複合 Web 控制項範例

更新：2007 年 11 月

本範例將示範如何建立名稱為 Register 的控制項，這個控制項會示範實作複合 ASP.NET 伺服器控制項所需之主要步驟。複合控制項 (Composite Control) 使用子控制項建立使用者介面 (UI)，並執行其他邏輯。由於複合控制項在功能上依賴子控制項，比起自行實作所有控制項的功能來說，開發複合控制項相對上簡單多了。

在此範例中，Register 控制項會使用子控制項建立使用者介面 (UI)，方便輸入使用者資訊以登錄網站。UI 由兩個 TextBox 控制項 (一個用於輸入使用者名稱，而另一個用於輸入使用者的電子郵件地址) 和送出資訊的 Button 控制項所組成。Register 也會讓 RequiredFieldValidator 控制項與兩個 TextBox 控制項產生關聯，以確定使用者已輸入名稱和電子郵件地址。Button 控制項的 Click 事件會引發為 Register 控制項的 Submit 事件。

Register 控制項的行為依賴子控制項的內建功能。例如，Register 依賴 TextBox 控制項處理回傳資料、對於回傳事件依賴 Button 控制項，而對於驗證則依賴 RequiredFieldValidator 控制項。

Register 控制項的程式碼會在本主題稍後的「程式碼討論」章節中說明。檢查 Register 控制項的程式碼時，您會注意到大多數程式碼都與建立和管理子控制項相關。

Register 控制項的程式碼清單

' Register.vb
Option Strict On
Imports System
Imports System.ComponentModel
Imports System.Drawing
Imports System.Security.Permissions
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls

Namespace Samples.AspNet.VB.Controls
    < _
    AspNetHostingPermission(SecurityAction.Demand, _
        Level:=AspNetHostingPermissionLevel.Minimal), _
    AspNetHostingPermission(SecurityAction.InheritanceDemand, _
        Level:=AspNetHostingPermissionLevel.Minimal), _
    DefaultEvent("Submit"), _
    DefaultProperty("ButtonText"), _
    ToolboxData("<{0}:Register runat=""server""> </{0}:Register>") _
    > _
    Public Class Register
        Inherits CompositeControl

        Private submitButton As Button
        Private nameTextBox As TextBox
        Private nameLabel As Label
        Private emailTextBox As TextBox
        Private emailLabel As Label
        Private emailValidator As RequiredFieldValidator
        Private nameValidator As RequiredFieldValidator

        Private Shared ReadOnly EventSubmitKey As New Object()

        ' The following properties are delegated to child controls.
        < _
        Bindable(True), _
        Category("Appearance"), _
        DefaultValue(""), _
        Description("The text to display on the button.") _
        > _
        Public Property ButtonText() As String
            Get
                EnsureChildControls()
                Return submitButton.Text
            End Get
            Set(ByVal value As String)
                EnsureChildControls()
                submitButton.Text = value
            End Set
        End Property

        < _
        Bindable(True), _
        Category("Default"), _
        DefaultValue(""), _
        Description("The user name.") _
        > _
        Public Property Name() As String
            Get
                EnsureChildControls()
                Return nameTextBox.Text
            End Get
            Set(ByVal value As String)
                EnsureChildControls()
                nameTextBox.Text = value
            End Set
        End Property

        < _
        Bindable(True), _
        Category("Appearance"), _
        DefaultValue(""), _
        Description("Error message for the name validator.") _
        > _
        Public Property NameErrorMessage() As String
            Get
                EnsureChildControls()
                Return nameValidator.ErrorMessage
            End Get
            Set(ByVal value As String)
                EnsureChildControls()
                nameValidator.ErrorMessage = value
                nameValidator.ToolTip = value
            End Set
        End Property

        < _
        Bindable(True), _
        Category("Appearance"), _
        DefaultValue(""), _
        Description("The text for the name label.") _
        > _
        Public Property NameLabelText() As String
            Get
                EnsureChildControls()
                Return nameLabel.Text
            End Get
            Set(ByVal value As String)
                EnsureChildControls()
                nameLabel.Text = value
            End Set
        End Property

        < _
        Bindable(True), _
        Category("Default"), _
        DefaultValue(""), _
        Description("The e-mail address.") _
        > _
        Public Property Email() As String
            Get
                EnsureChildControls()
                Return emailTextBox.Text
            End Get
            Set(ByVal value As String)
                EnsureChildControls()
                emailTextBox.Text = value
            End Set
        End Property

