如何从结果集中获取特定列的值 [英] How to get the value of a particular column from a result set

问题描述

我在Visual Studio 2010中使用带有Web表单的visual basic使用asp.net 4.0代码。



我有以下代码：



表示层：

 < ％@     Page    < span class =code-attribute>标题  =    语言  =  VB    MasterPageFile   = 〜/ MasterPage.master    AutoEventWireup   =  false    CodeFile   =  Login.aspx.vb   继承  = 登录   ％> ;  
 
 <   asp：Content     ID   =  Content1    ContentPlaceHolderID   =  head    Runat   = 服务器 >  
 <   / asp：Content  >  
 <   asp：Content     ID   =  Content2    ContentPlaceHolderID   =   ContentPlaceHolder1    Runat  < span class =code-keyword> = 服务器 >  
 <   br     /  >  &l t;   br     /  >  
 <   asp：Label     ID   =  lblUsername    runat   = 服务器   正文  = 输入用户名 >  <   / asp：Label  >  
 <   asp：TextBox     ID   =  txtUsername    runat   =   server    AutoCompleteType  < span class =code-keyword> = 已停用 >  <   / asp：TextBox  >  
 <   asp：RequiredFieldValidator     ID   =  RequiredFieldValidator1    runat   =  server  
   
           ControlToValidate   =  txtUsername    ErrorMessage   =  RequiredFieldValidator  
   
           ForeColor   = 红色 >  * <   / asp：RequiredFieldValidator  >  
 <   br     /  >  < ;   br     /  < span class =code-keyword>>  
 <   asp：Label     ID   =  lblPassword    runat   =  server   文本  = 输入密码 >  <   / asp：Label  >  
 <   asp：TextBox  < span class =code-attribute>   ID   =  txtPassword    runat   =   server    TextMode   = 密码 >  <   / asp：TextBox  >  
 <   asp：RequiredFieldValidator     ID   =  RequiredFieldValidator2    runat   =  server  
   
           ControlToValidate   =  txtPassword    ErrorMessage   =  RequiredFieldValidator  
   
           ForeColor   = 红色 >  * <   / asp：RequiredFieldValidator  >  
 <   br     /  >  <   br     /  >  
选择帐户类型
 <   asp：DropDownList     ID   =  ddlAccountType    runat   =  server >  
 <   asp：ListItem    值  =  C  > 客户<   / asp ：ListItem  >  
 <   asp：ListItem    值  =  S  > 卖方<   / asp：ListItem  >  
 <   / asp：DropDownList  >  
 <   br     /  >  <   br     /  >  
 <   asp：Label     ID   =   lblRememberMe    runat  < span class =code-keyword> =  server   文本  = 记住我 >  <   / asp：标签 >  
 <   asp：CheckBox     ID   =  chkRememberMe    runat   =  server    /  >  
 <   br     /  > ;  <   br     /  >  
 <   asp：按钮    ID   =  btnLogin    runat   =  server   文字  = 登录    /  >  
 <   / asp：Content  >  

代码隐藏：

 Imports System.Data 
 Imports System.Data.SqlClient 
 Imports System.Web.Configuration 
 
 Partial Class Login 
 Inherits System.Web.UI.Page 
 Private ReadOnly _conString As String 
 
 Public Sub New（）
 _conString = 
 WebConfigurationManager.ConnectionStrings（PetiteAnnonceCS）。ConnectionString 
 End Sub 
 Protected Sub btnLogin_Click（ByVal sender As Object，ByVal e As System.EventArgs）处理btnLogin.Click 
 
 Dim con2 As New SqlConnection（_conString）
 Dim sql2 As String =SELECT UserId FROM tblUser WHERE用户名= @用户名和密码= @密码
 Dim c md2 As New SqlCommand（sql2，con2）
 cmd2.Parameters.AddWithValue（@ Username，txtUsername.Text）
 cmd2.Parameters.AddWithValue（@ Password，txtPassword.Text）
 Dim myReader As SqlDataReader 
 
使用con2 
 con2.Open（）
 myReader = cmd2.ExecuteReader 
 
如果myReader.HasRows那么
如果chkRememberMe.Checked = True则
 Session（Username）= txtUsername.Text 
 Session（LoginTime）= DateAndTime.Now.ToString 
 Session.Timeout = 50000 
如果ddlAccountType.SelectedValue =C那么
 Response.Redirect（〜/ Customer.aspx）
否则：Response.Redirect（〜/ Seller.aspx）
结束如果
 Else 
 Session（Username）= txtUsername.Text 
 Session（LoginTime）= Da teAndTime.Now.ToString 
如果ddlAccountType.SelectedValue =C那么
 Response.Redirect（〜/ Customer.aspx）
否则：Response.Redirect（〜/ Seller.aspx ）
结束如果
结束如果
 
否则
 MsgBox（登录UnSuccessful！）
结束如果
 con2.Close（） 
结束使用
 
结束次级
 
 
结束等级

我有UserId为我的表中的主键User。

当用户登录时，系统会检查用户是否有效，如果有效，则用户名存储在会话变量中。在会话中存储用户名很容易，因为我们可以轻松地从文本框中获取值，但我也想获取UserId值并将其存储在会话变量中，我对此没有任何线索。有人可以帮忙吗？

有没有办法知道用户

解决方案

 if myReader.HasRows Then 
 Session（  UserID）= reader.GetString（ 0 ）

参考：使用DataReader检索数据 [ ^ ]

