有一段关于C#的代码怎样用它连接我的SQL数据库呢?这段代码连接数据库的部分在哪呢？

using System;
using System.Collections.Generic;
using
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;


namespace 停车场管理收费系统
{
    public partial class 系统主界面 : Form
    {
        public 系统主界面()
        {
            InitializeComponent();
        }

        private void toolStripButton1_Click(object sender, EventArgs e)
        {
            费用设置界面 form = new 费用设置界面();
            form.Show();
            form.MdiParent = this;
        }

        private void toolStripButton2_Click(object sender, EventArgs e)
        {
            修改管理员密码界面 form = new 修改管理员密码界面();
            form.Show();
            form.MdiParent = this;
        }

        private void tsbConnect_Click(object sender, EventArgs e)
        {
            if (IC.State||IC.UserConnect()>0)
            {
                tsslTCInfo.Text = "已连接！";
            }
            else
            {
                tsslTCInfo.Text = "连接失败，请检查端口！";
            }
        }

        private void tsbBreak_Click(object sender, EventArgs e)
        {
            IC.UserBreak();
            tsslTCInfo.Text = "已断开连接！";
        }

        private void 系统主界面_Load(object sender, EventArgs e)
        {

        }

        private void toolStripButton3_Click(object sender, EventArgs e)
        {
            会员开户界面 form = new 会员开户界面();
            form.Show();
            form.MdiParent = this;
        }

        private void toolStripButton4_Click(object sender, EventArgs e)
        {
            会员缴费界面 form = new 会员缴费界面();
            form.Show();
            form.MdiParent = this;
        }

        private void toolStripButton5_Click(object sender, EventArgs e)
        {
            会员注销界面 form = new 会员注销界面();
            form.Show();
            form.MdiParent = this;
        }

        private void toolStripButton6_Click(object sender, EventArgs e)
        {
            会员查询界面 form = new 会员查询界面();
            form.Show();
            form.MdiParent = this;
        }

        private void toolStripButton7_Click(object sender, EventArgs e)
        {
            车辆入库界面 form = new 车辆入库界面();
            form.Show();
            form.MdiParent = this;
        }

        private void toolStripButton8_Click(object sender, EventArgs e)
        {
            出库缴费界面 form = new 出库缴费界面();
            form.Show();
            form.MdiParent = this;
        }

        private void toolStripButton11_Click(object sender, EventArgs e)
        {
            DialogResult result = MessageBox.Show("确定退出系统吗？", "系统提示", MessageBoxButtons.YesNo , MessageBoxIcon.Question);
            if (result == DialogResult.Yes)
            {
                this.Close();
            }
           
        }

        private void 系统主界面_FormClosing(object sender, FormClosingEventArgs e)
        {
           
            

        }

        private void 费用设置ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            费用设置界面 form = new 费用设置界面();
            form.Show();
            form.MdiParent = this;
        }

        private void 修改密码UToolStripMenuItem_Click(object sender, EventArgs e)
        {
            修改管理员密码界面 form = new 修改管理员密码界面();
            form.Show();
            form.MdiParent = this;
        }

        private void 开户OToolStripMenuItem_Click(object sender, EventArgs e)
        {
            会员开户界面 form = new 会员开户界面();
            form.Show();
            form.MdiParent = this;
        }

        private void 充值RToolStripMenuItem_Click(object sender, EventArgs e)
        {

            会员缴费界面 form = new 会员缴费界面();
            form.Show();
            form.MdiParent = this;
        }

        private void 注销CToolStripMenuItem_Click(object sender, EventArgs e)
        {
            会员注销界面 form = new 会员注销界面();
            form.Show();
            form.MdiParent = this;
        }

        private void 查询QToolStripMenuItem_Click(object sender, EventArgs e)
        {
            会员查询界面 form = new 会员查询界面();
            form.Show();
            form.MdiParent = this;
        }

        private void 入库ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            车辆入库界面 form = new 车辆入库界面();
            form.Show();
            form.MdiParent = this;
        }

        private void 出库ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            出库缴费界面 form = new 出库缴费界面();
            form.Show();
            form.MdiParent = this;
        }

        private void 退出XToolStripMenuItem_Click(object sender, EventArgs e)
        {
            DialogResult result = MessageBox.Show("确定退出系统吗？", "系统提示", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
            if (result == DialogResult.Yes)
            {
                this.Close();
            }
        }

    }
}