Auto-Resize.cs

public struct CtrlProportions {
    public float HeightProportions;
    public float WidthProportions;
    public float TopProportions;
    public float LeftProportions;
}

CtrlProportions[] ProportionsArray;

private void Form1_Load(object sender, EventArgs e) {
    Application.DoEvents();
    ProportionsArray = new CtrlProportions[Controls.Count];
    for (int I = 0; I <= Controls.Count - 1; I++) {
        ProportionsArray[I].HeightProportions = (float) Controls[I].Height / this.Height;
        ProportionsArray[I].WidthProportions = (float) Controls[I].Width / this.Width;
        ProportionsArray[I].TopProportions = (float) Controls[I].Top / this.Height;
        ProportionsArray[I].LeftProportions = (float) Controls[I].Left / this.Width;
    }
}

private void Form1_Resize(object sender, System.EventArgs e) {
    for (int I = 0; I <= Controls.Count - 1; I++) {
        Controls[I].Left = (int)(ProportionsArray[I].LeftProportions * this.Width);
        Controls[I].Top = (int)(ProportionsArray[I].TopProportions * this.Height);
        Controls[I].Width = (int)(ProportionsArray[I].WidthProportions * this.Width);
        Controls[I].Height = (int)(ProportionsArray[I].HeightProportions * this.Height);
    }
}