C#窗体程序学生管理

代码如下：

public static string constr = "Data Source=FUSHUAI;Initial Catalog=product;Integrated Security=True";

public static SqlConnection con = new SqlConnection(constr);
private void Form1_Load(object sender, EventArgs e)
{
    gettable();
}

//执行查询操作
public static DataTable query(string sql)
{
    SqlDataAdapter sda = new SqlDataAdapter(sql, constr);
    DataTable dtable = new DataTable();
    sda.Fill(dtable);
    return dtable;

}
//执行更新操作
public static string update(string sql)
{
    try
    {
        SqlConnection conn = new SqlConnection("Data Source=.;Initial Catalog=数据表;Integrated Security=True");  // 打开数据库连接
        conn.Open();
        SqlCommand cmd = new SqlCommand(sql, conn);
        int result = cmd.ExecuteNonQuery();
        conn.Close();
        return "success";
    }
    catch (Exception e)
    {
        MessageBox.Show(e.Message);
        return e.ToString();
    }

}
// 添加按钮
private void button1_Click(object sender, EventArgs e)
{
    string id = textBox1.Text.Trim();  // 学号
    string name = textBox2.Text.Trim();// 名称
    string gender = comboBox1.Text.Trim();// 性别
    string age = textBox3.Text.Trim();// 年龄

    string intosql = $"insert into [Students] values('{id}','{name}','{gender}','{age}')";
    update(intosql);
    MessageBox.Show("添加成功");
    gettable();
}

public void gettable()
{
    string sql = "select * from students";
    dataGridView1.DataSource = query(sql);
}
// 删除按钮
private void button2_Click(object sender, EventArgs e)
{
    string id = dataGridView1.SelectedRows[0].Cells[0].Value.ToString();  // 学号
    string intosql = $"delete from [Students] where Studentid='{id}'";
    update(intosql);
    MessageBox.Show("删除成功");
    gettable();
}