你可以使用 ExecuteScalar方法 [ ^ ]因为您需要一个值。阅读文档和给出的样本。

最后我终于解决了它，但不幸的是，在我提交课程后，解决方案非常简单，我很困惑你们怎么都无法想象它出来了。

  Dim  con 作为 新 SqlConnection（_conString）
  Dim  sql 作为 字符串 =   SELECT AccountType FROM tblUser WHERE Username = @ Username 
  Dim  cmd  As  新 SqlCommand（sql，con）
 cmd.Parameters.AddWithValue（  @用户名， txtUsername.Text）
  Dim  myReader  As  SqlDataReader 
 con.Open（）
 myReader = cmd.ExecuteReader 
 DetailsView1.DataSource = myReader 
 DetailsView1.DataBind（）
 ' 从查询返回的行中读取accountType字段并将其存储在字符串中 
  Dim  AT  As   String  = myReader（  AccountType）
 如果 AT.Contains（ < span class =code-string> Customer）然后 
 Resp onse.Redirect（ 〜/ Customer.aspx）
  Else ：Response.Redirect（ 〜/ Seller.aspx） 

I'm using asp.net 4.0 code using visual basic in visual studio 2010 with web forms.

I have the following code:

Presentation layer:

<%@ Page Title="" Language="VB" MasterPageFile="~/MasterPage.master" AutoEventWireup="false" CodeFile="Login.aspx.vb" Inherits="Login" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
    <br /><br />
    <asp:Label ID="lblUsername" runat="server" Text="Enter Username"></asp:Label>
    <asp:TextBox ID="txtUsername" runat="server" AutoCompleteType="Disabled"></asp:TextBox>
    <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server"

    ControlToValidate="txtUsername" ErrorMessage="RequiredFieldValidator"

    ForeColor="Red">*</asp:RequiredFieldValidator>
    <br /><br />
    <asp:Label ID="lblPassword" runat="server" Text="Enter Password"></asp:Label>
    <asp:TextBox ID="txtPassword" runat="server" TextMode="Password"></asp:TextBox>
    <asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server"

    ControlToValidate="txtPassword" ErrorMessage="RequiredFieldValidator"

    ForeColor="Red">*</asp:RequiredFieldValidator>
    <br /><br />
    Select Account Type
    <asp:DropDownList ID="ddlAccountType" runat="server">
        <asp:ListItem Value="C">Customer</asp:ListItem>
        <asp:ListItem Value="S">Seller</asp:ListItem>
    </asp:DropDownList>
    <br /><br />
   <asp:Label ID="lblRememberMe" runat="server" Text="Remember me"></asp:Label>
   <asp:CheckBox ID="chkRememberMe" runat="server" />
   <br /><br />
    <asp:Button ID="btnLogin" runat="server" Text="Login" />
</asp:Content>

code-behind:

Imports System.Data
Imports System.Data.SqlClient
Imports System.Web.Configuration

Partial Class Login
    Inherits System.Web.UI.Page
    Private ReadOnly _conString As String

    Public Sub New()
        _conString =
        WebConfigurationManager.ConnectionStrings("PetiteAnnonceCS").ConnectionString
    End Sub
    Protected Sub btnLogin_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnLogin.Click

        Dim con2 As New SqlConnection(_conString)
        Dim sql2 As String = "SELECT UserId FROM tblUser WHERE Username=@Username And Password=@Password"
        Dim cmd2 As New SqlCommand(sql2, con2)
        cmd2.Parameters.AddWithValue("@Username", txtUsername.Text)
        cmd2.Parameters.AddWithValue("@Password", txtPassword.Text)
        Dim myReader As SqlDataReader

        Using con2
            con2.Open()
            myReader = cmd2.ExecuteReader
      
            If myReader.HasRows Then
                If chkRememberMe.Checked = True Then
                    Session("Username") = txtUsername.Text
                    Session("LoginTime") = DateAndTime.Now.ToString
                    Session.Timeout = 50000
                    If ddlAccountType.SelectedValue = "C" Then
                        Response.Redirect("~/Customer.aspx")
                    Else : Response.Redirect("~/Seller.aspx")
                    End If
                Else
                    Session("Username") = txtUsername.Text
                    Session("LoginTime") = DateAndTime.Now.ToString
                    If ddlAccountType.SelectedValue = "C" Then
                        Response.Redirect("~/Customer.aspx")
                    Else : Response.Redirect("~/Seller.aspx")
                    End If
                End If

            Else
                MsgBox("Login UnSuccessful!")
            End If
            con2.Close()
        End Using

    End Sub

   
End Class

I have the UserId as the primary key in my table User.
When the user logs in, the system checks if the user is valid, if it's valid the username is stored in a session variable. It's easy to store the username in a session because we can easily grab the value from the textbox, but I want to grab the UserId value also and store it in a session variable which I don't have any clue on how to do it. Can anyone help?
Is there a way to know the user

解决方案

If myReader.HasRows Then
   Session("UserID") = reader.GetString(0)

refer : Retrieving Data Using a DataReader[^]
you can use ExecuteScalar Method[^] since you need one value. Read the documentation and the samples given.

Finally I've finally solved it but unfortunately after I submitted my coursework, the solution is pretty straightforward, I am puzzled on how you guys could not figure it out.

Dim con As New SqlConnection(_conString)
                    Dim sql As String = "SELECT AccountType FROM tblUser WHERE Username=@Username"
                    Dim cmd As New SqlCommand(sql, con)
                    cmd.Parameters.AddWithValue("@Username", txtUsername.Text)
                    Dim myReader As SqlDataReader
                    con.Open()
                    myReader = cmd.ExecuteReader
                    DetailsView1.DataSource = myReader
                    DetailsView1.DataBind()
                    'Read the accountType field from the row returned from the                 query and store it in a string
                    Dim AT As String = myReader("AccountType")
                    If AT.Contains("Customer") Then
                        Response.Redirect("~/Customer.aspx")
                    Else : Response.Redirect("~/Seller.aspx")

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