C#操作数据库

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;


namespace wlw_database
{
    public partial class Form1 : Form
    {
        SqlConnection MyConnect = new SqlConnection ();
    
        public Form1()
        {
            InitializeComponent();
        }


        private void OpenDatabase_Click(object sender, EventArgs e)
        {
            MyConnect.ConnectionString = "Data Source=(local); Initial Catalog=物联网; User ID= gly; Password=123456";
            MyConnect.Open();
            MessageBox.Show("打开数据库成功");
        }


        private void CloseDatabase_Click(object sender, EventArgs e)
        {
            MyConnect.Close();
            MessageBox.Show("关闭数据库成功");
        }


        private void CreateTable_Click(object sender, EventArgs e)
        {
            SqlCommand CreateTableCmd = new SqlCommand();
            CreateTableCmd.Connection = MyConnect;
            CreateTableCmd.CommandType = CommandType.Text;
            CreateTableCmd.CommandText = "CREATE TABLE Student(Stu_ID nchar(8) not null Primary Key,Name nvarchar(20) not null,Sex nchar(2) not null,Adress nvarchar(50) not null,Class_Code nchar(4))";
//            CreateTableCmd.ExecuteScalar();


            CreateTableCmd.CommandText = "CREATE TABLE Teacher(Teacher_ID nchar(8) not null Primary Key,Name nvarchar(20) not null,phone nchar(20) not null,Subject nchar(20) not null,Commot nchar(200) not null)";
//            CreateTableCmd.ExecuteScalar();


            CreateTableCmd.CommandText = "CREATE TABLE Subject(ID nchar(8) not null Primary Key,Subject nvarchar(20) not null,Start_Lesson nchar(40) not null)";
//            CreateTableCmd.ExecuteScalar();


            CreateTableCmd.CommandText = "CREATE TABLE Grade(ID nchar(8) not null Primary Key,Name nvarchar(8) not null,Subject nvarchar(20) not null,Grade nchar(40) not null)";
//            CreateTableCmd.ExecuteScalar();


            CreateTableCmd.CommandText = "CREATE TABLE Addrbook(Name nvarchar(8) not null,Phone nvarchar(20) not null,qq nchar(12) not null,Address nchar(40) not null)";
            CreateTableCmd.ExecuteScalar();
            MessageBox.Show("创建表成功");
        }


        private void DropTable_Click(object sender, EventArgs e)
        {
            SqlCommand CreateTableCmd = new SqlCommand();
            CreateTableCmd.Connection = MyConnect;
            CreateTableCmd.CommandType = CommandType.Text;
            CreateTableCmd.CommandText = "Drop TABLE student";
            CreateTableCmd.ExecuteScalar();
            MessageBox.Show("删除表成功");
        }
    }
}