C# shopping basket, trying to remove an item...

Righty then

Create a new class in the folder entities in Common

Call it CartItem and make it public (similar to the Player or News classes)

Build it up to match your database entity (row)

Add a new Class in the DataAccess project and class it CartItemDal.cs

Make the class public

Create a method called public void Save(CartItem obj)

In the Save method

Make it up similar to this one

public void Save(CartItem obj)
        {
            SqlParameter[] sqlParameters = {
                                               DbHelper.MakeInParam("ParamName1",SqlDbType.VarChar,250,obj.ParamName1),
                                               DbHelper.MakeInParam("ParamName2",SqlDbType.VarChar,5000,obj.ParamName2)
                                           };
            var dbHelper = new DbHelper();
            dbHelper.RunProc<int>("usp_insert_CartItem", sqlParameters);
            dbHelper.Dispose();
        }

Replace the ParamName1 and 2 with your items and add more if you need them. Also change the SqlDbTypes and lengths to match what you need

Now in the Business project,

Add a new class to the project and call it CartItemBl.cs

Make the class public

Create a new static method call Save(params....)

Eg

 public static void Save(string P1,string P2)
        {
            var CartItem= new CartItem {Param1= P1, Param2 = P2};
            var CartItemDal = new CartItemDal();
            CartItemDal.Save(news);
        }

Now in your aspx file, on your say button click event to save

var P1= P1.Text;
            var P2 = P2.Content;
            CartItemBl.Save(P1,P2);

You will need to add the using statements as you go along (or if you are using VS2008 do ctrl + . to shortcut it)

So in order

CartItemDal (using Common.Entities)
CartItemBl (using Common.Entities & DataAccess)
ASPX file (using Business)

And finally you need to create the stored proc to save the stuff but that ok?

Jobs done

Oki doki

I created a shopping cart demo for you.

Consists of 2 pages. Catalog and ShoppingCart

Catalog displays all the products and allows you to add them to your cart.

ShoppingCart shows the contents of your cart and alls you to remove them from the cart.

Its extremely basic, I wrote it in about 2 hours over brekkie so there is feck all error handling in it ie none.

Targetted for .NET 2.0 and built using VS 2008. You can import the projects one by one into VS2005.

Just create a blank solution and and the projects in the following order

Common
DataAccess
Business
ShoppingCartDemo (ASPX Site)

You will possibly need to readd the references

DataAccess references Common
Business references Common and DataAccess
ShoppingCartDemo references Business and Common

Code is commented somewhat to make it easier to understand.

DB Script to recreate the database and procs included. Add some data.

Now you will need to adjust your connection string.

HTH

You call the database whatever you like, just change the name in the the connection string

In the web.config you will see

<connectionStrings>
<add name="default" connectionString="Data Source=localhost;Initial Catalog=ShoppingCartDemo;User Id=ShoppingCartDemoUser;Password=password;"/>
</connectionStrings>

Change the Data Source to the name or IP of the server or whatever the hosting company says it should be

Change Initial Catalog to the name of your database

Change the User Id to the name of your user that will have access to the database and similarly the password

Righty then

I will go through the Catalog.aspx file for you and show it all works

Firstly you need to look at the project called common. It contains 2 classes. Product and CartItem

    public class Product
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Description { get; set; }
        public int Cost { get; set; }
    }

   public class CartItem : Product
    {
        public int Amount { get; set; }
    }

The product class represents strangely enough the product with a Name, Description and Cost etc. CartItem inherits (gets the same) these properties from Product and add its own property called Amount. This allows us to have a number of the same products in the cart and just to hold an amount value for them.

These classes are common to all the projects in the solution (hence the project name common).

Now in Catalog.aspx, it has just a couple of things on it. One is a repeater which shows the data the way I want it.

So if you look at the repeater in the source code of the aspx fille you see

<asp:Repeater ID="_Catalog" runat="server">
    <HeaderTemplate>
    <table>
    <tr>
    <td>Name</td>
    <td>Description</td>
    <td>Cost</td>
    <td>&nbsp;</td>
    </tr>
    </HeaderTemplate>
    <ItemTemplate>
    <tr>
    <td><%# ((Product)Container.DataItem).Name %></td>
    <td><%# ((Product)Container.DataItem).Description %></td>
    <td><%# ((Product)Container.DataItem).Cost.ToString(CultureInfo.InvariantCulture) %></td>
    <td><asp:Button ID="_AddToCart" CommandArgument="<%# ((Product)Container.DataItem).Id.ToString() %>" CommandName="AddToCart" runat="server" Text="Buy this" /> </td>
    </tr>
    </ItemTemplate>
    <FooterTemplate>
    </FooterTemplate>
    </asp:Repeater>

What a repeater does, is it takes a datasource, in our case a list of products and outputs them in the way that we define it in the <ItemTemplate> part of the repeater.

