ASP.NET 4 Unleased - p 46 pps

CHAPTER 9 Using the SqlDataSource Control The current movie category is added to the Session object in the Page_Load method.. Programmatically Executing SqlDataSource Commands You a

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CHAPTER 9 Using the SqlDataSource Control

<asp:DetailsView

id=”dtlMovie”

DataSourceID=”srcMovie”

Runat=”server” />

<asp:HyperLink

Runat=”server”

Text=”Back ”

NavigateUrl=”~/ShowQueryStringParameterMaster.aspx” />

<asp:SqlDataSource

id=”srcMovie”

SelectCommand=”SELECT * FROM Movies

WHERE Id=@Id”

ConnectionString=”<%$ ConnectionStrings:Movies %>”

Runat=”server”>

<asp:QueryStringParameter

Name=”Id”

QueryStringField=”Id” />

</SelectParameters>

</asp:SqlDataSource>

</div>

</form>

</body>

</html>

The SqlDataSource control in Listing 9.24 includes a QueryStringParameter The

QueryStringParameter supplies the movie ID in the SqlDataSource control’s

SelectCommand

Using the SessionParameter Object

The SessionParameter object enables you to represent any item stored in Session state

The SessionParameter object includes all the properties of the base Parameter class and

the following property:

SessionField—The name of the item stored in Session state that the

SessionParameter represents

NOTE

Session state is discussed in detail in Chapter 28

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The page in Listing 9.25 contains a GridView that displays a list of movies matching a

movie category The movie category is stored in Session state

LISTING 9.25 ShowSessionParameter.aspx

<%@ Page Language=”C#” %>

<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.1//EN”

“http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd”>

void Page_Load()

{

Session[“MovieCategoryName”] = “Animation”;

}

</script>

<title>Show SessionParameter</title>

</head>

<body>

<div>

<asp:GridView

id=”grdMovies”

DataSourceID=”srcMovies”

<asp:SqlDataSource

id=”srcMovies”

SelectCommand=”SELECT Name As Category,Title,Director

FROM Movies

INNER JOIN MovieCategories

ON CategoryId = MovieCategories.id

WHERE Name=@Name”

ConnectionString=”<%$ ConnectionStrings:Movies %>”

Runat=”server”>

<asp:SessionParameter

Name=”Name”

SessionField=”MovieCategoryName” />

</SelectParameters>

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</div>

</form>

</body>

</html>

The current movie category is added to the Session object in the Page_Load() method

The SqlDataSource reads the MovieCategoryName item from Session state when it

retrieves the list of movies that the GridView displays

Programmatically Executing SqlDataSource

Commands

You aren’t required to use the SqlDataSource control only when working with DataBound

controls You can create parameters and execute the commands represented by a

SqlDataSource control by working directly with the properties and methods of the

SqlDataSource control in your code

In this section, you learn how to add parameters programmatically to a SqlDataSource

control You also learn how to execute select, insert, update, and delete commands when

using the SqlDataSource control

Adding ADO.NET Parameters

Under the covers, the SqlDataSource control uses ADO.NET objects such as the ADO.NET

DataSet, DataReader, Parameter, and Command objects to interact with a database In

particular, any ASP.NET Parameter objects that you declare when working with the

SqlDataSource control get converted into ADO.NET Parameter objects

In some cases, you want to work directly with these ADO.NET Parameter objects when

using the SqlDataSource control For example, you might want to add additional

ADO.NET parameters programmatically before executing a command

The page in Listing 9.26 automatically adds an ADO.NET Parameter that represents the

current user’s username to the command that the SqlDataSource executes

LISTING 9.26 AddParameter.aspx

<%@ Import Namespace=”System.Data.SqlClient” %>

protected void srcGuestBook_Inserting(object sender,

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{

e.Command.Parameters.Add(new SqlParameter(“@Name”, User.Identity.Name));

}

</script>

<title>Show ProfileParameter</title>

</head>

<body>

<div>

<asp:FormView

id=”frmGuestBook”

DataSourceID=”srcGuestBook”

DefaultMode=”Insert”

Runat=”server”>

<asp:Label

id=”lblComments”

Text=”Enter Your Comments:”

<br />

<asp:TextBox

id=”txtComments”

Text=’<%# Bind(“Comments”) %>’

TextMode=”MultiLine”

Columns=”50”

Rows=”4”

<br />

<asp:Button

id=”btnInsert”

Text=”Add Comments”

CommandName=”Insert”

</InsertItemTemplate>

</asp:FormView>

<hr />

<asp:GridView

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id=”grdGuestBook”

DataSourceID=”srcGuestBook”

<asp:SqlDataSource

id=”srcGuestBook”

SelectCommand=”SELECT Name,Comments,EntryDate

FROM GuestBook ORDER BY Id DESC”

InsertCommand=”INSERT GuestBook (Name,Comments)

VALUES (@Name,@Comments)”

ConnectionString=”<%$ ConnectionStrings:GuestBook %>”

