ASP.NET 4 Unleased - p 85 ppsx

LISTING 18.31 FilterMovies.cs using System; using System.Web; using System.Data; using System.Data.SqlClient; using System.Web.Configuration; public class FilterMovies { private readonl

Trang 1

CHAPTER 18 Using the ObjectDataSource Control

LISTING 18.30 ShowFilteredMovies.aspx

<%@ Page Language=”C#” %>

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

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

<title>Show Filtered Movies</title>

</head>

<body>

<div>

<asp:DropDownList

id=”ddlMovieCategory”

DataSourceID=”srcMovieCategories”

DataTextField=”Name”

DataValueField=”Id”

Runat=”server” />

<asp:Button

id=”btnSelect”

Text=”Select”

<hr />

<asp:GridView

id=”grdMovies”

DataSourceID=”srcMovies”

AutoGenerateColumns=”false”

Runat=”server”>

<asp:BoundField

DataField=”Title”

HeaderText=”Movie Title” />

<asp:BoundField

DataField=”Director”

HeaderText=”Movie Director” />

</Columns>

</asp:GridView>

<asp:ObjectDataSource

id=”srcMovieCategories”

TypeName=”FilterMovies”

SelectMethod=”GetMovieCategories”

Trang 2

EnableCaching=”true”

CacheDuration=”Infinite”

id=”srcMovies”

TypeName=”FilterMovies”

SelectMethod=”GetMovies”

EnableCaching=”true”

CacheDuration=”Infinite”

FilterExpression=”CategoryID={0}”

Runat=”server”>

<asp:ControlParameter

Name=”Category”

ControlID=”ddlMovieCategory” />

</FilterParameters>

</asp:ObjectDataSource>

</div>

</form>

</body>

</html>

Both ObjectDataSource controls in Listing 18.30 have caching enabled Furthermore, the

second ObjectDataSource control includes a FilterExpression property that filters the

cached data, using the selected movie category from the DropDownList control

Both ObjectDataSource controls represent the component in Listing 18.31

LISTING 18.31 FilterMovies.cs

using System;

using System.Web;

using System.Data;

using System.Data.SqlClient;

using System.Web.Configuration;

public class FilterMovies

{

private readonly string _conString;

public DataSet GetMovies()

Trang 3

SqlConnection con = new SqlConnection(_conString);

// Initialize DataAdapter

string commandText = “SELECT Title,Director,CategoryId FROM Movies”;

SqlDataAdapter dad = new SqlDataAdapter(commandText, con);

// Return DataSet

DataSet dstMovies = new DataSet();

using (con)

{

dad.Fill(dstMovies);

}

return dstMovies;

}

public DataSet GetMovieCategories()

{

// Initialize connection

// Initialize DataAdapter

string commandText = “SELECT Id,Name FROM MovieCategories”;

SqlDataAdapter dad = new SqlDataAdapter(commandText, con);

// Return DataSet

DataSet dstCategories = new DataSet();

using (con)

{

dad.Fill(dstCategories);

}

return dstCategories;

}

public FilterMovies()

{

_conString =

➥WebConfigurationManager.ConnectionStrings[“Movies”].ConnectionString;

}

The ObjectDataSource enables you to filter data only when the data is represented by a

DataSet, DataTable, or DataView object This means that if you use filtering, the data must

be returned as one of these objects

Trang 4

NOTE

Behind the scenes, the ObjectDataSource control uses the DataView.RowFilter

property to filter database rows You can find detailed documentation on proper filter

syntax by looking up the DataColumn.Expression property in the NET Framework SDK

Documentation

The ObjectDataSource control supports the following events:

Deleting—Occurs immediately before the method represented by the DeleteMethod

property is called

Deleted—Occurs immediately after the method represented by the DeleteMethod

property is called

Inserting—Occurs immediately before the method represented by the InsertMethod

property is called

Inserted—Occurs immediately after the method represented by the InsertMethod

property is called

Selecting—Occurs immediately before the method represented by the SelectMethod

property is called

Selected—Occurs immediately after the method represented by the InsertMethod

property is called

Updating—Occurs immediately before the method represented by the InsertMethod

property is called

Updated—Occurs immediately after the method represented by the InsertMethod

property is called

Filtering—Occurs immediately before the filter expression is evaluated

ObjectCreating—Occurs immediately before the object represented by the

ObjectDataSource control is created

ObjectCreated—Occurs immediately after the object represented by the

ObjectDataSource control is created

ObjectDisposing—Occurs before the object represented by the ObjectDataSource

control is destroyed

Most of these events come in pairs One event happens immediately before a method is

called, and one event happens immediately after a method is called You can handle these

Trang 5

You can also use these events to handle any errors that might result from calling methods

with the ObjectDataSource control

Adding and Modifying Parameters

You can handle the Selecting, Inserting, Updating, and Deleting events to modify the

parameters that are passed to the methods called by the ObjectDataSource control There

are several situations in which you might want to do this

First, if you work with an existing component, you might need to change the names of

the parameters passed to the component For example, instead of passing a parameter

named id to an update method, you might want to rename the parameter to movieId

Second, you might want to pass additional parameters to the method called For example,

you might need to pass the current username, the current IP address, or the current date

and time as a parameter to a method

For example, imagine that you want to create a guestbook and automatically associate the

