为自定义WebControl绑定EventHandler

Question

I have a Custom Web Control that is derived from Panel . In my aspx markup for the control, I have a public event EventHandler called SubmitButtonClicked

<cc1:CreditCard ID="CustomCreditCardPopupPanel" runat="server" 
SubmitButtonClicked="CustomCreditCardPopupPanel_SubmitClick">  </cc1:CreditCard>

Here is the code for the custom web control (Shortened for clarity). When the web control is instantiated, the EventHandler SubmitButtonClicked is always null. How do I pass in the name of the event that I want to bind to the Button called BtnSubmit ?

[DefaultProperty("Text"),
    AspNetHostingPermission(SecurityAction.Demand,
    Level = AspNetHostingPermissionLevel.Minimal),
    AspNetHostingPermission(SecurityAction.InheritanceDemand,
    Level = AspNetHostingPermissionLevel.Minimal),
    ToolboxData("<{0}:CreditCard runat=server></{0}:CreditCard>")
]
public class CreditCard: Panel {

  public event EventHandler SubmitButtonClicked;
  public Button BtnSubmit { get; set; }

  protected override void OnPreRender(EventArgs e) {
    base.OnPreRender(e);
    this.BtnSubmit.Click += new EventHandler(SubmitButtonClicked); // SubmitButtonClicked is always null
  }

  protected void SubmitButtonClicked_Clicked(Object sender, EventArgs e) {

    if (SubmitButtonClicked != null) {

        SubmitButtonClicked(sender, e);
    }

 }

}

Answer 1

You must have

this.BtnSubmit.Click += new EventHandler(SubmitButtonClicked_Clicked);

And also, OnPreRender event could be too late. Maybe you should assign the button event in Init, or Load event

Answer 2

Turns out that the best way to handle what I want to do is to derive my class from CompositeControl.

MSDN CompositeControl

Example from Link:

// 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();
        }
    }
}