ASP.NET 2.0服务器控件之复合控件概述(2)

// 实现属性EmailErrorMessage

[
　Bindable(true),
　Category("Appearance"),
　DefaultValue(""),
　Description("邮件地址验证错误信息.")
]

public string EmailErrorMessage {
　get {
　　EnsureChildControls();
　　return emailValidator.ErrorMessage;
　}
　set {
　　EnsureChildControls();
　　emailValidator.ErrorMessage = value;
　　emailValidator.ToolTip = value;
　}
}

// 实现属性EmailLabelText

[
　Bindable(true),
　Category("Appearance"),
　DefaultValue(""),
　Description("电子邮件文本框旁的文字.")
]

public string EmailLabelText {
　get {
　　EnsureChildControls();
　　return emailLabel.Text;
　}
　set {
　　EnsureChildControls();
　　emailLabel.Text = value;
　}
}

// 重写ICompositeControlDesignerAccessor接口的RecreateChildContrls方法

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

// 重写Control基类的CreateChildControls方法

protected override void CreateChildControls() {
　// 清除所有子控件
　Controls.Clear();
　nameLabel = new Label();
　nameTextBox = new TextBox();
　nameTextBox.ID = "nameTextBox";
　nameValidator = new RequiredFieldValidator();
　nameValidator.ID = "validator1";
　nameValidator.ControlToValidate = nameTextBox.ID;
　nameValidator.Text = NameErrorMessage;
　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 = EmailErrorMessage;
　emailValidator.Display = ValidatorDisplay.Static;
　submitButton = new Button();
　submitButton.ID = "button1";
　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);
}

// 重写Render方法

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(" ");
　writer.RenderEndTag();
　writer.RenderEndTag();
　writer.RenderEndTag();
}
}
}
　　以上列举了复合控件类Register的源代码。虽然代码有些冗长，然而还是比较容易理解的。下图1列举了Register类结构图。

图1 类结构图

　　如图1并结合代码可知，Register类继承自CompositeControl基类，其实现了7个属性和3个方法。属性包括ButtonText、Email、EmailErrorMessage、EmailLabelText、Name、NameErrorMessage和NameLabelText。这些属性通过命名，相信读者基本可以了解其意义。

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