VB.net&我的SQL Next-Previous-First-Last Record [英] VB.net & My SQL Next-Previous-First-Last Record

问题描述

亲爱的朋友

Sarfaraz在这里。我现在正在转向VB.net并逐渐尝试学习该语言，感谢大家对我在VB6中的早期问题的支持。



朋友我连接了我的sql服务器表与vb.net，可以显示数据网格中的所有记录。但是我在移动记录并将它们绑定到文本框时遇到问题。问题是我只能绑定最后一条记录。



我的代码正在加载文本框中的最后一条记录，但是如何转到Next-Previous-通过单击Next-Previous-First-Last Record的命令按钮并在相应的文本框中显示它们的First-Last Record。

 sql =   SELECT * FROM users 
 con.Open（）
 cmd.CommandText = sql 
 cmd.Connection = con 
 dataadapter.SelectCommand = cmd 
 datareader = cmd.ExecuteReader 
  while  datareader.Read 
 datareader.Read（）
 TextBox1.Text = datareader（  UserId）
 TextBox2.Text = datareader（ 用户名）
 TextBox3.Text = datareader（ 年龄）
 结束 当 
 
 con.Close（ ）
 

请帮助

谢谢

解决方

您还没有任何约束。



你却放的记录，一个内容在时间到文本框中。对于您迭代过的每条记录，您将文本框的内容替换为最新记录的内容。



尝试阅读BindingNavigator [ ^ ]并且可能会看 this [ ^ ]。

亲爱的所有

我尝试并最终想出解决方案。

代码如下： -

 进口 MySql .Data.MySqlClient 
 
 公共 类 Form1 
  Dim  con  As  MySqlConnection = 新 MySqlConnection（  data source = localhost; database = students; user id = root; password = root）
 < span class =code-keyword> Dim  ds  As  DataSet = 新 DataSet 
  Dim  dataadapter 作为 新 MySqlDataAdapter（  从用户中选择*，con）
  Dim  cmd 作为 MySqlCommand = 新 MySqlCommand（）
  Dim  dv 正如 DataView 
  Dim  cm  As  CurrencyManager 
  Dim  datareader  As  MySqlDataReader 
 
  Public   Sub  filldatasetandview（）
 ds = 新 DataSet 
 dataadapter.Fill（ds ，  users）
 dv = 新 DataView（ds.Tables（  users））
 cm = < span class =code-keyword> CType （ Me  .BindingContext（dv），CurrencyManager）
 结束  Sub  
 公共  Sub  bindfields（）
 TextBox1.DataBindings.Clear（）
 TextBox2.DataBindings.Clear（）
 TextBox3.DataBindings.Clear（）
 TextBox1.DataBindings.Add（   text，dv，  userid ）
 TextBox2.DataBindings.Add（  text，dv，   username）
 TextBox3.DataBindings.Add（  text，dv， 年龄）
 结束  Sub  
 公共  Sub  showposition（）
 TextBox4.Text = cm.Position +  1 &  &   of&  & cm.Count（）
 
 结束  Sub  
 
 私有  Sub  Form1_Load（ ByVal  sender < span class =code-keyword> As  System。 Object ， ByVal  e  As  System.EventArgs）句柄  MyBase  .Load 
 filldatasetandview（）
 bindfields（）
 showposition（）
 结束  Sub  
 
 私有  Sub  previousrecord_Click（ ByVal  sender  As  System。 Object ， ByVal  e  As  System.EventArgs） Handles  previousrecord.Click 
 cm.Position = cm.Position  -   1  
 showposition（）
 结束  Sub  
 
 私有  Sub  nextrecord_Click（ ByVal  sender  As  System。 Object ， ByVal  e  As  System.EventArgs） Handles  nextrecord.Click 
 cm .Position = cm.Position +  1  
 showposition（）
 结束  Sub  
 
 私有  Sub  lastrecord_Click（ ByVal  sender  As  System。 Object ， ByVal  e  As  System.EventArgs） Handles  lastrecord。点击
 cm.Position = cm.Count  -   1  
 showposition（）
 结束  Sub  
 
 私有  Sub  firstrecord_Click（ ByVal  sender  As  System。对象， ByVal  e 作为 System.EventArgs）句柄 firstrecord.Click 
 cm.Position =  0  
 showposition（）
 电子nd   Sub  
 结束 类 

Dear friends
Sarfaraz here. I am now moving to VB.net and gradually trying to learn the language thanks to you all for support on my earlier questions in VB6.

Friends I have connected My sql server table with vb.net and could display all the records in a datagrid. But I have a problem in moving the records and bind them to text boxes. The problem is that i could only bind the last record.

My code is is working to load last record in the text boxes but how to move to Next-Previous-First-Last Record by clicking on command buttons for Next-Previous-First-Last Record and display them in text boxes accordingly.

sql = "SELECT * FROM users"
          con.Open()
          cmd.CommandText = sql
          cmd.Connection = con
          dataadapter.SelectCommand = cmd
          datareader = cmd.ExecuteReader
          While datareader.Read
              datareader.Read()
              TextBox1.Text = datareader("UserId")
              TextBox2.Text = datareader("Username")
              TextBox3.Text = datareader("Age")
          End While

          con.Close()

Please help
Thank you

解决方案

You haven't bound anything.

All you did was put the contents of the records, one at time into the textbox. With each record you iteracted over, you replaced the contents of the textboxes with the contents of the latest record.

Try reading up on BindingNavigator[^] and maybe watch this[^].

Dear all
I try and finally come up with the solutions.
The code is as under:-

Imports MySql.Data.MySqlClient

Public Class Form1
    Dim con As MySqlConnection = New MySqlConnection("data source=localhost;database=students;user id=root;password=root")
    Dim ds As DataSet = New DataSet
    Dim dataadapter As New MySqlDataAdapter("select * from users", con)
    Dim cmd As MySqlCommand = New MySqlCommand()
    Dim dv As DataView
    Dim cm As CurrencyManager
    Dim datareader As MySqlDataReader

    Public Sub filldatasetandview()
        ds = New DataSet
        dataadapter.Fill(ds, "users")
        dv = New DataView(ds.Tables("users"))
        cm = CType(Me.BindingContext(dv), CurrencyManager)
    End Sub
    Public Sub bindfields()
        TextBox1.DataBindings.Clear()
        TextBox2.DataBindings.Clear()
        TextBox3.DataBindings.Clear()
        TextBox1.DataBindings.Add("text", dv, "userid")
        TextBox2.DataBindings.Add("text", dv, "username")
        TextBox3.DataBindings.Add("text", dv, "age")
    End Sub
    Public Sub showposition()
        TextBox4.Text = cm.Position + 1 & "     " & "of" & "    " & cm.Count()

    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        filldatasetandview()
        bindfields()
        showposition()
    End Sub

    Private Sub previousrecord_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles previousrecord.Click
        cm.Position = cm.Position - 1
        showposition()
    End Sub

    Private Sub nextrecord_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles nextrecord.Click
        cm.Position = cm.Position + 1
        showposition()
    End Sub

    Private Sub lastrecord_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lastrecord.Click
        cm.Position = cm.Count - 1
        showposition()
    End Sub

    Private Sub firstrecord_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles firstrecord.Click
        cm.Position = 0
        showposition()
    End Sub
End Class

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