用dataAdapter.update更新DataGridView中的数据,代码总是抛出异常System.NullReferenceException:“未将对象引用设置到对象的实例。” dataAdapter 是 null,该怎么修改?
这里是详细代码
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 System.Data.SqlClient;
namespace 项目二
{
public partial class Form1 : Form
{
SqlDataAdapter dataAdapter;
DataSet dataSet;
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
string connString = "Data Source = (local);Initial Catalog = Mybookshop;User ID = sa;pwd = 123456";
SqlConnection con = new SqlConnection(connString);
string sql = "SELECT * FROM book1";
SqlDataAdapter dataAdapter = new SqlDataAdapter(sql, con);
DataSet dataSet;
dataSet = new DataSet();
dataAdapter.Fill(dataSet, "Mydata");
dataGridView1.DataSource = dataSet.Tables[0];
}
private void button2_Click(object sender, EventArgs e)
{
SqlCommandBuilder builder = new SqlCommandBuilder(dataAdapter);
dataAdapter.Update(dataSet, "Mydata");
}
}
}
输入数据点击更新后错误显示为