using System;

using System.Windows.Forms;

using System.Runtime.InteropServices;

​

namespace WindowsFormsApp

{

    public partial class Form1 : Form

    {

        [DllImport("user32")]

        private static extern bool HideCaret(IntPtr hWnd);

​

        public Form1()

        {

            InitializeComponent();

            textBox1.GotFocus += textBox1_GotFocus;

        }

​

        private void textBox1_GotFocus(object sender, EventArgs e)

        {

            HideCaret(textBox1.Handle);

        }

    }

}