用C#连接数据库，实现对学生模块的增删改查

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

namespace text3_CRUD
{
    public partial class Form1 : Form
    {
        //把连接数据库的字符串提取出来，就不用每次都要写，增加代码复用性
        private string str = "data source=本地IP;initial catalog=数据库名;user ID=用户名;pwd=密码";

        public Form1()
        {
            InitializeComponent();
   
        }
       
        private void TextBox5_TextChanged(object sender, EventArgs e)
        {

        }

        private void Form1_Load(object sender, EventArgs e)
        {


        }

        private void Label10_Click(object sender, EventArgs e)
        {

        }

        /// 

        /// 添加学生信息档案
        /// 
        /// 
        /// 
        private void ButAdd_Click(object sender, EventArgs e)
        {
            //获取各个文本框的数据
            string name = txtname.Text;
            string sex = txtsex.Text;
            string college = txtcollege.Text;
            string id = txtid.Text;
            string grade = txtgrade.Text;
            string phone = txtphone.Text;
            string email = txtemail.Text;
            string qq = txtqq.Text;
            string room = txtroom.Text;

            using (var conn = new SqlConnection(this.str))//定义一个数据库连接实例
            {
                conn.Open();//打开数据库
                
                Form1 f = new Form1();//实例化Form1窗体对象

                if (f.Existence(id, conn))//检查数据库 存不存在此条记录，存在则插入
                {
                    SqlParameter[] para = new SqlParameter[]//构建存储过程的输入参数
                    {
                        new SqlParameter("@name",name),
                        new SqlParameter("@sex", sex),
                        new SqlParameter("@college", college),
                        new SqlParameter("@id", id),
                        new SqlParameter("@grade", grade),
                        new SqlParameter("@phone", phone),
                        new SqlParameter("@email", email),
                        new SqlParameter("@qq", qq),
                        new SqlParameter("@room", room),

                    };

                    string sql = "insert into Students values(@name, @sex, @college, @id, @grade, @phone, @email, @qq, @room);";//定义一个数据库操作指令集

                    SqlCommand com = new SqlCommand(sql, conn);//执行数据库操作指令

                    com.Parameters.AddRange(para);//將参数和命令对象的参数集合绑定
                    int result = (int)com.ExecuteNonQuery();//针对Connection执行的SQL语句，返回受影响的行数，result > 0则表示SQL语句执行成功
                    if (result > 0)
                    {
                        MessageBox.Show("添加成功！");//弹窗显示“添加成功” 
                        this.Form1_Load_1(null, null);//刷新数据
                        
                    }
                    else
                    {
                        MessageBox.Show("添加失败！");
                    }
                    
                }
                else
                {
                    MessageBox.Show("数据已经存在！");
                }
                conn.Close();//关闭数据库
                //Application.Exit();//关闭整个应用程序

            }
        }

        /// 

        /// 根据ID值判断数据表Students中是否存在这个人，存在返回false，不存在返回true
        /// 
        /// 
        /// 
        /// 
        public bool Existence(string id, SqlConnection conn)
        {
            string txtStr = string.Format( "select id from Students where id = '{0}' " ,id);//定义一个数据库操作指令集
            SqlDataAdapter sda = new SqlDataAdapter(txtStr, conn);//定义一个数据库适配器
            DataSet ds = new DataSet();//定义数据集合
            sda.Fill(ds);//填充数据集合
            DataTable dt = ds.Tables[0];//將数据集合中的第一张表赋值给DataTable
            if(dt.Rows.Count > 0)   //count > 0表示有数据
            {
                return false;
            }
            else
            {
                return true;
            }
            
        }
        /// 

        /// 对数据库进行的动态查询，不管用户掌握的信息有多少都可以查询
        /// 
        /// 
        /// 
        private void BtnSelect_Click(object sender, EventArgs e)
        {
            //获取各个文本框的数据
            string name = txtname.Text;
            string sex = txtsex.Text;
            string college = txtcollege.Text;
            string id = txtid.Text;
            string grade = txtgrade.Text;
            string phone = txtphone.Text;
            string email = txtemail.Text;
            string qq = txtqq.Text;
            string room = txtroom.Text;

            using(var conn = new SqlConnection(this.str))//定义一个数据库连接实例
            {
                conn.Open();//打开数据库
                StringBuilder sb = new StringBuilder();//创建一个字符串变量
                sb.Append("select name, sex, college, id, grade,phone, email, qq, room from Students where 1=1");
                //判断用户有没有给出其它的查询条件，有则添加进sql语句
                if (name != "")
                {
                    sb.AppendFormat(" and name = '{0}'", name);
                }
                if (sex != "")
                {
                    sb.AppendFormat(" and sex = '{0}'", sex);
                }
                if (college != "")
                {
                    sb.AppendFormat(" and college = '{0}'", college);
                }
                if (id != "")
                {
                    sb.AppendFormat(" and id = '{0}'", id);
                }
                if (grade != "")
                {
                    sb.AppendFormat(" and grade = '{0}'", grade);
                }
                if (phone != "")
                {
                    sb.AppendFormat(" and phone = '{0}'", phone);
                }
                if (email != "")
                {
                    sb.AppendFormat(" and email = '{0}'", email);
                }
                if (qq != "")
                {
                    sb.AppendFormat(" and qq = '{0}'", qq);
                }
                if (room != "")
                {
                    sb.AppendFormat(" and room = '{0}'", room);
                }
                string sql = sb.ToString();
                SqlDataAdapter adapter = new SqlDataAdapter(sql, conn);
                DataSet ds = new DataSet();//定义一个数据集合
                adapter.Fill(ds);//填充数据集合
                dataGridView1.DataSource = ds.Tables[0];//把数据集合绑定到dataGridView上，dataGridView会以表格的形式显示出来
                conn.Close();//关闭数据库

