ASP.NET 4 Unleased - p 44 ppt

ptg CHAPTER 9 Using the SqlDataSource Control LISTING 9.14 CancelCommand.aspx /// /// Iterate through all parameters and check for null /// protected void srcMovies_Updatingobject

Trang 1

ptg CHAPTER 9 Using the SqlDataSource Control

LISTING 9.14 CancelCommand.aspx

<%@ Page Language=”C#” %>

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

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

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

/// <summary>

/// Iterate through all parameters and check for null

/// </summary>

protected void srcMovies_Updating(object sender, SqlDataSourceCommandEventArgs e)

{

foreach (SqlParameter param in e.Command.Parameters)

if (param.Value == null)

{

e.Cancel = true;

lblError.Text = “All fields are required!”;

}

</script>

FIGURE 9.8 Canceling a command when a field is blank

Trang 2

.error

{

display:block;

color:red;

font:bold 16px Arial;

margin:10px;

}

td,th

{

padding:10px;

}

</style>

<title>Cancel Command</title>

</head>

<body>

<div>

<asp:Label

id=”lblError”

EnableViewState=”false”

CssClass=”error”

Runat=”server” />

<asp:DetailsView

id=”dtlMovie”

DataSourceID=”srcMovies”

DataKeyNames=”Id”

AllowPaging=”true”

AutoGenerateEditButton=”true”

<asp:SqlDataSource

id=”srcMovies”

SelectCommand=”SELECT * FROM Movies”

UpdateCommand=”UPDATE Movies SET Title=@Title,

Director=@Director,DateReleased=@DateReleased

WHERE Id=@id”

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

Runat=”server” OnUpdating=”srcMovies_Updating” />

</div>

</form>

</body>

</html>

Trang 3

CHAPTER 9 Using the SqlDataSource Control

The page in Listing 9.14 includes a srcMovies_Updating() method In this method, each

parameter associated with the update command is compared against the value Nothing

(null) If one of the parameters is null, an error message displays in a Label control

Using ASP.NET Parameters with the

SqlDataSource Control

You can use any of the following ASP.NET Parameter objects with the SqlDataSource

control:

Parameter—Represents an arbitrary static value

ControlParameter—Represents the value of a control or page property

CookieParameter—Represents the value of a browser cookie

FormParameter—Represents the value of an HTML form field

ProfileParameter—Represents the value of a Profile property

QueryStringParameter—Represents the value of a query string field

SessionParameter—Represents the value of an item stored in Session state

The SqlDataSource control includes five collections of ASP.NET parameters:

SelectParameters, InsertParameters, DeleteParameters, UpdateParameters, and

FilterParameters You can use these parameter collections to associate a particular

ASP.NET parameter with a particular SqlDataSource command or filter

In the following sections, you learn how to use each of these different types of parameter

objects

Using the ASP.NET Parameter Object

The ASP.NET parameter object has the following properties:

ConvertEmptyStringToNull—When true, if a parameter represents an empty string,

the empty string converts to the value Nothing (null) before the associated

command executes

DefaultValue—When a parameter has the value Nothing (null), the DefaultValue is

used for the value of the parameter

Direction—Indicates the direction of the parameter Possible values are Input,

InputOutput, Output, and ReturnValue

Name—Indicates the name of the parameter Do not use the @ character when

indi-cating the name of an ASP.NET parameter

Size—Indicates the data size of the parameter

Trang 4

Type—Indicates the NET Framework type of the parameter You can assign any value

from the TypeCode enumeration to this property

You can use the ASP.NET parameter object to indicate several parameter properties

explic-itly, such as a parameter’s type, size, and default value

For example, the page in Listing 9.15 contains a DetailsView control bound to a

SqlDataSource control You can use the page to update records in the Movies database

table (see Figure 9.9)

FIGURE 9.9 Updating movie records

LISTING 9.15 ShowDetailsView.aspx

<title>Show DetailsView</title>

</head>

<body>

<div>

<asp:DetailsView

Trang 5

id=”dtlMovie”

DefaultMode=”Edit”

runat=”server” />

<asp:SqlDataSource

id=”srcMovies”

SelectCommand=”Select * FROM Movies”

UpdateCommand=”UPDATE Movies SET Title=@Title,Director=@Director,

DateReleased=@DateReleased WHERE Id=@id”

</div>

</form>

</body>

</html>

In Listing 9.15, no ASP.NET parameter objects are declared explicitly The DetailsView

control automatically creates and adds ADO.NET parameters to the SqlDataSource

control’s update command before the command is executed

If you want to be explicit about the data types and sizes of the parameters used by a

SqlDataSource control, you can declare the parameters The page in Listing 9.16 declares

each of the parameters used when executing the update command

LISTING 9.16 ShowDetailsViewExplicit.aspx

<title>Show DetailsView Explicit</title>

</head>

<body>

<div>

Trang 6

<asp:DetailsView

id=”dtlMovie”

DefaultMode=”Edit”

runat=”server” />

<asp:SqlDataSource

id=”srcMovies”

SelectCommand=”Select * FROM Movies”

UpdateCommand=”UPDATE Movies SET Title=@Title,Director=@Director,

DateReleased=@DateReleased WHERE Id=@id”

Runat=”server”>

<asp:Parameter Name=”Title”

Type=”String” Size=”100” DefaultValue=”Untitled” />

<asp:Parameter Name=”Director”

Type=”String” Size=”100” DefaultValue=”Alan Smithee” />

<asp:Parameter Name=”DateReleased” Type=”DateTime” />

<asp:Parameter Name=”id” Type=”int32” />

</UpdateParameters>

</asp:SqlDataSource>

</div>

</form>

</body>

</html>

In Listing 9.16, each of the parameters used by the update command is provided with

an explicit data type For example, the DateReleased parameter is declared to be a

DateTime parameter (If you didn’t assign an explicit type to this parameter, it would

default to a string.)

Furthermore, the Title and Director parameters are provided with default values If you

edit a movie record and do not supply a title or director, the default values are used

NOTE

Another situation in which explicitly declaring Parameter objects is useful is when you

need to explicitly order the parameters For example, the order of parameters is

impor-tant when you use the OLE DB provider with Microsoft Access

Trang 7

Using the ASP.NET ControlParameter Object

You use the ControlParameter object to represent the value of a control property You can

use it to represent the value of any control contained in the same page as the

SqlDataSource control

The ControlParameter object includes all the properties of the Parameter object and these

additional properties:

ControlID—The ID of the control that the parameter represents

PropertyName—The name of the property that the parameter represents

For example, the page in Listing 9.17 includes a DropDownList control and a DetailsView

control When you select a movie from the DropDownList, details for the movie display in

the DetailsView control (see Figure 9.10)

LISTING 9.17 ShowControlParameter.aspx

<title>Show Control Parameter</title>

FIGURE 9.10 Show matching movies for each movie category

Trang 8

</head>

<body>

<div>

<asp:DropDownList

id=”ddlMovies”

DataTextField=”Title”

DataValueField=”Id”

<asp:Button

id=”btnSelect”

Text=”Select”

<hr />

<asp:DetailsView

id=”dtlMovie”

DataSourceID=”srcMovieDetails”

<asp:SqlDataSource

id=”srcMovies”

SelectCommand=”SELECT Id,Title FROM Movies”

<asp:SqlDataSource

id=”srcMovieDetails”

SelectCommand=”SELECT * FROM Movies

WHERE Id=@Id”

Runat=”server”>

<asp:ControlParameter Name=”Id” ControlID=”ddlMovies”

PropertyName=”SelectedValue” />

</SelectParameters>

</asp:SqlDataSource>

</div>

</form>

</body>

</html>

Trang 9

The second SqlDataSource control in Listing 9.17 includes a ControlParameter object

The ControlParameter represents the ID of the selected movie in the DropDownList

control

When using a ControlParameter, you must always set the value of the ControlID property

to point to a control on the page On the other hand, you are not always required to set

the PropertyName property If you do not set PropertyName, the ControlParameter object

automatically looks for a property decorated with the ControlValueProperty attribute

Because the SelectedValue property of the DropDownList control is decorated with this

attribute, you do not need to set this property in Listing 9.17

Because the Page class derives from the control class, you can use the ControlParameter

object to represent the value of a Page property

For example, the page in Listing 9.18 contains a simple guestbook that connects to a

data-base called “GuestBook” When a user adds a new entry to the guestbook, the user’s

remote IP address is saved automatically with the guestbook entry (see Figure 9.11)

FIGURE 9.11 Saving an IP address in guest book entries

Trang 10

LISTING 9.18 ShowPageControlParameter.aspx

public string IPAddress

{

get { return Request.UserHostAddress; }

}

</script>

<title>Show Page Control Parameter</title>

</head>

<body>

<div>

<asp:FormView

id=”frmGuestBook”

DataSourceID=”srcGuestBook”

DefaultMode=”Insert”

runat=”server”>

<asp:Label

id=”lblName”

Text=”Your Name:”

AssociatedControlID=”txtName”

<asp:TextBox

id=”txtName”

Text=’<%# Bind(“Name”) %>’

<asp:Label

id=”Label1”

Text=”Your Comments:”

AssociatedControlID=”txtComments”

<br />

<asp:TextBox

id=”txtComments”

Định dạng
Số trang	10
Dung lượng	585,27 KB