IP address of the user making an entry with each entry in the guestbook The page in

Listing 18.32 illustrates how you can do this with the help of a FormView control and an

ObjectDataSource control (see Figure 18.9)

FIGURE 18.9 Displaying a guestbook

Trang 6

LISTING 18.32 ShowGuestbook.aspx

protected void srcGuestbook_Inserting(object sender,

➥ObjectDataSourceMethodEventArgs e)

{

e.InputParameters.Add(“IPAddress”, Request.UserHostAddress);

}

</script>

.guestbook td,.guestbook th

{

padding:5px;

font:14px Arial,Sans-Serif;

}

</style>

<title>Show Guestbook</title>

</head>

<body>

<div>

<asp:FormView

id=”frmGuestbook”

DataSourceID=”srcGuestbook”

DefaultMode=”Insert”

Runat=”server”>

<asp:Label

ID=”lblComment”

Text=”Comment:”

AssociatedControlID=”txtComment”

<br />

<asp:TextBox

id=”txtComment”

Text=’<%# Bind(“comment”) %>’

TextMode=”MultiLine”

Trang 7

<br />

<asp:Button

id=”btnInsert”

Text=”Add Entry”

CommandName=”Insert”

</InsertItemTemplate>

</asp:FormView>

<hr />

<asp:GridView

id=”grdGuestbook”

DataSourceID=”srcGuestbook”

CssClass=”guestbook”

id=”srcGuestbook”

TypeName=”Guestbook”

SelectMethod=”GetEntries”

InsertMethod=”AddEntry”

OnInserting=”srcGuestbook_Inserting”

</div>

</form>

</body>

</html>

The page in Listing 18.32 includes an Inserting event handler When the insert method is

called, the IP address of the current user is added to the parameters collection

The ObjectDataSource control in Listing 18.32 is bound to the Guestbook component in

Listing 18.33

LISTING 18.33 Guestbook.cs

using System;

using System.Data;

using System.Data.SqlClient;

using System.Web.Configuration;

public class Guestbook

{

private string _conString;

Trang 8

public SqlDataReader GetEntries()

{

// Initialize command

SqlCommand cmd = new SqlCommand();

cmd.Connection = con;

cmd.CommandText = “SELECT Id,IPAddress,Comment,EntryDate FROM Guestbook”;

// Execute command

con.Open();

return cmd.ExecuteReader(CommandBehavior.CloseConnection);

}

public void AddEntry(string IPAddress, string comment)

{

// Initialize command

SqlCommand cmd = new SqlCommand();

cmd.Connection = con;

cmd.CommandText = “INSERT Guestbook (IPAddress,Comment)” +

“ VALUES (@IPAddress, @Comment)”;

// Add ADO.NET parameters

cmd.Parameters.AddWithValue(“@IPAddress”, IPAddress);

cmd.Parameters.AddWithValue(“@Comment”, comment);

// Execute command

using (con)

{

con.Open();

cmd.ExecuteNonQuery();

}

public Guestbook()

{

_conString =

➥WebConfigurationManager.ConnectionStrings[“Guestbook”].ConnectionString;

}

Trang 9

Realize that you can manipulate the parameters collection in any way that you need You

can change the names, types, or values of any of the parameters

Handling Method Errors

You can handle the Selected, Inserted, Updated, or Deleted events to handle any errors

that might result from calling a method For example, the page in Listing 18.34 handles

the Inserting event to capture any errors raised when the method represented by the

ObjectDataSource control’s InsertMethod property is called

LISTING 18.34 HandleErrors.aspx

protected void srcMovies_Inserted(object sender,

➥ObjectDataSourceStatusEventArgs e)

{

if (e.Exception != null)

{

e.ExceptionHandled = true;

lblError.Text = “Could not insert movie”;

}

</script>

html

{

background-color:silver;

}

.insertForm

{

background-color:white;

}

.insertForm td,.insertForm th

{

padding:10px;

}

.error

{

color:red;

Trang 10

font:bold 14px Arial,Sans-Serif;

}

</style>

<title>Handle Errors</title>

</head>

<body>

<div>

<asp:Label

id=”lblError”

EnableViewState=”false”

CssClass=”error”

<h1>Insert Movie</h1>

<asp:DetailsView

id=”dtlMovies”

DataSourceID=”srcMovies”

DefaultMode=”Insert”

AutoGenerateInsertButton=”true”

AutoGenerateRows=”false”

CssClass=”insertForm”

GridLines=”None”

Runat=”server”>

<asp:BoundField

DataField=”Title”

HeaderText=”Title:”/>

<asp:BoundField

DataField=”Director”

HeaderText=”Director:” />

</Fields>

</asp:DetailsView>

id=”srcMovies”

TypeName=”InsertMovie”

InsertMethod=”Insert”

Runat=”server” OnInserted=”srcMovies_Inserted” />

</div>

</form>

</body>

Tiêu đề	Using The Objectdatasource Control
Trường học	University of Example
Chuyên ngành	Computer Science
Thể loại	Essay
Năm xuất bản	2025
Thành phố	Example City

Định dạng
Số trang	10
Dung lượng	470,36 KB