Question

我正在尝试使用ms access database更改密码选项....

请帮助我们......

这里的代码： default.aspx.cs

protected void Button1_Click(object sender, EventArgs e)
{
    try
    {

        OleDbConnection myCon = new OleDbConnection(ConfigurationManager.ConnectionStrings["vhgroupconnection"].ConnectionString);
        myCon.Open();

        string userid = txtuserid.Text;
        string oldpass = txtoldpass.Text;
        string newPass = txtnewpass.Text;
        string conPass = txtconfirmpass.Text;

        string q = "select user_id,passwd from register where user_id = @userid and       passwd = @oldpass";

        OleDbCommand cmd = new OleDbCommand(q, myCon);

        OleDbDataReader reader = new OleDbDataReader();



        cmd.Parameters.AddWithValue("@userid", txtuserid.Text);

        cmd.Parameters.AddWithValue("@oldpass", txtoldpass.Text);



        reader = cmd.ExecuteReader();
        reader.Read();

        if (reader["user_id"].ToString() != String.Empty && reader["passwd"].ToString() != String.Empty)
        {
            if (newPass.Trim() != conPass.Trim())
            {
                lblmsg.Text = "New Password and old password does not match";

            }
            else
            {
                q = "UPDATE register SET passwd = @newPass WHERE user_id =@userid";
                cmd = new OleDbCommand(q, myCon);
                cmd.Parameters.AddWithValue("@newPasss", txtnewpass.Text);
                cmd.Parameters.AddWithValue("@userod", txtuserid.Text);
                cmd.Parameters.AddWithValue("@passwd", txtoldpass.Text);

                int count = cmd.ExecuteNonQuery();

                if (count > 0)
                {
                    lblmsg.Text = "Password changed successfully";
                }
                else
                {
                    lblmsg.Text = "password not changed";
                }
            }
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }
}

也请检查.....

编译错误说明：期间发生错误   编译服务此请求所需的资源。请   查看以下特定错误详细信息并修改您的来源   代码恰当。

编译器错误消息：CS0143：类型   ＆＃39; System.Data.OleDb.OleDbDataReader＆＃39;没有定义构造函数

来源错误：

Line 36:             OleDbCommand cmd = new OleDbCommand(q, myCon);
Line 37: 
Line 38:             OleDbDataReader reader = new OleDbDataReader();
Line 39:             
Line 40:

Answer 1

正如错误消息所说; OleDbDataReader没有构造函数。

来自documentation of OleDbDataReader;

要创建OleDbDataReader，您必须调用ExecuteReader方法 OleDbCommand对象，而不是直接使用构造函数。

您可以使用返回OleDbDataReader

的ExecuteReader方法

OleDbDataReader dr = cmd.ExecuteReader();

您需要在之前添加参数值，然后调用ExecuteReader方法。

还可以使用using statement来处理您的OleDbConnection，OleDbCommand和OleDbDataReader之类的内容;

using(OleDbConnection myCon = new OleDbConnection(conString)) using(OleDbCommand cmd = myCon.CreateCommand()) { //Define your sql query and add your parameter values. using(OleDbDataReader dr = cmd.ExecuteReader()) { // } }

正如史蒂夫mentioned，OleDbDataReader.Read method返回boolean值（true的{{1}}），它会显示您的false结果逐行。您可能需要考虑在 while语句中使用此方法的结果。例如;

OleDbDataReader

最后，我强烈怀疑您将密码存储为纯文本。 不要这样做！使用SHA-512 hash。

Answer 2

正如MSDN明确指出的那样，To create an OleDbDataReader, you must call the ExecuteReader method of the OleDbCommand object, instead of directly using a constructor.

您无法使用new实例化它，这就是您正在做的事情，这就是您收到错误的原因。删除有问题的行并将其更改为此以消除错误：

OleDbDataReader reader = cmd.ExecuteReader();

另外，请记住使用using块来确保资源得到妥善处理。

using(OleDbConnection myCon = new OleDbConnection(ConfigurationManager.ConnectionStrings["vhgroupconnection"].ConnectionString))
{
 OleDbCommand cmd = new OleDbCommand(q, myCon);

 //Add parameters etc

OleDbDataReader reader = cmd.ExecuteReader();

//Rest of the processing
}

Answer 3

问题：您尝试通过调用OleDbDataReader制作new OleDbDataReader()的新实例，而应使用OleDbCommand.ExecuteReader()创建一个阅读器。

在以下代码中，请注意使用using语句（这应该确保OleDbDataReader的情况下连接关闭或读取器关闭。）

protected void Button1_Click(object sender, EventArgs e)
{
    try
    {
        string sConnString = ConfigurationManager.ConnectionStrings["vhgroupconnection"].ConnectionString;
        using(OleDbConnection myCon = new OleDbConnection(sConnString))
        {
             myCon.Open();
             string userid = txtuserid.Text;
             string oldpass = txtoldpass.Text;
             string newPass = txtnewpass.Text;
             string conPass = txtconfirmpass.Text;

             string q = "select user_id,passwd from register where user_id = @userid and passwd = @oldpass";

             OleDbCommand cmd = new OleDbCommand(q, myCon);
             cmd.Parameters.AddWithValue("@userid", txtuserid.Text);
             cmd.Parameters.AddWithValue("@oldpass", txtoldpass.Text);

             string sUserId = string.Empty;
             string sPass = string.Empty;

             using(OleDbDataReader reader = cmd.ExecuteReader())
             {
                if(reader.Read()) //assumption: one record returned
                {           
                   sUserId = reader["user_id"].ToString();
                   sPass = reader["passwd"].ToString();

                }
             }

             if (sUserId != string.Empty && sPass != string.Empty)
             {
               if (newPass.Trim() != conPass.Trim())                   
                   lblmsg.Text = "New Password and old password does not match";
               else
               {
                    q = "UPDATE register SET passwd = @newPass WHERE user_id =@userid";
                    cmd = new OleDbCommand(q, myCon);
                    cmd.Parameters.AddWithValue("@newPass", txtnewpass.Text);
                    cmd.Parameters.AddWithValue("@userid", txtuserid.Text);                       

                    int count = cmd.ExecuteNonQuery();

                    if (count > 0)                
                       lblmsg.Text = "Password changed successfully";                
                    else                
                       lblmsg.Text = "password not changed";

               }
            }
        }
    }
    catch (Exception ex)
      {
        throw ex;
      }
}

错误：类型＆＃39; System.Data.OleDb.OleDbDataReader＆＃39;没有定义构造函数

3 个答案: