Question

我正在编写一个C＃窗体，所以当你点击退出时，它会关闭
窗口，当您单击登录时，它会检查登录信息并将您带到另一种形式，如果它是正确的。当我点击登录时，我收到一个错误，上面写着，
System.Data.dll中发生了类型为“System.Data.SqlClient.SqlException”的未处理异常。它会抛出sda.Fill（dt）;

这一行的错误

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 LoginForm
{
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }


    private void button2_Click(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\v11.0;AttachDbFilename=C:\Users\carme\Documents\Data.mdf;Integrated Security=True;Connect Timeout=30;");
        SqlDataAdapter sda = new SqlDataAdapter("Select Count(*) from Login where Username'" + textBox1.Text + "' and Password = '" + textBox2.Text + "'", con);
        DataTable dt = new DataTable();
        sda.Fill(dt);

        if (dt.Rows[0][0].ToString() == "1")
        {
            this.Hide();
            Main ss = new Main();
            ss.Show();
        }
        else
        {
            MessageBox.Show("Check your username and password");
        }
    }

    private void button1_Click(object sender, EventArgs e)
    {
        this.Close();
    }
}
}

Answer 1

也许你应该改变

SqlDataAdapter sda = new SqlDataAdapter("Select Count(*) from Login where Username'" + textBox1.Text + "' and Password = '" + textBox2.Text + "'", con);

到

SqlDataAdapter sda = new SqlDataAdapter("Select Count(*) from Login where Username ='" + textBox1.Text + "' and Password = '" + textBox2.Text + "'", con);

Answer 2

您需要打开您的连接，然后您应该使用using语句，因为SqlConnection和SqlDataAdaptor实现IDisposable并且应该关闭。 using语句将为您解决这个问题。

还使用参数来防止SQL注入。

你也忘了用户名后的'='。

    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 LoginForm
    {
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }


            private void button2_Click(object sender, EventArgs e)
            {


                using (SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\v11.0;AttachDbFilename=C:\Users\carme\Documents\Data.mdf;Integrated Security=True;Connect Timeout=30;"))
                {
                    con.Open();
                    using (SqlDataAdapter sda = new SqlDataAdapter("Select Count(*) from Login where Username = @userName and Password = @passWord, con))
                    {
                       sda.SelectCommand.Parameters.AddWithValue("@userName", textBox1.Text);
                       sda.SelectCommand.Parameters.AddWithValue("@passWord", textBox2.Text);
                        DataTable dt = new DataTable();
                        sda.Fill(dt);

                        if (dt.Rows[0][0].ToString() == "1")
                        {
                            this.Hide();
                            Main ss = new Main();
                            ss.Show();
                        }
                        else
                        {
                            MessageBox.Show("Check your username and password");
                        }
                    }
                }

            }

            private void button1_Click(object sender, EventArgs e)
            {
                this.Close();
            }

    }
    }

我没有测试过，但看起来它对我来说是对的。

System.Data.dll中发生未处理的“System.Data.SqlClient.SqlException”类型异常

2 个答案: