Auto resize to fill all multi panels

Question

How to size all panels as fill in form1 window without changing panels size? I searched on Google. very difficult to find. That why i want to help. like in below Thanks.

If 3 panels this will be resized:

4 Panels:

5 Panels:

9 Panels:

Answer 1

You can use a FlowLayoutPanel. Insert in your form and set Dock=Fill in the designer. Add this const to your form:

private const int PanelSize = 200;

In the constructor:

this.flowLayoutPanel1.Resize += this.OnFlowLayoutPanel1_Resize;
this.OnFlowLayoutPanel1_Resize(this.flowLayoutPanel1, EventArgs.Empty);

And use this method to create/destroy the panels:

private void OnFlowLayoutPanel1_Resize(object sender, EventArgs e)
{
    // At least, one panel
    var columns = Math.Max(1, this.flowLayoutPanel1.Width / (double)PanelSize);
    var rows = Math.Max(1, this.flowLayoutPanel1.Height / (double)PanelSize);

    var panelsCount = this.flowLayoutPanel1.Controls.Count;
    var requiredPanelsCount = rows * columns;
    var diff = requiredPanelsCount - panelsCount;
    if (diff > 0)
    {
        // We need more panels: create it
        for (int i = 0; i < diff; i++)
        {
            var panel = new Panel
            {
                Size = new Size(PanelSize, PanelSize),
                TabIndex = this.flowLayoutPanel1.Controls.Count, 
                BackColor = GetBackColor()
            };
            this.flowLayoutPanel1.Controls.Add(panel);
        }
    }
    else
    {
        // Remove unneeded panels
        for (int i = 0; i < diff; i++)
        {
            this.flowLayoutPanel1.Controls.RemoveAt(
                this.flowLayoutPanel1.Controls.Count - 1);
        }
    }
}

I have used this method to set a color:

private Color GetBackColor()
{
    var colors = new[] 
    { 
        Color.Black, Color.Red, Color.Green, Color.Blue, Color.White
    };
    var index = this.flowLayoutPanel1.Controls.Count % colors.Length;
    return colors[index];
}

Adapt it to your needs.

If you need fill entire form, you must work with a variable PanelSize. Use a minimum and maximum size for the panels instead a fixed value.

I'm creating/removing Panels to fill entire space. If you only need fixed panels in the form, you don't need the resize event. The FlowLayoutControl do what you need.