Finisar.SQLite.SQLiteException打印数据到sqlite数据库

我正在制作一款涉及用户的游戏，我在运行时得到了一个Finisar.SQLite.SQLiteException。这是代码:

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;
using Finisar.SQLite;
namespace Racing_Manager
{
public partial class SaveNameBox : Form
{
    public string command;
    public string savedName;
    public string firstName;
    public string savedTeamName;
    public string surname;
    public SQLiteConnection sql_con;
    public SQLiteCommand sql_cmd;
    public SQLiteDataReader DB;
    public void setConnection()
    {
        sql_con = new SQLiteConnection("Data Source=database.sqlite;Version=3;New=False;Compress=True;");
    }
    public static SaveNameBox create = new SaveNameBox();
    public SaveNameBox()
    {
        InitializeComponent();
    }
    //Save Name
    private void TextBoxSaveName_TextChanged(object sender, EventArgs e)
    {
        savedName = TextBoxSaveName.Text;
    }
    //Team Name
    private void teamName_TextChanged(object sender, EventArgs e)
    {
        savedTeamName = teamName.Text;
    }
    //First Name
    private void textBoxFirstName_TextChanged(object sender, EventArgs e)
    {
        firstName = textBoxFirstName.Text;
    }
    //Surname
    private void textBoxSurname_TextChanged(object sender, EventArgs e)
    {
        surname = textBoxSurname.Text;
    }
    //Confirmation
    private void confirm_Click(object sender, EventArgs e)
    {
        command = String.Format("INSERT INTO Users VALUES ({0},{1},{2},{3})", savedName, firstName, surname, savedTeamName);
        ExecuteQuery(command);
    }

    public void ExecuteQuery(string command)
    {
        setConnection();
        sql_con.Open();
        sql_cmd.CommandText = command;
    }
}
}

异常在这一行:sql_con.Open ();我该如何解决这个问题?非常感谢您的帮助