            }
        }
        /// 

        /// 修改学生信息
        /// 
        /// 
        /// 
        private void BtnUpdate_Click(object sender, EventArgs e)
        {
            //获取各个文本框的数据
            string name = txtname.Text;
            string sex = txtsex.Text;
            string college = txtcollege.Text;
            string id = txtid.Text;
            string grade = txtgrade.Text;
            string phone = txtphone.Text;
            string email = txtemail.Text;
            string qq = txtqq.Text;
            string room = txtroom.Text;

            //构建存储过程的输入参数
            SqlParameter[] para = new SqlParameter[]
            {
                new SqlParameter("@name",name),
                new SqlParameter("@sex", sex),
                new SqlParameter("@college", college),
                new SqlParameter("@id", id),
                new SqlParameter("@grade", grade),
                new SqlParameter("@phone", phone),
                new SqlParameter("@email", email),
                new SqlParameter("@qq", qq),
                new SqlParameter("@room", room)
            };
            using(var conn = new SqlConnection(this.str))
            {
                conn.Open();//打开数据库；
                string sql = "update Students set name = @name, sex = @sex, college = @college, id = @id, grade = @grade, phone = @phone, email = @email, qq = @qq, room = @room where id = @id";
                SqlCommand com = new SqlCommand(sql, conn);//执行数据库操作指令
                com.Parameters.AddRange(para);//将参数和命令对象的参数集合绑定
                int result = (int)com.ExecuteNonQuery();//查询返回的第一行第一列
                if(result > 0)
                {
                    MessageBox.Show("修改成功！");
                    this.Form1_Load_1(null, null);//修改完数据后，重新刷新属性Form1窗口，以查看变化的内容
                    conn.Close();//关闭数据库
                }
            }


            //SqlDataAdapter sda = new SqlDataAdapter();
        }
        /// 

        /// 刷新DataGridView里的数据
        /// 
        /// 
        /// 
        private void Form1_Load_1(object sender, EventArgs e)
        {
            
            using (var conn = new SqlConnection(this.str))//定义一个数据库连接实例
            {
                conn.Open();//打开数据库
                string sql = "select * from Students";//定义一个数据库操作指令
                SqlDataAdapter sda = new SqlDataAdapter(sql, conn);//定义数据库适配器
                DataSet ds = new DataSet();//定义数据集合
                sda.Fill(ds);//填充数据集合
                dataGridView1.DataSource = ds.Tables[0];
                conn.Close();//关闭数据库
            }
        }

        private void DataGridView1_CellClick(object sender, DataGridViewCellEventArgs e)
        {
            
        }
        /// 

        /// 选中DataGridView的行，这一行的数据返回到对应的文本框
        /// 
        /// 
        /// 
        private void DataGridView1_CellClick_1(object sender, DataGridViewCellEventArgs e)
        {   
            //SelectedRows[0] 获取用户选定行的集合(选中的第一行就是0，一次类推)
            //Cells["name"] 获取用于填充行的单元格集合(就是列) .Value就是它的值,最后ToString转字符串
            txtname.Text = dataGridView1.SelectedRows[0].Cells["name"].Value.ToString();
            txtsex.Text = dataGridView1.SelectedRows[0].Cells["sex"].Value.ToString();
            txtcollege.Text = dataGridView1.SelectedRows[0].Cells["college"].Value.ToString();
            txtid.Text = dataGridView1.SelectedRows[0].Cells["id"].Value.ToString();
            txtgrade.Text = dataGridView1.SelectedRows[0].Cells["grade"].Value.ToString();
            txtphone.Text = dataGridView1.SelectedRows[0].Cells["phone"].Value.ToString();
            txtemail.Text = dataGridView1.SelectedRows[0].Cells["email"].Value.ToString();
            txtqq.Text = dataGridView1.SelectedRows[0].Cells["qq"].Value.ToString();
            txtroom.Text = dataGridView1.SelectedRows[0].Cells["room"].Value.ToString();
 
        }
        /// 

        /// 删除某个学生的所有数据
        /// 
        /// 
        /// 
        private void BtnDelete_Click(object sender, EventArgs e)
        {
            using(var conn = new SqlConnection(this.str))//创建一个数据库连接实例
            {
                conn.Open();//连接数据库
                string sql = string.Format("delete from Students where id = '{0}'", txtid.Text);//往数据库操作指令中传值
                //如果传的值不是很多的话，就用这种方法；如果有很多就用SqlParameter[]

                SqlCommand com = new SqlCommand(sql, conn);//执行数据库删除指令

                int result = (int)com.ExecuteNonQuery();//返回结果，result > 0则为修改成功
                if(result > 0)
                {
                    MessageBox.Show("删除成功！");
                    this.Form1_Load_1(null, null);//刷新数据
                    conn.Close();//关闭数据库
                }
            }
        }
        /// 

        /// 对文本框进行清空处理，方便重新输入下一个学生信息
        /// 
        /// 
        /// 
        private void BtnClear_Click(object sender, EventArgs e)
        {
            txtname.Text = null;
            txtsex.Text = null;
            txtcollege.Text = null;
            txtid.Text = null;
            txtgrade.Text = null;
            txtphone.Text = null;
            txtemail.Text = null;
            txtqq.Text = null;
            txtroom.Text = null;
        }
    }
}

Students表