这是完整代码

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;
using System.Collections;
using System.Configuration;

namespace WindowsFormsApplication1
{
public partial class f1 : Form
{
public f1()
{
InitializeComponent();
}
string connStr = ConfigurationManager.ConnectionStrings["str"].ConnectionString;
private void Form1_Load(object sender, EventArgs e)
{

}

private void button1_Click(object sender, EventArgs e)
{
string sql = "select id,ios,kfyy,qdkf,javascript,android,PHP,sjk,NET from Table_2";
SqlConnection conn = new SqlConnection(connStr);
SqlCommand cmd = new SqlCommand(sql, conn);
DataTable dt = new DataTable();
SqlDataAdapter sda = new SqlDataAdapter(cmd);
sda.Fill(dt);
dgv1.DataSource = dt;
}

private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
{
//获取字段名为ios的单元格内容

tb1.Text = dgv1.Rows[e.RowIndex].Cells[e.ColumnIndex].Value.ToString();
tb2.Text = dgv1.Rows[e.RowIndex].Cells["ID"].Value.ToString();

}

private void button3_Click(object sender, EventArgs e)
{



string sql = "delete from Table_2 where 1=0";
if (tb1.Text.Trim() == "")
{
MessageBox.Show("无标签可删！");
return;
}
else if (dgv1.CurrentRow.Selected)
{
sql = sql + "and ID=" + Convert.ToInt32(dgv1.CurrentRow.Cells[0].Value.ToString());
}

int n = 0;
SqlConnection conn = new SqlConnection(connStr);
SqlCommand cmd = new SqlCommand(sql, conn);
conn.Open();
n = cmd.ExecuteNonQuery();
if (n == 0)
{
MessageBox.Show("不存在的标签！");
return;
}
else if (n > 0)
{
MessageBox.Show("删除成功！");
}
conn.Close();
//删除完后刷新当前数据
Refresh();
}

private void tb1_TextChanged(object sender, EventArgs e)
{

}

private void tb2_TextChanged(object sender, EventArgs e)
{

}

private void button2_Click(object sender, EventArgs e)
{
//定义一个初始值n=0，用于判断后期是否成功插入数据
int n = 0;
string sql = "insert into Table_2(ios)values (@ios)";
//判断插入数据是否为空，如果为空，则提示重新插入
if (tb1.Text.Trim() == "")
{
MessageBox.Show("插入数据不能为空，请重新插入！");
return;

}
//向数据库插入参数
SqlParameter[] param = {
new SqlParameter("@ios",tb1.Text),
};
SqlConnection conn = new SqlConnection(connStr);
SqlCommand cmd = new SqlCommand(sql, conn);
conn.Open();
cmd.Parameters.AddRange(param);
n = cmd.ExecuteNonQuery();
if (n == 0)
{
MessageBox.Show("添加失败！");
return;
}
else if (n > 0)
{
MessageBox.Show("添加成功");
}
conn.Close();
//调用refresh方法，在添加完成数据后，自动刷新，显示新数据
Refresh(true);
}

private void button4_Click(object sender, EventArgs e)
{
//在对数据进行修改前，对文本框的内容做一下检查，如果为空，则提示重新输入
if (tb1.Text.Trim() == "")
{
MessageBox.Show("文本框内容不能为空！");
return;
}
//使用SQL update更新语句
//获取文本框中输入的内容，通过ID进行更新（ID为当前鼠标点击行的ID）
string sqlUpdate = "update Table_2 set conn ='" + tb1.Text +
"'where conn='" + dgv1.ToString() + "'";
SqlConnection conn = new SqlConnection(connStr);
SqlCommand cmdUpdate = new SqlCommand(sqlUpdate, conn);
conn.Open();
int n = cmdUpdate.ExecuteNonQuery();
// if (n == 0)
// {
//提示失败
// MessageBox.Show("更新失败！");
// return;
// }
// else if (n > 0)
// {
//更新成功
MessageBox.Show("更新成功！");
// }
//完成更新后，关闭数据库，释放资源空间
conn.Close();
//刷新
Refresh();
}
public void Refresh(bool isAdded = false)
{
string sql = "select ios from Table_2";
SqlConnection conn = new SqlConnection(connStr);
SqlCommand cmd = new SqlCommand(sql, conn);
DataTable dt = new DataTable();
SqlDataAdapter sda = new SqlDataAdapter(cmd);
sda.Fill(dt);
dgv1.DataSource = dt;

if (isAdded)
{
if (dt.Rows.Count > 0) dgv1.Rows[0].Selected = false;
dgv1.Rows[dt.Rows.Count - 1].Selected = true;
}
}

private void tb2_TextChanged_1(object sender, EventArgs e)
{

}

}
}