Username Checker

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Windows.Forms;
using System.Net;

namespace Username_Checker
{

    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
        }
        void AboutToolStripMenuItemClick(object sender, EventArgs e)
        {
            MessageBox.Show("This program is mainly concept for how to use the ROBLOX API, created by 114k/Stiff");
        }
        void CheckbtnClick(object sender, EventArgs e)
        {
            string username = (userinput.Text);
            string output = new WebClient().DownloadString("https://www.roblox.com/UserCheck/DoesUsernameExist?username=" + username);
            if( output.Contains("true") )
            {
                label2.Text = ("Taken");
            }
            else if( output.Contains("false") )
            {
                label2.Text = ("Not Taken");
            }
        }
        void MainFormLoad(object sender, EventArgs e)
        {

        }
    }
}