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ptg 324 CHAPTER 7 Creating Custom Controls with User Controls break; } } </script> <html xmlns=”http://www.w3.org/1999/xhtml” > <head id=”Head1” runat=”server”> <style type=”text/css”> html { font:14px Arial,Sans-Serif; } </style> <title>Web Survey</title> </head> <body> <form id=”form1” runat=”server”> <div> <asp:Label id=”lblLanguage” Text=”What language do you use to develop Web applications?” Runat=”server” /> <br /> <asp:DropDownList id=”ddlLanguage” ToolTip=”Web application language (reloads form)” AutoPostBack=”true” Runat=”server”> <asp:ListItem Text=”Select Language” /> <asp:ListItem Text=”ASP Classic” /> <asp:ListItem Text=”ASP.NET” /> </asp:DropDownList> <br /><br /> <asp:PlaceHolder id=”PlaceHolder1” Runat=”server” /> <asp:Button id=”btnSubmit” Text=”Submit” OnClick=”btnSubmit_Click” Runat=”server” /> From the Library of Wow! eBook ptg 325 Dynamically Loading User Controls 7 <hr /> <asp:Literal id=”ltlResults” Runat=”server” /> </div> </form> </body> </html> WEB STANDARDS NOTE The DropDownList control in Listing 7.15 reloads the page automatically when you select a new option. You should never reload a page without warning the user because this can be confusing for someone who uses an assistive device such as a screen reader. In Listing 7.15, a warning is added to the ToolTip property of the DropDownList control. Depending on the user’s selection from the DropDownList control, one of two User controls is loaded in the Page_Load() event handler: ASPSurvey.ascx or ASPNetSurvey.ascx. These controls are contained in Listing 7.16 and Listing 7.17. When you submit the survey form, the btnSubmit_Click() method executes. This method casts the User control loaded in the form to the correct type. It casts the User control to either the ASPSurvey or the ASPNetSurvey type. The page in Listing 7.16 includes two <%@ Reference %> directives. These reference direc- tives enable you to cast the User control to the correct type so that you can access custom properties of the control such as the KnowSlow and KnowOutdated properties. LISTING 7.16 ASPSurvey.ascx <%@ Control Language=”C#” ClassName=”ASPSurvey” %> <script runat=”server”> public bool KnowSlow { get { return chkSlow.Checked; } } public bool KnowOutdated { From the Library of Wow! eBook ptg 326 CHAPTER 7 Creating Custom Controls with User Controls get { return chkOutdated.Checked; } } </script> <asp:CheckBox id=”chkSlow” Text=”Did you know that ASP Classic is slow?” Runat=”server” /> <br /><br /> <asp:CheckBox id=”chkOutdated” Text=”Did you know that ASP Classic is outdated?” Runat=”server” /> <br /><br /> LISTING 7.17 ASPNetSurvey.ascx <%@ Control Language=”C#” ClassName=”ASPNetSurvey” %> <script runat=”server”> public bool KnowFast { get { return chkFast.Checked; } } public bool KnowNewest { get { return chkNewest.Checked; } } </script> <asp:CheckBox id=”chkFast” Text=”Did you know that ASP.NET is fast?” Runat=”server” /> <br /><br /> <asp:CheckBox id=”chkNewest” From the Library of Wow! eBook ptg 327 Dynamically Loading User Controls 7 Text=”Did you know that ASP.NET is the newest Microsoft technology for building Web applications?” Runat=”server” /> <br /><br /> Creating a Multipage Wizard This final section discusses how you can create a multipage wizard by dynamically loading different User controls into the same page. This is going to be a complicated sample, but it is a realistic sample of situations when you would want to load User controls dynamically (see Figure 7.6). FIGURE 7.6 Displaying a wizard with a series of User controls. Imagine that you must create a form with 200 questions in it. Displaying all 200 ques- tions to a user in a single form would be