The visual studio cannot connect to the server.

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

namespace TestConnection 2
{
    public partial class Form 1:Form
    {
        public Form 1()
        {
            InitializeComponent();
        }

        public string contring="Server=localhost\\SQLEXPRESS; Database=master; Trusted_Connection=True";

        private void button1_Click(object sender, EventArgse)
        {
            SqlConnection con=new SqlConnection(conString);
            con.Open();
            if(con.State==System.Data.ConnectionState.Open)
            {
                string q = "insert into User(id, name) values('+textID.Text.ToString()+"', '+textName.Text.ToString()+");
                SqlCommand cmd = new SqlCommand(q,con);
                cmd.ExecuteNonQuery();
                MessageBox.Show("Connection made Successful.");
            }
        }
    }
}