将click事件处理程序添加到在另一个类中动态创建的按钮

Question

I have a confirmation button being created in a different class to the code behind of the aspx page I want the button interacting with.

Basically, say I have this Confirmation class:

public class Confirmation
{
    public void GenerateButtons()
    {
        Button btnConfirm = new Button();

        btnConfirm.Text = "Confirm";
        btnConfirm.CommandName = "Variable1,Variable2,Variable3";

        _Default def = new _Default();
        btnConfirm.Click += new EventHandler(def.btnConfirmBook_Click);
    }
}

The code above is a very paraphrased version of the code. But multiple buttons are generated in a loop and added to a table. The table is displayed on the Default.aspx page mentioned below. For each row in the table, the value of the CommandName property contains different values.

The aspx page I am working with is the Default page in a Web Forms .NET Web App.

I want the event triggered when one of these buttons are clicked to be carried over back into the code behind of the Default.aspx page (Default.aspx.cs).

This is what I have in the Default.aspx.cs:

public void btnConfirm_Click(object sender, EventArgs e)
{
    Button btn = sender as Button;

    DisplayConfirmation(btn.CommandName);
}

protected void DisplayConfirmation(string result)
{
    // I split result and manipulate it as necessary to get a confirmationText string

    pnlMainPanel.Visible = false; // This is where it throws NullReferenceException
    pnlConfirmationPanel.Visible = true;

    lblConfirmationText.Text = confirmationText;
}

I assume it's throwing the NullReferenceException when trying to change the visibility of the panels because I created a new instance of the _Default class so that I could set the EventHandler in the last line of the first code snippet.

But I don't know how to get this working.

Answer 1

You have assumed correct. Don't create a new instance of _Default class.

ASPX:

<form id="form1" runat="server">
<div>
    <asp:Panel ID="Panel1" runat="server">
        make me invisible;
    </asp:Panel>
</div>
</form>

Code Behind:

protected void Page_Load(object sender, EventArgs e)
{
    GenerateButtons();
}

public void GenerateButtons()
{
    AnotherClass anotherClass = new AnotherClass(this);
}

public void btnConfirmBook_Click(object sender, EventArgs e)
{
    Button btn = sender as Button;
    DisplayConfirmation();
}

protected void DisplayConfirmation()
{
    Panel1.Visible = false;
}

Another Class:

public class AnotherClass
{
    public AnotherClass(Default def)
    {

        Button btnConfirm = new Button();

        btnConfirm.Text = "Confirm";
        btnConfirm.CommandName = "Variable1,Variable2,Variable3";
        def.Form.Controls.Add(btnConfirm);

        btnConfirm.Click += new EventHandler(def.btnConfirmBook_Click);

    }
}