错误:类型'System.Data.OleDb.OleDbDataReader'没有定义构造函数 [英] Error: The type 'System.Data.OleDb.OleDbDataReader' has no constructors defined

问题描述

我正在尝试使用ms访问数据库更改密码选项....​​

I am trying to change password option with ms access database....

请帮助我....

此处的代码:default.aspx.cs

here the code: 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;
    }
}

还要检查.....

编译错误说明:在执行过程中发生错误满足该请求所需的资源的汇编.请查看以下特定的错误详细信息并修改您的源适当地编码.

Compilation Error Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately.

编译器错误消息:CS0143:类型'System.Data.OleDb.OleDbDataReader'未定义构造函数

Compiler Error Message: CS0143: The type 'System.Data.OleDb.OleDbDataReader' has no constructors defined

源错误:

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

推荐答案

如错误消息所述； OleDbDataReader 没有构造函数.

As error message says; OleDbDataReader has no constructor.

来自 OleDbDataReader ;

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

To create an OleDbDataReader, you must call the ExecuteReader method of the OleDbCommand object, instead of directly using a constructor.

您可以使用 ExecuteReader 方法，该方法返回 OleDbDataReader

OleDbDataReader dr = cmd.ExecuteReader();

并且您需要在调用 ExecuteReader 方法之前添加参数值.

And you need add your parameter values before you call ExecuteReader method.

还使用 使用语句像这样处置您的 OleDbConnection ， OleDbCommand 和 OleDbDataReader ；

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())
    {
       //
    }  
}

还有史蒂夫(Steve) OleDbDataReader.Read 方法返回 boolean 值( true 为 false )，并读取您的 OleDbDataReader 结果按行.您可能需要考虑使用此方法的结果，例如 while语句.例如；

And as Steve mentioned, OleDbDataReader.Read method returns boolean value (true of false) and it reads your OleDbDataReader results row by row. You might need to consider to use the result of this method like in a while statement. For example;

while(reader.Read())
{
    //Reads your results until the last row..
}

最后，我强烈怀疑您将密码存储为纯文本.请勿这样做！使用 SHA-512哈希

As a final words, I strongly suspect you store your passwords as plain text. Don't do that! Use SHA-512 hash.

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