        < _
        Bindable(True), _
        Category("Appearance"), _
        DefaultValue(""), _
        Description("Error message for the e-mail validator.") _
        > _
        Public Property EmailErrorMessage() As String
            Get
                EnsureChildControls()
                Return emailValidator.ErrorMessage
            End Get
            Set(ByVal value As String)
                EnsureChildControls()
                emailValidator.ErrorMessage = value
                emailValidator.ToolTip = value
            End Set
        End Property

        < _
        Bindable(True), _
        Category("Appearance"), _
        DefaultValue(""), _
        Description("The text for the e-mail label.") _
        > _
        Public Property EmailLabelText() As String
            Get
                EnsureChildControls()
                Return emailLabel.Text
            End Get
            Set(ByVal value As String)
                EnsureChildControls()
                emailLabel.Text = value
            End Set
        End Property

        ' The Submit event.
        < _
        Category("Action"), _
        Description("Raised when the user clicks the button.") _
        > _
        Public Custom Event Submit As EventHandler
            AddHandler(ByVal value As EventHandler)
                Events.AddHandler(EventSubmitKey, value)
            End AddHandler
            RemoveHandler(ByVal value As EventHandler)
                Events.RemoveHandler(EventSubmitKey, value)
            End RemoveHandler
            RaiseEvent(ByVal sender As Object, _
                ByVal e As System.EventArgs)
                CType(Events(EventSubmitKey), _
                    EventHandler).Invoke(sender, e)
            End RaiseEvent
        End Event

        ' The method that raises the Submit event.
        Protected Overridable Sub OnSubmit(ByVal e As EventArgs)
            Dim submitHandler As EventHandler = _
                CType(Events(EventSubmitKey), EventHandler)
            If submitHandler IsNot Nothing Then
                submitHandler(Me, e)
            End If
        End Sub

        ' Handles the Click event of the Button and raises
        ' the Submit event.
        Private Sub submitButton_Click(ByVal source As Object, _
            ByVal e As EventArgs)
            OnSubmit(EventArgs.Empty)
        End Sub

        Protected Overrides Sub CreateChildControls()
            Controls.Clear()

            nameLabel = New Label()

            nameTextBox = New TextBox()
            nameTextBox.ID = "nameTextBox"

            nameValidator = New RequiredFieldValidator()
            nameValidator.ID = "validator1"
            nameValidator.ControlToValidate = nameTextBox.ID
            nameValidator.Text = "Failed validation."
            nameValidator.Display = ValidatorDisplay.Static

            emailLabel = New Label()

            emailTextBox = New TextBox()
            emailTextBox.ID = "emailTextBox"

            emailValidator = New RequiredFieldValidator()
            emailValidator.ID = "validator2"
            emailValidator.ControlToValidate = emailTextBox.ID
            emailValidator.Text = "Failed validation."
            emailValidator.Display = ValidatorDisplay.Static

            submitButton = New Button()
            submitButton.ID = "button1"
            AddHandler submitButton.Click, _
                AddressOf submitButton_Click

            Me.Controls.Add(nameLabel)
            Me.Controls.Add(nameTextBox)
            Me.Controls.Add(nameValidator)
            Me.Controls.Add(emailLabel)
            Me.Controls.Add(emailTextBox)
            Me.Controls.Add(emailValidator)
            Me.Controls.Add(submitButton)
        End Sub

        Protected Overrides Sub Render(ByVal writer As HtmlTextWriter)
            AddAttributesToRender(writer)

            writer.AddAttribute(HtmlTextWriterAttribute.Cellpadding, _
                "1", False)
            writer.RenderBeginTag(HtmlTextWriterTag.Table)

            writer.RenderBeginTag(HtmlTextWriterTag.Tr)
            writer.RenderBeginTag(HtmlTextWriterTag.Td)
            nameLabel.RenderControl(writer)
            writer.RenderEndTag()
            writer.RenderBeginTag(HtmlTextWriterTag.Td)
            nameTextBox.RenderControl(writer)
            writer.RenderEndTag()
            writer.RenderBeginTag(HtmlTextWriterTag.Td)
            nameValidator.RenderControl(writer)
            writer.RenderEndTag()
            writer.RenderEndTag()

            writer.RenderBeginTag(HtmlTextWriterTag.Tr)
            writer.RenderBeginTag(HtmlTextWriterTag.Td)
            emailLabel.RenderControl(writer)
            writer.RenderEndTag()
            writer.RenderBeginTag(HtmlTextWriterTag.Td)
            emailTextBox.RenderControl(writer)
            writer.RenderEndTag()
            writer.RenderBeginTag(HtmlTextWriterTag.Td)
            emailValidator.RenderControl(writer)
            writer.RenderEndTag()
            writer.RenderEndTag()

            writer.RenderBeginTag(HtmlTextWriterTag.Tr)
            writer.AddAttribute(HtmlTextWriterAttribute.Colspan, _
                "2", False)
            writer.AddAttribute(HtmlTextWriterAttribute.Align, _
                "right", False)
            writer.RenderBeginTag(HtmlTextWriterTag.Td)
            submitButton.RenderControl(writer)
            writer.RenderEndTag()
            writer.RenderBeginTag(HtmlTextWriterTag.Td)
            writer.Write("&nbsp")
            writer.RenderEndTag()
            writer.RenderEndTag()

            writer.RenderEndTag()
        End Sub

        Protected Overrides Sub RecreateChildControls()
            EnsureChildControls()
        End Sub

    End Class
End Namespace

// Register.cs
using System;
using System.ComponentModel;
using System.Drawing;
using System.Security.Permissions;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace Samples.AspNet.CS.Controls
{
    [
    AspNetHostingPermission(SecurityAction.Demand,
        Level = AspNetHostingPermissionLevel.Minimal),
    AspNetHostingPermission(SecurityAction.InheritanceDemand, 
        Level=AspNetHostingPermissionLevel.Minimal),
    DefaultEvent("Submit"),
    DefaultProperty("ButtonText"),
    ToolboxData("<{0}:Register runat=\"server\"> </{0}:Register>"),
    ]
    public class Register : CompositeControl
    {
        private Button submitButton;
        private TextBox nameTextBox;
        private Label nameLabel;
        private TextBox emailTextBox;
        private Label emailLabel;
        private RequiredFieldValidator emailValidator;
        private RequiredFieldValidator nameValidator;

        private static readonly object EventSubmitKey = 
            new object();

        // The following properties are delegated to 
        // child controls.
        [
        Bindable(true),
        Category("Appearance"),
        DefaultValue(""),
        Description("The text to display on the button.")
        ]
        public string ButtonText
        {
            get
            {
                EnsureChildControls();
                return submitButton.Text;
            }
            set
            {
                EnsureChildControls();
                submitButton.Text = value;
            }
        }

        [
        Bindable(true),
        Category("Default"),
        DefaultValue(""),
        Description("The user name.")
        ]
        public string Name
        {
            get
            {
                EnsureChildControls();
                return nameTextBox.Text;
            }
            set
            {
                EnsureChildControls();
                nameTextBox.Text = value;
            }
        }

        [
        Bindable(true),
        Category("Appearance"),
        DefaultValue(""),
        Description(
            "Error message for the name validator.")
        ]
        public string NameErrorMessage
        {
            get
            {
                EnsureChildControls();
                return nameValidator.ErrorMessage;
            }
            set
            {
                EnsureChildControls();
                nameValidator.ErrorMessage = value;
                nameValidator.ToolTip = value;
            }
        }

        [
        Bindable(true),
        Category("Appearance"),
        DefaultValue(""),
        Description("The text for the name label.")
        ]
        public string NameLabelText
        {
            get
            {
                EnsureChildControls();
                return nameLabel.Text;
            }
            set
            {
                EnsureChildControls();
                nameLabel.Text = value;
            }
        }

        [
        Bindable(true),
        Category("Default"),
        DefaultValue(""),
        Description("The e-mail address.")
        ]
        public string Email
        {
            get
            {
                EnsureChildControls();
                return emailTextBox.Text;
            }
            set
            {
                EnsureChildControls();
                emailTextBox.Text = value;
            }
        }

        [
        Bindable(true),
        Category("Appearance"),
        DefaultValue(""),
        Description(
            "Error message for the e-mail validator.")
        ]
        public string EmailErrorMessage
        {
            get
            {
                EnsureChildControls();
                return emailValidator.ErrorMessage;
            }
            set
            {
                EnsureChildControls();
                emailValidator.ErrorMessage = value;
                emailValidator.ToolTip = value;
            }
        }

        [
        Bindable(true),
        Category("Appearance"),
        DefaultValue(""),
        Description("The text for the e-mail label.")
        ]
        public string EmailLabelText
        {
            get
            {
                EnsureChildControls();
                return emailLabel.Text;
            }
            set
            {
                EnsureChildControls();
                emailLabel.Text = value;

            }
        }

        // The Submit event.
        [
        Category("Action"),
        Description("Raised when the user clicks the button.")
        ]
        public event EventHandler Submit
        {
            add
            {
                Events.AddHandler(EventSubmitKey, value);
            }
            remove
            {
                Events.RemoveHandler(EventSubmitKey, value);
            }
        }

        // The method that raises the Submit event.
        protected virtual void OnSubmit(EventArgs e)
        {
            EventHandler SubmitHandler =
                (EventHandler)Events[EventSubmitKey];
            if (SubmitHandler != null)
            {
                SubmitHandler(this, e);
            }
        }

        // Handles the Click event of the Button and raises
        // the Submit event.
        private void _button_Click(object source, EventArgs e)
        {
            OnSubmit(EventArgs.Empty);
        }

        protected override void RecreateChildControls()
        {
            EnsureChildControls();
        }


        protected override void CreateChildControls()
        {
            Controls.Clear();

            nameLabel = new Label();

            nameTextBox = new TextBox();
            nameTextBox.ID = "nameTextBox";

            nameValidator = new RequiredFieldValidator();
            nameValidator.ID = "validator1";
            nameValidator.ControlToValidate = nameTextBox.ID;
            nameValidator.Text = "Failed validation.";
            nameValidator.Display = ValidatorDisplay.Static;

            emailLabel = new Label();

            emailTextBox = new TextBox();
            emailTextBox.ID = "emailTextBox";

            emailValidator = new RequiredFieldValidator();
            emailValidator.ID = "validator2";
            emailValidator.ControlToValidate = 
                emailTextBox.ID;
            emailValidator.Text = "Failed validation.";
            emailValidator.Display = ValidatorDisplay.Static;

            submitButton = new Button();
            submitButton.ID = "button1";
            submitButton.Click 
                += new EventHandler(_button_Click);

            this.Controls.Add(nameLabel);
            this.Controls.Add(nameTextBox);
            this.Controls.Add(nameValidator);
            this.Controls.Add(emailLabel);
            this.Controls.Add(emailTextBox);
            this.Controls.Add(emailValidator);
            this.Controls.Add(submitButton);
        }


        protected override void Render(HtmlTextWriter writer)
        {
            AddAttributesToRender(writer);

            writer.AddAttribute(
                HtmlTextWriterAttribute.Cellpadding,
                "1", false);
            writer.RenderBeginTag(HtmlTextWriterTag.Table);

            writer.RenderBeginTag(HtmlTextWriterTag.Tr);
            writer.RenderBeginTag(HtmlTextWriterTag.Td);
            nameLabel.RenderControl(writer);
            writer.RenderEndTag();
            writer.RenderBeginTag(HtmlTextWriterTag.Td);
            nameTextBox.RenderControl(writer);
            writer.RenderEndTag();
            writer.RenderBeginTag(HtmlTextWriterTag.Td);
            nameValidator.RenderControl(writer);
            writer.RenderEndTag();
            writer.RenderEndTag();

            writer.RenderBeginTag(HtmlTextWriterTag.Tr);
            writer.RenderBeginTag(HtmlTextWriterTag.Td);
            emailLabel.RenderControl(writer);
            writer.RenderEndTag();
            writer.RenderBeginTag(HtmlTextWriterTag.Td);
            emailTextBox.RenderControl(writer);
            writer.RenderEndTag();
            writer.RenderBeginTag(HtmlTextWriterTag.Td);
            emailValidator.RenderControl(writer);
            writer.RenderEndTag();
            writer.RenderEndTag();

            writer.RenderBeginTag(HtmlTextWriterTag.Tr);
            writer.AddAttribute(
                HtmlTextWriterAttribute.Colspan, 
                "2", false);
            writer.AddAttribute(
                HtmlTextWriterAttribute.Align, 
                "right", false);
            writer.RenderBeginTag(HtmlTextWriterTag.Td);
            submitButton.RenderControl(writer);
            writer.RenderEndTag();
            writer.RenderBeginTag(HtmlTextWriterTag.Td);
            writer.Write("&nbsp;");
            writer.RenderEndTag();
            writer.RenderEndTag();

            writer.RenderEndTag();
        }
    }
}

程式碼討論

Register 控制項會執行下列所有複合控制項通用的工作：

• 衍生自 CompositeControl 類別。

• 藉由覆寫 CreateChildControls 方法建立子控制項。

CompositeControl 類別會實作所有複合控制項需要的一般功能。此類別也具有相關聯的控制項設計工具，可確定在視覺化設計工具 (Visual Designer) 的設計介面上顯示子控制項。

注意事項：
CompositeControl 類別是 ASP.NET 2.0 的新功能。如果您已在 ASP.NET 1.0 版或 1.1 版中建立自訂控制項，必須實作 INamingContainer 介面以建立子控制項的新命名範圍。此外，您必須覆寫 Controls 屬性並叫用 (Invoke) EnsureChildControls 方法。在 ASP.NET 2.0 中，是由 CompositeControl 類別執行這些動作和其他步驟。