overwhelming. Instead, it makes more sense to break the form into multiple pages. Each page of questions can be represented with a User control. First, you need to define an interface, named the IWizardStep interface, which all the User controls will implement. An interface enables you to know, in advance, that a User control supports a particular set of properties or methods. From the Library of Wow! eBook ptg 328 CHAPTER 7 Creating Custom Controls with User Controls NOTE You need to add the interface in Listing 7.18 to your ap pl ic at ion’s App_Code folder. In Visual Web Developer, create the interface by selecting Website, Add New Item, select Class. Visual Web Developer prompts you to create the App_Code folder. The IWizardStep interface is contained in Listing 7.18. LISTING 7.18 IWizardStep.cs public interface IWizardStep { void LoadStep(); bool NextStep(); } The interface in Listing 7.18 contains two methods: LoadStep() and NextStep(). The LoadStep() method is called when a User control is first loaded. The NextStep() method is called when the Next button is clicked in the wizard. The NextStep() method returns a Boolean value. If the NextStep() method returns the value False, the user doesn’t advance to the next wizard step. This wizard consists of the three wizard steps contained in Listing 7.19, Listing 7.20, and Listing 7.21. LISTING 7.19 WizardSteps\Step1.ascx <%@ Control Language=”C#” ClassName=”Step1” %> <%@ Implements Interface=”IWizardStep” %> <script runat=”server”> public void LoadStep() { if (Session[“FirstName”] != null) txtFirstName.Text = (string)Session[“FirstName”]; if (Session[“LastName”] != null) txtLastName.Text = (string)Session[“LastName”]; } public bool NextStep() { if (Page.IsValid) { Session[“FirstName”] = txtFirstName.Text; From the Library of Wow! eBook ptg 329 Dynamically Loading User Controls 7 Session[“LastName”] = txtLastName.Text; return true; } return false; } </script> <h1>Step 1</h1> <asp:Label id=”lblFirstName” Text=”First Name:” AssociatedControlID=”txtFirstName” Runat=”server” /> <asp:RequiredFieldValidator id=”reqFirstName” Text=”(required)” ControlToValidate=”txtFirstName” Runat=”server” /> <br /> <asp:TextBox id=”txtFirstName” Runat=”server” /> <br /><br /> <asp:Label id=”lblLastName” Text=”Last Name:” AssociatedControlID=”txtLastName” Runat=”server” /> <asp:RequiredFieldValidator id=”reqLastName” Text=”(required)” ControlToValidate=”txtLastName” Runat=”server” /> <br /> <asp:TextBox id=”txtLastName” Runat=”server” /> The wizard step in Listing 7.19 contains a simple form that contains Textbox controls for the user’s first and last name. Both TextBox controls are validated with RequiredFieldValidator controls. The User control in Listing 7.19 implements the IWizardStep interface. It contains an <%@ Implements %> directive at the top of the control. From the Library of Wow! eBook ptg 330 CHAPTER 7 Creating Custom Controls with User Controls The LoadStep() method assigns values to the txtFirstName and txtLastName TextBox controls from Session state. The NextStep() method grabs the values from the txtFirstName and txtLastName TextBox controls and assigns the values to Session state. The second step of the Wizard is contained in Listing 7.20. LISTING 7.20 WizardSteps\Step2.ascx <%@ Control Language=”C#” ClassName=”Step2” %> <%@ Implements Interface=”IWizardStep” %> <script runat=”server”> public void LoadStep() { if (Session[“FavoriteColor”] != null) txtFavoriteColor.Text = (string)Session[“FavoriteColor”]; } public bool NextStep() { if (Page.IsValid) { Session[“FavoriteColor”] = txtFavoriteColor.Text; return true; } return false; } </script> <h1>Step 2</h1> <asp:Label id=”lblFavoriteColor” Text=”Favorite