ASP.NET - VB.NET - 从 MS-Access 数据库中检索记录

Question

我正在尝试从 MS-Access 数据库中检索记录数据并将其存储到变量中。

我正在使用这个 SQL 命令来查询数据库：

Dim cmdRead As OleDbCommand = New OleDbCommand("SELECT UserID FROM [User] where Username=?", conn)

如何在 VB.NET 中从 UserID 列（在 db 中）读取数据并将其存储到 VB.NET 中的变量中？

我基本上想要做的是检索用户 ID，以便我可以从同一个表中检索用户的姓名和姓氏。

注意：我将 ASP.NET 与 Web Develop 2003 和 MS-Access 2003 db 一起使用。

这是完整的代码：

  Imports System.Data.OleDb

Partial Class _Default
    Inherits System.Web.UI.Page

    Protected Sub btnLogin_Click(sender As Object, e As System.EventArgs) Handles btnLogin.Click

        Dim conn As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Users\Brian\Documents\Visual Studio 2010\WebSites\WebSite3\db.mdb;")


        Dim cmd As OleDbCommand = New OleDbCommand("SELECT Username, Password FROM [User] where Username=? and Password=?", conn)

        cmd.Parameters.AddWithValue("@Username", txtUsername.Text)
        cmd.Parameters.AddWithValue("@Password", txtPassword.Text)


        Try
            conn.Open()
            Dim read As OleDbDataReader = cmd.ExecuteReader()
            If read.HasRows Then
                While read.Read()
                    If txtUsername.Text = read.Item("username").ToString And txtPassword.Text = read.Item("password").ToString Then

                        Dim tID As Long = read.Item("UserID").ToString
                        Dim tName As String = read.Item("CustomerName").ToString
                        Dim tSurname As String = read.Item("CustomerSurname").ToString

                        lblLogged.Text = lblLogged.Text + tName + tSurname

                        lblLogged.Visible = True
                    End If
                End While
            Else
                lblLogged.Text = "Login unsuccessful"
            End If

            read.Close()
        Catch ex As Exception
            Response.Write(ex.Message())

        Finally
            conn.Close()
        End Try


    End Sub

End Class

Answer 1

这应该放在你的 Try 块中

conn.Open()             
Dim read As OleDbDataReader = cmd.ExecuteReader()             
If read.HasRows Then              
    While read.Read()             
        If txtUsername.Text = read.Item("username").ToString And txtPassword.Text = read.Item("password").ToString Then                
            Dim tID as long = read.Item("UserID").ToString
        Else                 
            lblLogged.Text = "Login unsuccessful"             
        End If   
    End While           
End If   

在 finally 块中

read.Close()

Answer 2

在您的示例中出现了问题。请试试这个。

首先更改 OleDbCommand 以检索用户 ID，当您从同一个表中读取时不需要第二个命令，我认为 UserName 和 Password 标识一个唯一用户

Dim cmd As OleDbCommand = New OleDbCommand("SELECT UserID, Username, Password FROM [User] where Username=? and Password=?", conn) 

然后添加你的参数并查询数据库

Try             
     conn.Open()
     Dim read As OleDbDataReader = cmd.ExecuteReader()             
     If read.HasRows Then              
         read.Read()
         ' Now you can read the Item and pass the values to your textboxes             
         txtUsername.Text = read.Item("username").ToString 
         txtPassword.Text = read.Item("password").ToString 
         txtUserID.Text = read.Item("userid").ToString  
     Else                 
          lblLogged.Text = "Login unsuccessful"             
     End If              
     read.Close()         
Catch ex As Exception             
     Response.Write(ex.Message())          
Finally             
     conn.Close()         
 End Try