因按鍵眾多，所以列出部分按鍵語法，其他都是重複套用就可以了。

程式碼

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace OnScreenKeyboard
{
    public partial class OnScreenKeys : Form
    {
        protected override CreateParams CreateParams
        {
            get
            {
            CreateParams param = base.CreateParams;
            param.ExStyle |= 0x08000000;
            return param;
            }
        }
        public OnScreenKeys()
        { 
        InitializeComponent();
        }

        private void buttonQ_Click(object sender, EventArgs e)
        {
            if (checkBoxCaps.Checked)
            {
                textBoxInput.Focus();
                SendKeys.Send("Q");
            }
            else
            {
                textBoxInput.Focus();
                SendKeys.Send("q");
            }
        }

        private void buttonW_Click(object sender, EventArgs e)
        {
            if (checkBoxCaps.Checked)
            {
                textBoxInput.Focus();
                SendKeys.Send("W");
            }
            else
            {
                textBoxInput.Focus();
                SendKeys.Send("w");
            }
        }

成果呈現

參考資源：

DJ Oamen How To Create On Screen Keyboard Using Sendkeys