Flowlayoutpanel control in a child form can not be modified

Question

when the father form has a flowlayoutpanel control, child form can not modify its any attribute though the modifiers of flowlayoutpanel is public. But other controls of father form like button can be modified in child form.

Answer 1

I test the method that provide in the SO thread, and it works fine. Here is a workaround you can refer to.
We can replace the FlowLayoutPanel with a custom FlowLayoutPanel class.

Parent.Designer.cs:

  partial class Form1
{
    // Code omitted
    // …
        private void InitializeComponent()
        {
            flowLayoutPanel1 = new FlowLayoutPanelHeritable();
            this.SuspendLayout();
            // 
            // flowLayoutPanel1
            // 
            flowLayoutPanel1.Location = new System.Drawing.Point(24, 12);
            flowLayoutPanel1.Name = "flowLayoutPanel1";
            flowLayoutPanel1.Size = new System.Drawing.Size(285, 174);
            flowLayoutPanel1.TabIndex = 0;
            // Code omitted
            // …
        }

        // declare a custom FlowLayoutPanel
        public FlowLayoutPanelHeritable flowLayoutPanel1;
        public System.Windows.Forms.Button button1;
    }

    // Custom FlowLayoutPanel inherited from FlowLaypitPanel
    [Designer(typeof(ParentControlDesigner))]
    public class FlowLayoutPanelHeritable : FlowLayoutPanel
    {
    }

Hope this can help you.

Answer 2

What is the “child form” you mentioned? A form opened from “father form” by clicking a button? Or an MDI child form?
If is the former, I tested it and it works fine. The following is the test demo.

Parent Form:

  public FlowLayoutPanel FLP  
    {  
        get { return flowLayoutPanel1; }  
        set { flowLayoutPanel1 = value; }  
    }  
  
    private void btOpenChild_Click(object sender, EventArgs e)  
    {  
        Form2 form = new Form2();  
        form.Show();  
}  
  

Child Form:

 private void btModifyPanel_Click(object sender, EventArgs e)  
    {  
        Form1 form1 = (Form1)Application.OpenForms["Form1"];  
        form1.FLP.BackColor = Color.Red;  
}  

If is an MDI child form, please provide some related code to reproduce the issue.