class MovieCollection From the Library of Wow! eBook ptg 773 Representing Objects with the ObjectDataSource Control { public List<string> GetMovies() { List<string> movies = new List<string>(); movies.Add(“Star Wars”); movies.Add(“Independence Day”); movies.Add(“War of the Worlds”); return movies; } } You can use the page in Listing 18.2 to display the list of movies returned by the GetMovies() method in a GridView control. The page contains an ObjectDataSource control that represents the MovieCollection component. LISTING 18.2 ShowMovieCollection.aspx <%@ Page Language=”C#” %> <!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.1//EN” “http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd”> <html xmlns=”http://www.w3.org/1999/xhtml” > <head id=”Head1” runat=”server”> <title>Show Movie Collection</title> </head> <body> <form id=”form1” runat=”server”> <div> <asp:GridView id=”grdMovies” DataSourceID=”srcMovies” Runat=”server” /> <asp:ObjectDataSource id=”srcMovies” TypeName=”MovieCollection” SelectMethod=”GetMovies” Runat=”server” /> </div> </form> </body> </html> 18 From the Library of Wow! eBook . <param name=”name”>Product Name</param> /// <param name=”price”>Product Price</param> /// <param name=”description”>Product Description</param> public Product(int. /// <param name=”price”>Product Price</param> /// <param name=”description”>Product Description</param> public Product(string name, decimal price, string description) . = “UPDATE Products SET Name=@Name,Price=@Price,Description= // Add parameters cmd.Parameters.AddWithValue(“@Name”, productToUpdate.Name); cmd.Parameters.AddWithValue(“@Price”, productToUpdate.Price);