C# Windows Forms Calling a Grandchild Form inside a panel in the Grandparent form from the Parent Form

Question

I have 3 forms, Main, product and details. In the main form I have a side menu and a panel called pnlContent. In this menu I have a button that fills the pnlContent with the product form. Inside the product form I have another button that fills the pnlContent with the form Details but does not display. They could help me?

(Main form)Call to the product form:

    private void btnProduto_Click(object sender, EventArgs e)
    {
        frmProduto frm = new frmProduto
        {
            TopLevel = false,
            AutoScroll = true,
            FormBorderStyle = FormBorderStyle.None,
            Dock = DockStyle.Fill
        };

        this.pnlContent.Controls.Clear();
        this.pnlContent.Controls.Add(frm);
        frm.Show();
    }

(Form Product)Call to form details:

    private void btnDetalhes_Click(object sender, EventArgs e)
    {          
        frmDetalhes Detalhes = new frmDetalhes
        {
            TopLevel = false,
            AutoScroll = true,
            FormBorderStyle = FormBorderStyle.None,
            Dock = DockStyle.Fill
        };

        frmPrincipal Principal = new frmPrincipal();
        Principal.pnlContent.Controls.Clear();
        Principal.pnlContent.Refresh();
        Principal.pnlContent.Controls.Add(Detalhes);

        Detalhes.Show();
        Principal.Refresh();   
        Principal.pnlContent.Refresh();
        this.Close();
    }

Answer 1

Instead of instantiating frmPrincipal again, you can access it through Parent and locate the control panel.

var Principal = this.ParentForm;
var pnlContentPrincipal = Principal.Controls.Find("pnlContent", true).FirstOrDefault(); 
    pnlContentPrincipal.Controls.Clear();
    pnlContentPrincipal.Refresh();
    pnlContentPrincipal.Controls.Add(Detalhes);

    Detalhes.Show();

    Principal.Refresh();
    pnlContentPrincipal.Refresh();
    this.Close();