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  • vb.net亚博优惠活动之随机文件的读写操作

  • 2015-01-18 15:12 来源:未知
随机文件的读写操作(相关vb.net亚博优惠活动)
随机文件的打开也用fileopen完成,只是打开随机文件的形式为:openmode.random
和二进制文件的操作一样,读随机文件用的是fileget方法,写入随机文件用的是fileput方法。
应用实例:将一批个人记录存放到随机文件中。[实验报告41 ]
见,随机文件的读写个人记录的存取,程序为:
Public Class Form1
??? Structure person
??????? Dim name As String
??????? Dim age As Integer
??????? Dim sex As String
??????? Dim note As String
??? End Structure
??? Dim filename As String = "d:\p.txt"
??? Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
??????? Dim fn As Integer
??????? Dim p As person
??????? fn = FreeFile()
??????? FileOpen(fn, filename, OpenMode.Random)
??????? p.name = "黄子昱" : p.age = 15 : p.sex = "男"
??????? p.note = "中学生" : FilePut(fn, p)
??????? p.name = "李立立" : p.age = 10 : p.sex = "男"
??????? p.note = "小学生" : FilePut(fn, p)
??????? p.name = "王安石" : p.age = 5 : p.sex = "男"
??????? p.note = "儿 童" : FilePut(fn, p)
??????? FileClose()
??? End Sub
?
??? Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
??????? Dim fn As Integer
??????? Dim p As person
??????? Dim s As String = ""
??????? fn = FreeFile()
??????? FileOpen(fn, filename, OpenMode.Random)
??????? Do While Not EOF(fn)
??????????? FileGet(fn, p)
??????????? s = s + p.name + "? " + p.sex + "? " + Str(p.age) + "? " + p.note + vbCrLf
??????? Loop
??????? FileClose()
??????? TextBox1.Text = s
??? End Sub
?
??? Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
??????? End
??? End Sub
End Class
说明:
记录对文件的读写操作是整体进行的(即不分域,而是整个记录读、写),但要给记录赋值,却要就记录的每个域分别进行的。
综合实例:设计一个人员记录录入窗口,可以完成记录的增加、删除、保存操作。同时还可以进行记录的前后浏览:第一条记录,下一条,前一条,最后一条记录。程序见,人员记录的录入与浏览--文件操作综合。[实验报告42]
此时在当前目录下就生成一个数据文件:
L:\vb.net\人员记录的录入与浏览--文件操作综合\人员记录的录入与浏览--文件操作综合\bin\Debug\person.dat
程序为:
Imports System.IO
Public Class Form1
??? Structure personstruct
??????? Dim name, sex, tel As String
??????? Dim age As Integer
??? End Structure
??? Dim datafile As String
??? Dim person() As personstruct
??? Dim curp As Integer
??? Private Sub readdata()
??????? '从文件中读取记录数据到数组person中
??????? Dim n, fn As Integer
??????? Dim ps As New personstruct
??????? fn = FreeFile()
??????? FileOpen(fn, datafile, OpenMode.Random)
??????? n = 0
??????? Do While Not EOF(fn)
??????????? FileGet(fn, ps)
??????????? ReDim Preserve person(n)
??????????? person(n) = ps
??????????? n = n + 1
??????? Loop
??????? FileClose(fn)
??? End Sub
??? Private Sub savedata()
??????? '把数组person中的数据保存到文件中
??????? Dim n, fn As Integer
??????? If File.Exists(datafile) Then File.Delete(datafile)
??????? If IsNothing(person) Then Exit Sub
??????? fn = FreeFile()
??????? FileOpen(fn, datafile, OpenMode.Random)
??????? For n = 0 To UBound(person)
??????????? FilePut(fn, person(n))
??????? Next
??????? FileClose(fn)
??? End Sub
??? Private Sub getdata()
??????? '将数组中记录显示在窗口中
??????? Dim flag As Boolean = False
??????? If Not IsNothing(person) Then
??????????? If (curp >= 0 And curp <= UBound(person)) Then
??????????????? Textname.Text = person(curp).name
??????????????? Textage.Text = Trim(Str(person(curp).age))
??????????????? Texttel.Text = person(curp).tel
??????????????? male.Checked = IIf(person(curp).sex = "男", True, False)
??????????????? female.Checked = IIf(person(curp).sex = "男", False, True)
??????????????? flag = True
??????????????? gbdata.Visible = True
??????????????? lbpos.Text = "当前记录:" + Str(curp + 1) + "/" + Str(UBound(person) + 1)
??????????? End If
??????? End If
??????? If flag = False Then
??????????? gbdata.Visible = False
??????????? lbpos.Text = ""
??????? End If
??? End Sub
??? Private Sub putdata()
??????? '把当前控件中的数据保存到数组person中
??????? If Not IsNothing(person) Then
??????????? If (curp >= 0 And curp <= UBound(person)) Then
??????????????? person(curp).name = Textname.Text
??????????????? person(curp).sex = IIf(male.Checked, "男", "女")
??????????????? person(curp).age = Val(Textage.Text)
??????????????? person(curp).tel = Texttel.Text
??????????? End If
??????? End If
??? End Sub
?
??? Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
??????? '程序关闭时保存各个记录数据
??????? savedata()
??? End Sub
?
??? Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
??????? '程序启动时确定数据文件datafile在当前目录中
??????? datafile = Application.StartupPath
??????? If Microsoft.VisualBasic.Right(datafile, 1) <> "\" Then
?? ?????????datafile = datafile + "\"
??????? End If
??????? datafile = datafile + "person.dat"
??????? '读文件数据
??????? readdata()
??????? '显示记录
??????? curp = 0
??????? getdata()
??? End Sub
?
??? Private Sub add_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles add.Click
??????? '增加记录
??????? Dim n As Integer
??????? If IsNothing(person) Then
??????????? n = 0
??????? Else
??????????? n = UBound(person) + 1
??????? End If
??????? ReDim Preserve person(n)
??????? person(n).name = ""
??? ????person(n).sex = "男"
??????? person(n).age = 0
??????? person(n).tel = ""
??????? '显示新增加的空记录
??????? curp = n
??????? getdata()
??? End Sub
?
??? Private Sub save_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles save.Click
????? ??'保存数据到person数组中
??????? putdata()
??? End Sub
?
??? Private Sub first_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles first.Click
??????? '转到第一条记录
??????? If Not IsNothing(person) Then
??????????? curp = 0
??????????? getdata()
??????? End If
??? End Sub
?
??? Private Sub prior_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles prior.Click
??????? '转到前一条记录
??????? If Not IsNothing(person) Then
??????????? If curp > 0 Then curp = curp - 1
??????????? getdata()
??????? End If
??? End Sub
?
??? Private Sub thenext_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles thenext.Click
??????? '转到下一条记录
??????? If Not IsNothing(person) Then
??????????? If curp < UBound(person) Then curp = curp + 1
? ??????????getdata()
??????? End If
??? End Sub
?
??? Private Sub last_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles last.Click
??????? '转到最后一条记录
??????? If Not IsNothing(person) Then
??????????? curp = UBound(person)
??????????? getdata()
??????? End If
??? End Sub
?
??? Private Sub delete_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles delete.Click
??????? '删除当前记录
??????? Dim i, n As Integer
??????? Dim ps As New personstruct
??????? If Not IsNothing(person) Then
??????????? If MsgBox("确定要删除该记录?", MsgBoxStyle.YesNo Or MsgBoxStyle.Question, "删除") = MsgBoxResult.Yes Then
??????????????? n = UBound(person)
??????????????? '把curp+1,purp+2...,n记录向前移动
??????????????? For i = curp + 1 To n
??????????????????? person(i - 1) = person(i)
??????????????? Next
??????????????? n = n - 1
??????????????? If n >= 0 Then
??????????????????? '调整person数组,删除它的最后一个元素
??????????????????? ReDim Preserve person(n)
??????????????????? If curp = n + 1 Then curp = n
??????????????? Else
??????????????????? '记录删除完毕
??????????????????? person = Nothing
??????????????????? curp = -1
??????????????? End If
??????????????? '显示新的记录
??????????????? getdata()
??????????? End If
??????? End If
??? End Sub
End Class
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