ASP.NET 4 Unleased - p 80 pdf

newProduct.Save; } /// /// Deletes an existing product /// /// Product Id public static void Deleteint id { if id < 1 throw new ArgumentException“Product Id must be greater than 0”, ➥“

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)

: 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;

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;

}

/// <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);

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()

{

_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

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

Using the ObjectDataSource

Control

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

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

{

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>