Color:” AssociatedControlID=”txtFavoriteColor” Runat=”server” /> <asp:RequiredFieldValidator id=”reqFavoriteColor” Text=”(required)” ControlToValidate=”txtFavoriteColor” Runat=”server” /> <br /> <asp:TextBox id=”txtFavoriteColor” Runat=”server” /> From the Library of Wow! eBook ptg 331 Dynamically Loading User Controls 7 The User control in Listing 7.20 also implements the IWizardStep interface. In this step, the user enters a favorite color. The final wizard step is contained in Listing 7.21. LISTING 7.21 WizardSteps\Step3.ascx <%@ Control Language=”C#” ClassName=”Step3” %> <%@ Implements Interface=”IWizardStep” %> <script runat=”server”> public void LoadStep() { lblFirstName.Text = (string)Session[“FirstName”]; lblLastName.Text = (string)Session[“LastName”]; lblFavoriteColor.Text = (string)Session[“FavoriteColor”]; } public bool NextStep() { return false; } </script> <h1>Step 3</h1> First Name: <asp:Label id=”lblFirstName” Runat=”server” /> <br /> Last Name: <asp:Label id=”lblLastName” Runat=”server” /> <br /> Favorite Color: <asp:Label id=”lblFavoriteColor” Runat=”server” /> The wizard step in Listing 7.21 displays a summary of answers that the user has provided in the first two wizard steps (see Figure 7.7). It also implements the IWizardStep interface. Because this is the final wizard step, the NextStep() method always returns the value False. From the Library of Wow! eBook ptg 332 CHAPTER 7 Creating Custom Controls with User Controls The page in Listing 7.22 contains the actual wizard. This page loads each of the wizard steps. LISTING 7.22 Wizard.aspx <%@ Page Language=”C#” %> <%@ Import Namespace=”System.Collections.Generic” %> <!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.1//EN” “http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd”> <script runat=”server”> private List<String> _wizardSteps = new List<String>(); private Control _currentStep; /// <summary> /// The current step in the Wizard /// </summary> public int StepIndex { get { if (ViewState[“StepIndex”] == null) return 0; FIGURE 7.7 Displaying the wizard summary step. From the Library of Wow! eBook ptg 333 Dynamically Loading User Controls 7 else return (int)ViewState[“StepIndex”]; } set { ViewState[“StepIndex”] = value; } } /// <summary> /// Load the list of wizard steps and load /// current step /// </summary> void Page_Load() { _wizardSteps.Add(“~/WizardSteps/Step1.ascx”); _wizardSteps.Add(“~/WizardSteps/Step2.ascx”); _wizardSteps.Add(“~/WizardSteps/Step3.ascx”); LoadWizardStep(); } /// <summary> /// Load the current wizard step /// </summary> private void LoadWizardStep() { _currentStep = Page.LoadControl(_wizardSteps[StepIndex]); _currentStep.ID = “ctlWizardStep”; plhWizardStep.Controls.Clear(); plhWizardStep.Controls.Add(_currentStep); ((IWizardStep)_currentStep).LoadStep(); ltlStep.Text = String.Format(“Step {0} of {1}”, StepIndex + 1, _wizardSteps.Count); } /// <summary> /// Disable the Previous and Next /// buttons when appropriate /// </summary> void Page_PreRender() { btnPrevious.Enabled = StepIndex > 0; btnNext.Enabled = StepIndex < _wizardSteps.Count - 1; } From the Library of Wow! eBook . form)” AutoPostBack=”true” Runat=”server”> < ;asp: ListItem Text=”Select Language” /> < ;asp: ListItem Text= ASP Classic” /> < ;asp: ListItem Text= ASP. NET /> < /asp: DropDownList> <br. Page.LoadControl(_wizardSteps[StepIndex]); _currentStep.ID = “ctlWizardStep”; plhWizardStep.Controls.Clear(); plhWizardStep.Controls.Add(_currentStep); ((IWizardStep)_currentStep).LoadStep(); ltlStep.Text = String.Format(“Step. <div> < ;asp: Label id=”lblLanguage” Text=”What language do you use to develop Web applications?” Runat=”server” /> <br /> < ;asp: DropDownList id=”ddlLanguage” ToolTip=”Web application
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