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Developing a Shopping Cart - Part 3

王朝asp·作者佚名  2006-01-31
窄屏简体版  字體: |||超大  

source:

http://www.dotnetbips.com/displayarticle.aspx?id=286

begin:

Download Source Code

Developing a Shopping Cart - Part 3

Introduction

In the previous article we saw how to create a shopping cart using

session variables.

Continuing the concept further this article will illustrate how to use store

your shopping cart in a database. This technique is more robust and scalable

that the previous two techniques.

Creating a database table

Before you proceed with any coding, you need to create the following table in

the Northwind database of SQL Server.

CREATE TABLE [dbo].[ShoppingCart_Products] (

[ID] [int] IDENTITY (1, 1) NOT NULL ,

[CartID] [varchar] (50),

[ProductID] [int] NULL,

[ProductName] [varchar] (255),

[UnitPrice] [money] NULL ,

[Quantity] [int] NULL

) ON [PRIMARY]

Developing a simple product listing page

We will first build a simple web form that lists Products table of Northwind

database in a DataGrid.

Create a new web project in VS.NET with C# as the language.Add a web form called ProductCatalog.aspx to itDrag and drop a DataGrid control on it.Write a function called BindGrid() as shown below:

private void BindGrid()

{

SqlDataAdapter da=

new SqlDataAdapter

("select * from products",

@"data source=.\vsdotnet;initial catalog=northwind;user id=sa");

DataSet ds=new DataSet();

da.Fill(ds,"products");

DataGrid1.DataSource=ds;

DataGrid1.DataBind();

}

Call this function in the Page_Load event handler

private void Page_Load(object sender, System.EventArgs e)

{

if(!Page.IsPostBack)

{

BindGrid();

}

}

Write following code in the SelectedIndexChanged event of the

DataGrid.

private void DataGrid1_SelectedIndexChanged

(object sender, System.EventArgs e)

{

CShoppingCartItem item=new CShoppingCartItem();

item.ProductID=

int.Parse(DataGrid1.SelectedItem.Cells[1].Text);

item.ProductName=

DataGrid1.SelectedItem.Cells[2].Text;

item.UnitPrice=

decimal.Parse(DataGrid1.SelectedItem.Cells[3].Text);

item.Quantity=1;

CShoppingCart.AddItem(Session.SessionID,item);

}

Here, create an instance of CSHoppingCartItem class and set its properties.

We then call AddMethod of CShoppingCart class. Both of these classes are

explained in the following text.

Drag and drop a button control on the web form and write

following code in the it's click event handler.

private void Button1_Click

(object sender, System.EventArgs e)

{

Response.Redirect("cart.aspx");

}

Here, we are simply navigating to the cart.aspx page which displays the

shopping cart.

The CShoppingCartItem class

This class represents a single item of the shopping cart and looks as shown

below:

public class CShoppingCartItem

{

private int intProductID;

private string strProductName;

private decimal decUnitPrice;

private int intQuantity;

public int ProductID

{

get

{

return intProductID;

}

set

{

intProductID=value;

}

}

public string ProductName

{

get

{

return strProductName;

}

set

{

strProductName=value;

}

}

public decimal UnitPrice

{

get

{

return decUnitPrice;

}

set

{

decUnitPrice=value;

}

}

public int Quantity

{

get

{

return intQuantity;

}

set

{

intQuantity=value;

}

}

}

The CShoppingCart class

This is the most important class in our application because it actually

performs the job of storing or retrieving shopping cart items into a database

table. It consists of static methods and looks as shown below:

public class CShoppingCart

{

private static string connstr=

@"data source=.\vsdotnet;initial

catalog=northwind;user id=sa";

public static

void AddItem(string cartid,CShoppingCartItem item)

{

SqlConnection cnn=new SqlConnection(connstr);

SqlCommand cmd=new SqlCommand();

cmd.Connection=cnn;

cmd.CommandText=

"insert into ShoppingCart_Products(cartid,productid,

productname,unitprice,quantity)

values(@cartid,@prodid,@prodname,@unitprice,@qty)";

SqlParameter p1=new SqlParameter("@cartid",cartid);

SqlParameter p2=new

SqlParameter("@prodid",item.ProductID);

SqlParameter p3=new

SqlParameter("@prodname",item.ProductName);

SqlParameter p4=new

SqlParameter("@unitprice",item.UnitPrice);

SqlParameter p5=new

SqlParameter("@qty",item.Quantity);

cmd.Parameters.Add(p1);

cmd.Parameters.Add(p2);

cmd.Parameters.Add(p3);

cmd.Parameters.Add(p4);

cmd.Parameters.Add(p5);

cnn.Open();

cmd.ExecuteNonQuery();

cnn.Close();