Runat=”server” OnInserting=”srcGuestBook_Inserting” />

</div>

</form>

</body>

</html>

The page in Listing 9.26 includes a srcGuestBook_Inserting() event handler, which

executes immediately before the SqlDataSource control executes its insert command In

the event handler, a new ADO.NET Parameter is added to the insert command, which

represents the current user’s username

NOTE

The names of ADO.NET parameters, unlike ASP.NET parameters, always start with the

character @

Executing Insert, Update, and Delete Commands

The SqlDataSource control has methods that correspond to each of the different types of

commands that it represents:

Delete—Enables you to execute a SQL delete command

Insert—Enables you to execute a SQL insert command

Select—Enables you to execute a SQL select command

Update—Enables you to execute a SQL update command

For example, the page in Listing 9.27 contains a form for adding new entries to the

GuestBook database table This form is not contained in a DataBound control such as the

FormView or DetailsView controls The form is contained in the body of the page When

you click the Add Entry button, the SqlDataSource control’s Insert() method is

executed

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LISTING 9.27 ExecuteInsert.aspx

/// <summary>

/// When button clicked, execute Insert command

/// </summary>

protected void btnAddEntry_Click(object sender, EventArgs e)

{

srcGuestBook.InsertParameters[“Name”].DefaultValue = txtName.Text;

srcGuestBook.InsertParameters[“Comments”].DefaultValue = txtComments.Text;

srcGuestBook.Insert();

}

</script>

<title>Execute Insert</title>

</head>

<body>

<div>

<asp:Label

id=”lblName”

Text=”Name:”

AssociatedControlId=”txtName”

<br />

<asp:TextBox

id=”txtName”

<asp:Label

id=”lblComments”

Text=”Comments:”

AssociatedControlId=”txtComments”

<br />

<asp:TextBox

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id=”txtComments”

Columns=”50”

Rows=”2”

<asp:Button

id=”btnAddEntry”

Text=”Add Entry”

Runat=”server” OnClick=”btnAddEntry_Click” />

<hr />

<asp:GridView

id=”grdGuestBook”

DataSourceId=”srcGuestBook”

<asp:SqlDataSource

id=”srcGuestBook”

ConnectionString=”<%$ ConnectionStrings:GuestBook %>”

SelectCommand=”SELECT Name,Comments FROM GuestBook

ORDER BY Id DESC”

InsertCommand=”INSERT GuestBook (Name,Comments)

VALUES (@Name,@Comments)”

Runat=”server”>

<asp:Parameter Name=”Name” />

<asp:Parameter Name=”Comments” />

</InsertParameters>

</div>

</form>

</body>

</html>

Executing Select Commands

The procedure for executing a select command is different from executing insert,

update, and delete commands because a select command returns data This section

discusses how you can execute the SqlDataSource control’s Select() method

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Remember that a SqlDataSource control can return either a DataView or DataReader

depending on the value of its DataSourceMode property The SqlDataSource control’s

Select() method returns an object of type IEnumerable Both DataViews and DataReaders

implement the IEnumerable interface

To understand how you can call the Select() method programmatically, look at the

following simple photo gallery application This application enables you to upload images

to a database table and display them in a page (see Figure 9.14)

FIGURE 9.14 A photo gallery application

First, you need to create the page that displays the images and contains the form for

adding new images The PhotoGallery.aspx page is contained in Listing 9.28

LISTING 9.28 PhotoGallery.aspx

<title>Photo Gallery</title>

</head>

<body>

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<div>

<asp:DataList

id=”dlstImages”

DataSourceID=”srcImages”

RepeatColumns=”3”

Runat=”server”>

<asp:Image ID=”Image1”

ImageUrl=’<%# String.Format(“DynamicImage.ashx?id={0}”, Eval(“Id”)) %>’

Width=”250”

<br />

<%# Eval(“Description”) %>

</ItemTemplate>

</asp:DataList>

<hr />

<asp:FormView

id=”frmImage”

DataSourceID=”srcImages”

DefaultMode=”Insert”

Runat=”server”>

<asp:Label

id=”lblImage”

Text=”Upload Image:”

AssociatedControlId=”upImage”

<br />

<asp:FileUpload

id=”upImage”

FileBytes=’<%# Bind(“Image”) %>’

<asp:Label

id=”lblDescription”

Text=”Description:”

AssociatedControlID=”txtDescription”

<br />

<asp:TextBox

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id=”txtDescription”

Text=’<%# Bind(“Description”) %>’

Columns=”50”

Rows=”2”

<asp:Button

id=”btnInsert”

Text=”Add Image”

CommandName=”Insert”

</InsertItemTemplate>

</asp:FormView>

<asp:SqlDataSource

id=”srcImages”

SelectCommand=”SELECT ID,Description FROM Images”

InsertCommand=”INSERT Images (Image,Description)

VALUES (@Image,@Description)”

ConnectionString=”<%$ ConnectionStrings:Images %>”

</div>

</form>

</body>

</html>

The page in Listing 9.28 has a FormView control that contains a FileUpload control You

can use the FileUpload control to upload images from your local hard drive to the

appli-cation’s database table

Also, the page contains a DataList control that displays the image The Image control

contained in the DataList control’s ItemTemplate points to a file named

DynamicImage.ashx, which represents an HTTP Handler that renders a particular image

The DynamicImage.ashx handler is contained in Listing 9.29

NOTE

HTTP handlers are discussed in detail in Chapter 31, “Working with the HTTP Runtime.”

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