You will see that I have a HTML table row (tr) and a couple of cells in which I put the different values using the Container.DataItem function... except I tell to make it into a Product class so I can access the properties easier

<%# ((Product)Container.DataItem).Name %>

Now the final trick is the button.

<asp:Button ID="_AddToCart" CommandArgument="<%# ((Product)Container.DataItem).Id.ToString() %>" CommandName="AddToCart" runat="server" Text="Buy this" />

What this does is the following. I tell it to send the Id of the product back using the CommandArgument part of the code and I tell it that I want the command it sends back to be AddToCart. I could change this to any value I want.

So every product in the list outputs a Name, Description and Cost and a button with its Id as the command argument in a seperate table row.

Now into the code behind of Catalog.aspx

The first thing that happens when you enter the page is that I assign a handler to catch the events from the repeater.

protected override void OnInit(EventArgs e)
        {
            //Add an event handler to handle our button events in the repeater
            _Catalog.ItemCommand += CatalogItemCommand;

            base.OnInit(e);
        }

This catches when the button is clicked.

Next thing is that the Page_Load event fires.

      protected void Page_Load(object sender, EventArgs e)
        {
            //Only bind the first time
            if (Page.IsPostBack) return;
            _Catalog.DataSource = ProductBl.GetAllProducts();
            _Catalog.DataBind();

            _CartSize.Text = Session["Cart"] != null ? ((List<CartItem>) Session["Cart"]).Count.ToString() : "0";
        }

I check to see if the page is a postback because I dont want to rebind the data everytime, only the first time.

My DataSource for the repeater is a function in the ProductBL (Business Layer). It returns a generic list of products.

public static List<Product> GetAllProducts()
        {
            ProductDal productDal = new ProductDal();
            return productDal.GetAllProducts();
        }

The function GetAllProducts in the ProductBl is basically a pass through to the DataAccess project. Because I have minimal business logic in this solution I dont really need a Business layer but I put it in just to show how its done.

The GetAllProducts function in the DataAccess project (ProductDal.cs) does the following.

public List<Product> GetAllProducts()
        {
            DbHelper dbHelper = new DbHelper();

            DataSet dataSet = dbHelper.RunProcDs("usp_select_allProducts");

            return Common.CreateList<Product>(dataSet);
        }

Firstly it creates a DbHelper object which manages all my connections and interactions with the database. By using something like this helper object I dont need to do all the same open db stuff every time.

I create a dataset and tell it that its to be filled from the RunProcDs command in the helper. I tell it run the stored procedure usp_select_allProducts.

This stored proc is simply the following SQL

SELECT Id,[Name],Description,Cost FROM Product

I then use another one of my helper classes. This one takes a dataset and creates a list of objects from that data. This function is located in Common.cs file.

It does this using a trick called Reflection. In .NET you can find out all the property names of an object. So get all the names of the properties of the object I want to create, in this case Product, which is Id,Name,Description and Cost. See the names of the properties in the class are the same as the names of the columns in the database.

So I tell it to loop through all the properties in the class and put the value of the column with the same name into the property. Eg

Product.Id = datarow["Id"]

And because the data type of the property and the one in the database are the same it works happily.

        internal static T CreateObject<T>(DataRow row) where T : new()
        {
            PropertyInfo[] propertyInfos = typeof (T).GetProperties();

            T obj = new T();

            foreach (var info in propertyInfos)
            {
                info.SetValue(obj, row[info.Name], null);
            }

            return obj;
        }

        internal static List<T> CreateList<T>(DataSet dataSet) where T : new()
        {
            List<T> list = new List<T>();

            foreach (DataRow dataRow in dataSet.Tables[0].Rows)
            {
                list.Add(CreateObject<T>(dataRow));
            }

            return list;
        }

How do I tell it what object to create. Using a technique known as Generics, I can tell the program to expect some type of object and to work with that.

So in the function CreateObject for example, I tell it that it will be an object of type T (ie I dont know), and that I will let it know at runtime.

The reason for using Generics means I dont need to create a function for each object, which if you are using a lot of objects that would be a lot of repeated code.

At this stage the DataAccess project has a list of products and returns that to the Business project which in turn returns it to Catalog.aspx. This looks like a long trip but because everything is designed to just get the job done its very quick.

The repeater binds to this list and the stuff in ItemTemplate tells it how to show it.

With me so far??

Right then, on to the all important button that adds stuff to the cart.

