Question

For my C# Windows Form Application, I have created a flowlayoutpanel that contains several panels. Inside the panel, I have a button “Clear” for each and every single panel.

How do I write the event handler for the code for the button “Clear” such that once I have click the button, the panel would sort of be “Removed” from the flowlayoutpanel.

This is a short part of the code of the adding of panels to the flowlayoutpanel.

        nFlowPanel.Controls.Add(createNotificationPanel());
        nFlowPanel.Controls.Add(createNotificationPanel());
        nFlowPanel.Controls.Add(createNotificationPanel());
        nFlowPanel.Controls.Add(createNotificationPanelImpt());
        nFlowPanel.Controls.Add(createNotificationPanelImpt());

and this is the code for the button “Clear”

Button btnClear = new Button
        {
            Text = "Clear",
            Name = "btnClear",
            Location = new Point(416, 17)
        };
        p.Controls.Add(btnClear);
        btnClear.Click += new EventHandler(buttonClear_Click);

So what should i write in the following method to have the effect of removing e.g. the second panel that was added in the first part of code I have written?

void buttonClear_Click(object sender, EventArgs e)
    {
        throw new NotImplementedException();
    }

EDIT

the code for creating my panel is

var p = new Panel 
        {
             BorderStyle = BorderStyle.FixedSingle , 
             Size = new Size(506,100),
             Name = "notifyPanel"
        };

and the code for creating my FlowLayoutPanel is

var nFlowPanel = new FlowLayoutPanel
        {
            FlowDirection = FlowDirection.TopDown,
            WrapContents = false,
            AutoScroll = true,
            Size = new Size(530, 377),
            Location = new Point(13, 145)
        };

and the code for my button clear is

void buttonClear_Click(object sender, EventArgs e)
    {
        var button = (Control)sender;
        var panel = button.Parent.Controls["notifyPanel"];
        panel.Dispose();
    }

however it gives the error
Object reference not set to an instance of an object.
on the panel.Dispose() line.

anyone can help?

Answer 1

The Controls.Remove() method is very dangerous, it doesn’t dispose the control. Which will live on, moved to the so-called parking window, using up both Windows and managed resources. After a bit less than 10,000 times doing this it crashes your program when Windows is no longer willing to let you create any more windows.

Call the control’s Dispose() method instead. That also automatically removes the control from its container.

void buttonClear_Click(object sender, EventArgs e)
{
    var panel = nFlowPanel.Controls["notifyPanel"];
    panel.Dispose();
}