如图  有多个控件 根据上下左右键 控制每个控件的焦点；

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        //定义一个二位数组  存放TextBox控件
        TextBox[,] arr;

        private void Form1_Load(object sender, EventArgs e)
        {
            //初始化数组
            arr = new TextBox[3, 3]{{textBox1,textBox2,textBox3},
               {textBox4,textBox5,textBox6},
               {textBox7,textBox8,textBox9}
            };

        }

        /// <summary>
        /// 窗体键盘事件   注： 启用此事件之前 先设置KeyPreView属性为True
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Form1_KeyDown(object sender, KeyEventArgs e)
        {
            //首先获取当前焦点的控件
            TextBox txt = (TextBox)GetFocusedControl();

            //获取当前焦点控件的在数组中对应的位置  此值事先存放在控件的Tag属性中
            int x = int.Parse(txt.Tag.ToString().Substring(0, 1));
            int y = int.Parse(txt.Tag.ToString().Substring(1, 1));

            if (e.KeyCode == Keys.Left)
            {
                if (y > 0)
                {
                    arr[x, y-1].Focus();
                }
            }
            else if (e.KeyCode == Keys.Right)
            {
                if (y < 2)
                {
                    arr[x,y + 1].Focus();
                }
            }
            else if (e.KeyCode == Keys.Up)
            {
                if (x > 0)
                {
                    arr[x-1, y].Focus();
                }
            }
            else if (e.KeyCode == Keys.Down)
            {
                if (x < 2)
                {
                    arr[x+1, y].Focus();
                }
            }
        }

        // DLL调用注册
        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.Winapi)]
        private static extern IntPtr GetFocus();
        /// <summary>
        /// 当前拥有焦点的控件
        /// </summary>
        /// <param name="formControl"></param>
        /// <returns></returns>
        public static Control GetFocusedControl()
        {
            Control focusedControl = null;
            try
            {
                IntPtr focusedHandle = GetFocus();

                if (focusedHandle != IntPtr.Zero)
                {
                    focusedControl = Control.FromChildHandle(focusedHandle);
                }
            }
            catch { }

            return focusedControl;
        }
    }

C# Winform 自适应大小 按上下键切换控件焦点（转）

按上下键切换控件焦点（只对textbox有效）

private void textBox2_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyValue == 40 || e.KeyValue == 13)
            {
                SendKeys.Send("{TAB}");
            }
            if (e.KeyValue == 38)
            {
               int index= this.textBox2.TabIndex;
                for (int i = 0; i < this.Controls.Count; i++)
                {
                    if (this.Controls[i].TabIndex == (index - 1))
                    {
                        this.Controls[i].Focus();
                        break;
                    }
                }
            }
        }

自适应大小

private void Form1_SizeChanged(object sender, EventArgs e)
        {
           
            if (this.WindowState.ToString() == "Maximized")
            {
                this.dataGridView1.Width = this.Size.Width-35;
            }
            else if (this.WindowState.ToString() == "Normal")
            {
                this.dataGridView1.Width = this.Size.Width-35;
            }
            else
            {
                this.dataGridView1.Width = this.Size.Width-35;
            }          
        }