c# - 在创建密码更改表单时出现异常

Question

我正在创建密码更改表单。当我执行表单并填写文本框时，它给出一个异常消息 There already and open DataReader associated with this command which must be closed first.

他是我正在使用的代码:

private bool CompareStrings(string string1, string string2)
        {
            return String.Compare(string1, string2, true, System.Globalization.CultureInfo.InvariantCulture) == 0 ? true : false;
        }

    private void button1_Click(object sender, EventArgs e)
    {
        try
        {
            SqlConnection con1 = new SqlConnection();
            con1.ConnectionString = "data source=.;Initial catalog=inventory;Integrated Security=true";
            con1.Open();

            SqlCommand cmd = new SqlCommand("SELECT ISNULL(username, '') AS username, ISNULL(password,'') AS password FROM login WHERE username='" + textBox1.Text + "' and password='" + textBox2.Text + "'", con1);

            SqlDataReader dr = cmd.ExecuteReader();

            string userText = textBox1.Text;
            string passText = textBox2.Text;

            while (dr.Read())
            {
                if (this.CompareStrings(dr["username"].ToString(), userText) &&
                    this.CompareStrings(dr["password"].ToString(), passText))
                {
                    SqlCommand cmd2 = new SqlCommand("UPDATE login SET password='" + textBox3.Text + "'where username='" + textBox1.Text + "'", con1);
                    cmd2.ExecuteNonQuery();
                    MessageBox.Show("Password Changed Successfully");
                }
                else
                {
                    MessageBox.Show("Incorrect Old password");                        
                }

            }

            dr.Close();

            con1.Close();

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }

Answer 1

您不能在 SqlDataReader 时执行命令在同一连接上打开。您可以执行以下两项操作之一来更改您的代码:

1. 创建第二个连接并在第二个连接上运行更新查询。

2. 存储阅读器的数据，关闭阅读器，稍后更新所有数据。在您的情况下，您可以存储所有用户名以使用 Username in (<yourlisthere>) 在一个更新查询中更新和更新它们