When you click the button, the page does a postback, and because I have an event handler to handle anything that happens in the repeater, it goes in there. (It doesnt rebind because we check for that)

So the code for the function is

private void CatalogItemCommand(object source, RepeaterCommandEventArgs e)
        {
            if (!Equals(e.CommandName, "AddToCart")) return;

            //Check if the session is null and assign the correct list
            List<CartItem> cartItems = Session["Cart"] != null ? (List<CartItem>) Session["Cart"] : new List<CartItem>();

            //Get the item I want from the database.
            CartItem cartItem = ProductBl.GetItem<CartItem>(Convert.ToInt32(e.CommandArgument));

            // This section can be used if you wanted to see if there was an item matching.
            CartItem hasitem = cartItems.Find((delegate(CartItem ci) { return ci.Id == cartItem.Id; }));

            //If the item exists, get its current amount and add 1. Then remove it
            if (hasitem != null)
            {
                cartItem.Amount = hasitem.Amount + 1;
                cartItems.Remove(hasitem);
            }
            else
            {
                cartItem.Amount = 1;
            }

            //add our item to the cart with its correct amount
            cartItems.Add(cartItem);

            //put the cart back into the session state
            Session["Cart"] = cartItems;

            //This displays the size of the list which is the number of items but not the quantity
            _CartSize.Text = cartItems.Count.ToString();
        }

What I do first is check what type of command I am getting, ie AddToCart. If you have a couple of different buttons or linkbuttons or whatever you could use that check to find what code to run.

List<CartItem> cartItems = Session["Cart"] != null ? (List<CartItem>) Session["Cart"] : new List<CartItem>();

Now the next line creates a new list of cartitem and assigns the value either to a new list or the list in my session. The syntax that it uses is just shorthand.

So now I have a list of cartitem.

CartItem cartItem = ProductBl.GetItem<CartItem>(Convert.ToInt32(e.CommandArgument));

I create a new cartitem by using the function caaled GetItem and pass in the id of the product I want. This Id is the CommandArgument that i set in my button. The getting the details works the exact same as getting the list as described above.

Now the next bit is a bit funky.

I want to see if the person already put the same product in the cart and if they did, I want to increase the quantity by 1.

So I create a new cartitem and try to find it in my list. If its there, it will come back as the same object otherwise it will be null.

So I check to see if my hasitem is null and if its not, I add 1 to the amount and then I remove it from my list so that I only add the object once. You will see why in a minute.

If the hasitem is null, I just use my new cartitem above and set amount to 1.

After all that, I have a cartitem that has the correct amount and add that to the list.

I then put the list back into the session (or for the first time it doesnt matter) and then I set the label to the count size of the list, which isnt the actual number of items but just the number of items in the list eg if you have 2 products with amounts of 2, it wont show 4, it will only show that you have 2 items because its using the count on the list.

So that is the catalog page explained.

I will do ShoppingCart in the next post!

Button 1 is the purchase button isnt it

Ok the way that I would do this, is the following

You will notice there are 2 repeaters on the new Catalog.aspx page.

I am going to be very blunt and tell you to use a repeater and scrap your previous methods as its not good, confusing the crap out of you and its easier to see what is happening with this code (a lot less spaghetti!) I dont normally tell people to do this

Where you normally outputted your car part and session info, remove it. Remove your purchase button as well, basically I want all the stuff including what is in the DropdownList3 SelectedIndex changed removed. Keep Ddl1 and 2 as is they are ok for the moment.

Use the repeater sample I gave you and edit the item template to output the information how you want.

In the database create a new stored procedure that gets back the list of products eg From your code

SELECT * FROM Vehicle_Data WHERE Vehicle_Make = '" + DropDownList1.SelectedItem.Value + "' AND Vehicle_Model = '" + DropDownList2.SelectedItem.Value + "' AND Engine_Type = '" + DropDownList3.SelectedItem.Value + "'

CREATE PROCEDURE dbo.usp_select_product
(
@Make VARCHAR(200),
@Model VARCHAR(200),
@Engine VARCHAR(200)
)
SELECT etc etc

Now create a method in DataAccess that takes 3 string params and executes that proc and returns a list of information (similar to GetAllProducts is written)

In Business create a method that takes 3 string params and returns a List<Product>, same as GetAllProducts

Finally in your SelectedIndexChanged in DropDownList3 (assuming the repeater is called _Catalog)

_Catalog.DataSource = Business.YourMethodName(string1,string2,string3);
_Catalog.DataBind();

This will output the data in the way you want, and give you a purchase button for each item.

Now you can use the exact same code as in Catalog.aspx to put the items in the cart and show them in the Cart repeater.

What I am trying to do here is simplify the whole process for you, so you can just databind and forget

I am working on the idea that you are using the solution I provided as a base at this point.. If you are'nt it would be handy to know...

Ok

Might I suggest something

Go slowly

Dont bring in old code in such a large chuck, it just adds to the problem..

WHat you should do is create the dropdowns again and get them working so that they bring back the correct cascade sequence.

Then start looking at binding the correct data to the repeater.

Once you have done that you can skin the page and its nearly finished for you