}

public static

void UpdateQuantity

(string cartid,int productid,int newqty)

{

SqlConnection cnn=new SqlConnection(connstr);

SqlCommand cmd=new SqlCommand();

cmd.Connection=cnn;

cmd.CommandText=

"update ShoppingCart_Products

set quantity=@qty where cartid=@cartid

and productid=@prodid";

SqlParameter p1=new SqlParameter("@qty",newqty);

SqlParameter p2=new SqlParameter("@cartid",cartid);

SqlParameter p3=new SqlParameter("@prodid",productid);

cmd.Parameters.Add(p1);

cmd.Parameters.Add(p2);

cmd.Parameters.Add(p3);

cnn.Open();

cmd.ExecuteNonQuery();

cnn.Close();

}

public static void DeleteItem(string cartid,int productid)

{

SqlConnection cnn=new SqlConnection(connstr);

SqlCommand cmd=new SqlCommand();

cmd.Connection=cnn;

cmd.CommandText=

"delete from ShoppingCart_Products

where cartid=@cartid and productid=@prodid";

SqlParameter p1=new SqlParameter("@cartid",cartid);

SqlParameter p2=new SqlParameter("@prodid",productid);

cmd.Parameters.Add(p1);

cmd.Parameters.Add(p2);

cnn.Open();

cmd.ExecuteNonQuery();

cnn.Close();

}

public static DataSet GetAll(string cartid)

{

SqlDataAdapter da=new SqlDataAdapter

("select * from ShoppingCart_Products

where cartid='" + cartid + "'",connstr);

DataSet ds=new DataSet();

da.Fill(ds,"shoppingcart");

return ds;

}

}

This class uses SqlConnection, SqlCommand and SqlDataReader classes to

perform various tasks such as INSERT, UPDATE and SELECT.

Creating the shopping cart web form

Add another web form to the above project called cart.aspxDrag and drop a DataGrid on the web form.Create a function called FillCartFromDb() as shown below:

private void FillCartFromDb()

{

DataSet ds=CShoppingCart.GetAll(Session.SessionID);

DataGrid1.DataSource=ds;

DataGrid1.DataBind();

Button1_Click(null,null);

}

Here, we call the GetAll method of the CShoppingCart class which returns a

DataSet. This DataSet acts as a datasource for the DataGrid control.

Drag and drop a button called Recalculate and write following

code to its click event handler

private void Button1_Click

(object sender, System.EventArgs e)

{

decimal total=0;

try

{

foreach(DataGridItem dgi in DataGrid1.Items)

{

if(dgi.ItemType==ListItemType.Item

|| dgi.ItemType==ListItemType.AlternatingItem)

{

TextBox t=(TextBox)dgi.Cells[3].Controls[1];

int quantity=int.Parse(t.Text);

decimal unitprice=Decimal.Parse(dgi.Cells[2].Text);

total=total + (unitprice * quantity);

CShoppingCart.UpdateQuantity

(Session.SessionID,int.Parse(dgi.Cells[0].Text),quantity);

}

}

}

catch

{

}

lblAmt.Text=total.ToString();

}

This code calculates the total amount of the items selected based on the

quantity entered and displays it in a label.

Finally, we will write code to delete items from the cart.

private void DataGrid1_DeleteCommand

(object source,

System.Web.UI.WebControls.DataGridCommandEventArgs e)

{

CShoppingCart.DeleteItem

(Session.SessionID,int.Parse(e.Item.Cells[0].Text));

FillCartFromDb();

}

Here, we simply simply delete a particular product by calling the DeleteItem

method of CShoppingCart class.

Code Download

The complete working example is available for download. Please see the link

at the top of the article.

Summary

In this article we saw how to use SQL Server database to store a shopping

cart. This approach though requires more coding is recommended for big

sites. Since you are storing the data in a SQL server database, you are not

putting any overhead on the web server (as against Session variables). Also,

this approach is better than cookies because you are not dependent of client

browser supporting cookies. In terms of performance this approach will however

be slower than the other two techniques. However, overall it is more robust and

scalable than cookies or sessions. In the next article I will illustrate how to

create a single wrapper to all he three approaches so that without any code

change you can switch between these three techniques.

About the author

Name :

Bipin Joshi

Email :

webmaster at dotnetbips.com

Profile :

Bipin

Joshi is the webmaster of DotNetBips.com. He is the founder of

BinaryIntellect Consulting (www.binaryintellect.com) - a company

providing training and consulting services on .NET framework. He

conducts intensive training programs in Thane/Mumbai for developers. He

is also a Microsoft MVP (ASP.NET) and a member of ASPInsiders.

 
 
 
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