Imports System.Data
Imports System.Data.OleDb
Imports System.Data.SqlClient Public Class Form1
Dim conn As New OleDbConnection
Dim comm As OleDbCommand
Dim dataset As DataSet
Dim dataad As OleDbDataAdapter
Dim id As Integer Private Sub Form1_Leave(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Leave
conn.Close()
comm.Dispose()
dataset.Dispose()
dataad.Dispose() End Sub Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
conn.ConnectionString = "provider=microsoft.jet.oledb.4.0;data source=../../data.mdb"
conn.Open()
comm = New OleDbCommand
comm.CommandText = "Select ID,用户名 , 密码 From [user]"
dataset = New DataSet
dataad = New OleDbDataAdapter(comm.CommandText, conn)
dataad.Fill(dataset, "user")
dataview.DataSource = dataset.Tables("user")
'下面是给变量id赋值，即取数据库中记录的总数
id = setid()
conn.Close()
comm.Dispose()
username.Text = ""
userpassw.Text = ""
End Sub
Function setid() As Integer
Dim i As Integer
Dim dr As OleDbDataReader
comm.CommandText = "select count(*) as 总数 from [user]"
comm.Connection = conn
dr = comm.ExecuteReader()
dr.Read()
i = dr.Item("总数")
setid = i + 1
dr.Close()
End Function Private Sub adddata_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles adddata.Click
If username.Text = "" Or userpassw.Text = "" Then
MsgBox("用户名或密码不能为空！", 64)
Else
Dim Connstring2 As String = "provider=microsoft.jet.oledb.4.0; data source=../../data.mdb"
Dim cn As New OleDb.OleDbConnection(Connstring2)
cn.Open()
Dim cmd As New OleDb.OleDbCommand
cmd.Connection = cn
cmd.CommandType = CommandType.Text
cmd.CommandText = "INSERT INTO [user] (ID,用户名,密码) VALUES (" & id & ",'" & Me.username.Text & "','" & Me.userpassw.Text & "') "
cmd.ExecuteNonQuery() '执行sql语句并返回受影响的行数
MsgBox("成功添加一条记录", 64)
cn.Close()
id += 1
username.Text = ""
userpassw.Text = ""
conn.Close()
Button1.PerformClick()
End If End Sub Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
dataview.ReadOnly = False
dataview.DataSource = Nothing
dataset.Tables("user").Rows.Clear() '清空dataset里面的user表
dataad.Fill(dataset, "user") '填充dataset
dataview.DataSource = dataset.Tables("user") '将dataset中的user表映射到datagridview中

dataview.ReadOnly = True
username.Text = ""
userpassw.Text = ""
End Sub Private Sub select__Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles select_.Click
selectdata(username.Text)
username.Text = ""
userpassw.Text = "" End Sub
Function selectdata(ByVal usern As String) '查询记录的过程
If username.Text = "" Then
MsgBox("请输入用户名！", 64)
Else
Dim dr As OleDbDataReader
Dim chars1 As String
Dim chars2 As String
conn.Open()
comm.Connection = conn
comm.CommandType = CommandType.Text
comm.CommandText = "select 用户名,密码 from [user] where 用户名='" & username.Text & "'"
dr = comm.ExecuteReader()
If dr.Read() Then
chars1 = dr.Item("用户名")
chars2 = dr.Item("密码")
MsgBox("用户名为：" + chars1 + "；" + "密码为" + chars2, 64)
Else
MsgBox("未查询到任何记录！", 48)
End If
conn.Close()
End If End Function Private Sub delete__Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles delete_.Click
If username.Text = "" Then
MsgBox("请输入用户名！", 64)
Else Dim i As Integer
i = MsgBox("您确定要删除这条记录吗？", 49)
If i = 1 Then
deletedata(username.Text)
End If
username.Text = ""
userpassw.Text = ""
End If End Sub
Function deletedata(ByVal usern As String) '删除记录的过程
Dim i As Integer = 0
conn.Open()
comm.Connection = conn
comm.CommandType = CommandType.Text
comm.CommandText = "delete [user] from [user] where 用户名='" & username.Text & "'"
i = comm.ExecuteNonQuery()
If i > 0 Then
MsgBox("成功删除一条记录！", 64)
Else
MsgBox("删除时出错！", 16)
End If
conn.Close()
comm.Dispose()
Button1.PerformClick() End Function
Private Sub save_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) End Sub
End Class

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