private void richTextBox1_TextChanged(object sender, EventArgs e)
{
    Process process = new Process();
    process.StartInfo.FileName = "cmd.exe";
    process.StartInfo.CreateNoWindow = true;
    process.StartInfo.RedirectStandardInput = true;
    process.StartInfo.RedirectStandardOutput = true;
    process.StartInfo.UseShellExecute = false;
    process.Start();
    process.StandardInput.WriteLine("ipconfig");
    process.StandardInput.Flush();
    process.StandardInput.Close();
    process.WaitForExit();

    string s = process.StandardOutput.ReadToEnd();

    richTextBox1.Text = s;
}