您應該在 CreateChildControls 方法中建立子控制項，而不是在 OnInit 或其他生命週期階段中建立。伺服器控制項架構是依賴每次需要 Controls 集合時對 CreateChildControls 的呼叫，例如在資料繫結期間 (適用的話)。

Register 控制項也會說明如何公開 (Expose) 子控制項的屬性做為最上層屬性。當您希望允許網頁開發人員存取子控制項的屬性時，這樣做將會很實用。例如，Register 會公開 Button 子控制項的 Text 屬性做為自己的 ButtonText 屬性，如範例中描繪的下列程式碼所示：

< _
Bindable(True), _
Category("Appearance"), _
DefaultValue(""), _
Description("The text to display on the button.") _
> _
Public Property ButtonText() As String
    Get
        EnsureChildControls()
        Return submitButton.Text
    End Get
    Set(ByVal value As String)
        EnsureChildControls()
        submitButton.Text = value
    End Set
End Property

[
Bindable(true),
Category("Appearance"),
DefaultValue(""),
Description("The text to display on the button.")
]
public string ButtonText
{
    get
    {
        EnsureChildControls();
        return submitButton.Text;
    }
    set
    {
        EnsureChildControls();
        submitButton.Text = value;
    }
}

Register 控制項不會將 ButtonText 或其他委派 (Delegate) 至子控制項的屬性存放至檢視狀態，因為子控制項會使用檢視狀態存放這些屬性。如需如何管理未委派至子控制項之屬性狀態的詳細資訊，請參閱伺服器控制項屬性範例。這個主題包含使用 ViewState 字典存放簡單屬性，以及對具有子屬性之屬性實作自訂狀態管理的詳細資訊。

Register 控制項顯示如何從子控制項的事件處理常式引發事件。Register 控制項透過將處理常式附加至 Button 子控制項的 Click 事件，可定義名為 Submit 的事件並引發事件。

Register 控制項的測試頁

下列範例示範使用 Register 控制項的 ASP.NET Web 網頁。

<%@ Page Language="VB"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script >
    Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
        Label1.Visible = False
    End Sub

    Sub Register_Submit(ByVal sender As Object, ByVal e As EventArgs)
        ' The application developer can implement
        ' logic here to enter registration data into
        ' a database or write a cookie
        ' on the user's computer.
        ' This example merely writes a message
        ' using the Label control on the page.
        Label1.Text = String.Format( _
            "Thank you, {0}! You are registered.", Register1.Name)
        Label1.Visible = True
        Register1.Visible = False
    End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
  <head id="Head1" >
    <title>
      Register Control Test Page
    </title>
  </head>
  <body>
    <form id="form1" >
      <aspSample:Register ButtonText="Submit" 
        OnSubmit="Register_Submit" ID="Register1"
        Runat="server" NameLabelText="Name:" EmailLabelText="Email:" 
        EmailErrorMessage="You must enter your e-mail address." 
        NameErrorMessage="You must enter your name." />
       <br />
      <asp:Label ID="Label1" Runat="server" Text="Label">
      </asp:Label>
      <asp:ValidationSummary ID="ValidationSummary1" 
        Runat="server" DisplayMode="List" />
    </form>
  </body>
</html>

<%@ Page Language="C#"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script >
  void Page_Load(object sender, EventArgs e)
  {
    Label1.Visible = false;
  }
  void Register_Submit(object sender, EventArgs e)
  {
    // The application developer can implement
    // logic here to enter registration data into
    // a database or write a cookie
    // on the user's computer.
    // This example merely writes a message
    // using the Label control on the page.
    Label1.Text = String.Format(
        "Thank you, {0}! You are registered.",Register1.Name);
    Label1.Visible = true;
    Register1.Visible = false;
  }
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
  <head id="Head1" >
    <title>
      Register Control Test Page
    </title>
  </head>
  <body>
    <form id="form1" >
      <aspSample:Register ButtonText="Register" 
        OnSubmit="Register_Submit" ID="Register1"
        Runat="server" NameLabelText="Name:" 
        EmailLabelText="Email:" 
        EmailErrorMessage="You must enter your e-mail address." 
        NameErrorMessage="You must enter your name." />
       <br />
      <asp:Label ID="Label1" Runat="server" Text="Label">
      </asp:Label>
      <asp:ValidationSummary ID="ValidationSummary1" 
        Runat="server" DisplayMode="List" />
    </form>
  </body>
</html>

建置及使用範例

如需編譯及使用自訂控制項範例的詳細資訊，請參閱建置自訂伺服器控制項範例。

請參閱

其他資源

開發自訂的 ASP.NET 伺服器控制項