当窗口处于最大化状态时，用户控件不调整大小 - Windows Forms C#

Question

Lately I am working on this personal app, it's form is without border so the Exit Button, Minimize Button and Maximize button, as well as the option to resize and move the form have been custom added. The app contains several User Controls which perform different functions such as Login, a Control Panel for the app and so on. The issue here is that the User Controls, which are placed within a panel ( Anchored properly, of course) in the main form are not resizing properly when the window is in a Maximized state.

To detail... the app starts at this size and while it's manually resized in minimized state the controls have no issue inheriting it's parent's (the panel) size, like this and this also works if the window is maximized while the control is visible , like this however if the window is already in a maximized state and I call the control with the designated button the control does not resize, it stays to it's minimum dimensions, like so .

At first I thought it may have something to do with the code that resizes the form so I removed everything and made the app with the default windows border and controls, basically set the border Property from none to sizable but that did nothing. Also I have tried accessing the User Control's parent (the panel) using this.Parent and then setting the width and height of the control with Width = this.Parent.Width and Height = this.Parent.Height but the parent returns null for some reason which I am yet to understand. Now, worth mentioning that those user controls are dynamically added (ie Login loginForm = new Login(); ) to the panel every time the button is clicked and then Disposed once the control is left.

I looked all over Google for this but found nothing related and at this point I am out of options. I really want the app to be resizable and must resize properly so if anyone has any solutions I am open to anything.

Thanks anticipated.

Answer 1

Meanwhile, for Winforms, I may have an answer.. the key is to use the Resize event of your user control(s), see below. I tested this in Core 3.1 and Net 4.7, you can use an default designer.cs unit with an empty form. It has no issues with resize from maximized state.

My user control for the center app is named CenteredPanel and derived from Panel. Make sure you derive your user controls from Panel and call base() on the constructor, else the docking will not work properly.

Also, your question about parenting: it was not needed to use Parent below, but if you really need it, make sure you assign it !

   public partial class Form1 : Form
    {
        private Panel panel1, panel2, panel3, panel4;
        private CenteredPanel panelApp;

        public Form1()
        {
            InitializeComponent();
            this.panel1 = new System.Windows.Forms.Panel()
              { Parent = this, Dock = DockStyle.Fill };
            this.panel2 = new System.Windows.Forms.Panel()
              { Parent = panel1, Dock = DockStyle.Left, Width = 120, BackColor = Color.FromArgb(60, 60, 60) };
            this.panel3 = new System.Windows.Forms.Panel()
              { Parent = panel1, Dock = DockStyle.Fill };
            this.panel4 = new System.Windows.Forms.Panel()
              { Parent = panel3, Dock = DockStyle.Top, Height = 60, BackColor = Color.FromArgb(60, 60, 60) };
            this.panelApp = new WindowsFormsAppCore.CenteredPanel()
              { Parent = panel3, Dock = DockStyle.Fill, BackColor = Color.FromArgb(90, 90, 90) };
            this.panel1.Controls.Add(this.panel3);
            this.panel1.Controls.Add(this.panel2);
            this.panel3.Controls.Add(this.panelApp);
            this.panel3.Controls.Add(this.panel4);
            this.Controls.Add(this.panel1);
        }
    }

    public class CenteredPanel : Panel
    {
        Label label1, label2;
        TextBox textbox1;

        public CenteredPanel() : base()
        {
            this.Resize += new System.EventHandler(this.Resizer);
            this.label1 = new System.Windows.Forms.Label()
              { Parent = this, AutoSize = true, Name = "label1", ForeColor =Color.White, Text = "Connectare Administrator" };
            this.label2 = new System.Windows.Forms.Label()
              { Parent = this, AutoSize = true, Name = "label2", ForeColor = Color.White, Text = "Nume de utilizator" };
            this.textbox1 = new System.Windows.Forms.TextBox()
              { Parent = this, AutoSize = true, Name = "textbox1", PasswordChar = '*', Text = "****" };
            this.Controls.Add(this.label1);
            this.Controls.Add(this.label2);
            this.Controls.Add(this.textbox1);
        }

        public void Resizer(object sender, EventArgs e)
        {
            Point CenteringAnchor = new Point(Width / 2, Height / 2);
            for (int i=0; i<Controls.Count; i++)
            {
                Control c = Controls[i];
                // put your resizing rules here.. this is a very simple one
                c.Location = new Point(CenteringAnchor.X - c.Width / 2, -40 + i * ((i == 1) ? 40 : 30) + CenteringAnchor.Y - c.Height / 2);
            }
        }
    }