[英]VB.Net populating text boxes from text file
我正在创建一个库存管理系统,其中数据存储在文本文件中。 我可以将数据保存到文本文件中,但是在跟踪器屏幕上它应该显示当前库存,例如:制造商、处理器、视频、表单、RAM 等。但是,我所有的文本框都保持空白,我没有肯定为什么。 它没有正确阅读或更新文本。
跟踪器.vb
Private Sub txtManufacturer_TextChanged(sender As Object, e As EventArgs) Handles txtManufacturer.TextChanged
Dim objMyStreamReader = System.IO.File.OpenText("inventory.txt")
Dim strInventory = objMyStreamReader.ReadLine()
objMyStreamReader.Close()
txtManufacturer.AppendText(strInventory)
End Sub
这就是我目前将数据保存到文本文件的方式。
frmItemEntry.vb
Private Sub btnSave_Click(sender As Object, e As EventArgs) Handles btnSave.Click
Dim objMyStreamReader As System.IO.StreamReader
Dim objMyStreamWriter As System.IO.StreamWriter = System.IO.File.CreateText("inventory.txt")
Dim strInventory As String
objMyStreamWriter.WriteLine(txtManufacturerEntry.Text)
objMyStreamWriter.WriteLine(txtProcessorEntry.Text)
objMyStreamWriter.WriteLine(txtVideoEntry.Text)
objMyStreamWriter.WriteLine(txtFormEntry.Text)
objMyStreamWriter.WriteLine(txtRamEntry.Text)
objMyStreamWriter.WriteLine(txtVramEntry.Text)
objMyStreamWriter.WriteLine(txtHdEntry.Text)
objMyStreamWriter.WriteLine(chkWirelessEntry.CheckState)
objMyStreamWriter.Close()
Me.Close()
End Sub
来自inventory.txt的示例
Dell
i5
Nvidia
Desktop
8
4
600
0
老实说,控件永远不应该用作程序中数据的主要存储。 您确实应该创建一个类和该类的列表来存储您的数据。
然后,您可以将您的数据从您的文件读入列表,然后从那里在您的表单中显示它。
有多种方法可以浏览数据和保存更新。 下面的建议使用下一项和上一项的按钮,以及保存更新文件的按钮。
这一切都是不言自明的,但是如果您不确定某些事情,请使用谷歌并学习新的东西:-D
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
ReadDataFile()
DisplayItem(0)
End Sub
Private Class InventoryItem
Public Property Manufacturer As String
Public Property Processor As String
Public Property Video As String
Public Property FormFactor As String
Public Property Ram As String
Public Property VRam As String
Public Property Hd As String
Public Property Wireless As CheckState
Public Sub New()
Manufacturer = ""
Processor = ""
Video = ""
FormFactor = ""
Ram = ""
VRam = ""
Hd = ""
Wireless = CheckState.Unchecked
End Sub
End Class
Dim Inventory As New List(Of InventoryItem)
Dim currentItemIndex As Integer
Private Sub ReadDataFile()
Using objMyStreamReader As New StreamReader("k:\inventory.txt")
Do Until objMyStreamReader.EndOfStream
Dim newItem As New InventoryItem
newItem.Manufacturer = objMyStreamReader.ReadLine()
newItem.Processor = objMyStreamReader.ReadLine()
newItem.Video = objMyStreamReader.ReadLine()
newItem.FormFactor = objMyStreamReader.ReadLine()
newItem.Ram = objMyStreamReader.ReadLine()
newItem.VRam = objMyStreamReader.ReadLine()
newItem.Hd = objMyStreamReader.ReadLine()
Dim wirelessValue As String = objMyStreamReader.ReadLine()
If wirelessValue = "0" Then
newItem.Wireless = CheckState.Unchecked
ElseIf wirelessValue = "1" Then
newItem.Wireless = CheckState.Checked
End If
Inventory.Add(newItem)
Loop
End Using
End Sub
Private Sub SaveDataFile()
Using objMyStreamWriter As New System.IO.StreamWriter("k:\inventory.txt", False)
For Each item As InventoryItem In Inventory
objMyStreamWriter.WriteLine(item.Manufacturer)
objMyStreamWriter.WriteLine(item.Processor)
objMyStreamWriter.WriteLine(item.Video)
objMyStreamWriter.WriteLine(item.FormFactor)
objMyStreamWriter.WriteLine(item.Ram)
objMyStreamWriter.WriteLine(item.VRam)
objMyStreamWriter.WriteLine(item.Hd)
If item.Wireless = CheckState.Checked Then
objMyStreamWriter.WriteLine("1")
Else
objMyStreamWriter.WriteLine(0)
End If
Next
End Using
End Sub
Private Sub DisplayItem(index As Integer)
With Inventory(index)
txtManufacturerEntry.Text = .Manufacturer
txtProcessorEntry.Text = .Processor
txtVideoEntry.Text = .Video
txtFormEntry.Text = .FormFactor
txtRamEntry.Text = .Ram
txtVramEntry.Text = .VRam
txtHdEntry.Text = .Hd
chkWirelessEntry.CheckState = .Wireless
End With
End Sub
Private Sub BtnUpdateItem_Click(sender As Object, e As EventArgs) Handles BtnUpdateItem.Click
With Inventory(currentItemIndex)
.Manufacturer = txtManufacturerEntry.Text
.Processor = txtProcessorEntry.Text
.Video = txtVideoEntry.Text
.FormFactor = txtFormEntry.Text
.Ram = txtRamEntry.Text
.VRam = txtVramEntry.Text
.Hd = txtHdEntry.Text
.Wireless = chkWirelessEntry.CheckState
End With
SaveDataFile()
End Sub
Private Sub BtnPreviousItem_Click(sender As Object, e As EventArgs) Handles BtnPreviousItem.Click
If currentItemIndex > 0 Then
currentItemIndex -= 1
DisplayItem(currentItemIndex)
End If
End Sub
Private Sub BtnNextItem_Click(sender As Object, e As EventArgs) Handles BtnNextItem.Click
If currentItemIndex < Inventory.Count - 1 Then
currentItemIndex -= 1
DisplayItem(currentItemIndex)
End If
End Sub
首先更改文本文件的格式。
Dell,i5,Nvidia,Desktop,8,2,600,True
Acer,i7,Intel,Desktop,16,4,1GB,True
HP,Pentium,Diamond Viper,Desktop,4,2,200,False
Surface Pro,i7,Intel,Laptop,8,2,500,True
每一行都是一条记录,记录中的每个字段都用逗号分隔(没有空格,所以我们不必在代码中使用 .Trim)(字段中的空格很好,注意 Surface Pro)。
现在更容易在代码中读取文件。
此解决方案使用BindingSource
和DataBindings
。 这简化了导航以及编辑和保存数据。
Public Class Form5
Private bs As BindingSource
Private dt As New DataTable
#Region "Set Up the Form"
Private Sub Form5_Load(sender As Object, e As EventArgs) Handles MyBase.Load
AddColumnsToDataTable()
FillDataTable()
AddDataBindings()
End Sub
Private Sub AddColumnsToDataTable()
'Prepare the DataTable to hold data
dt.Columns.Add("Manufacturer", GetType(String))
dt.Columns.Add("Processor", GetType(String))
dt.Columns.Add("Video", GetType(String))
dt.Columns.Add("Form", GetType(String))
dt.Columns.Add("RAM", GetType(String))
dt.Columns.Add("VRAM", GetType(String))
dt.Columns.Add("HD", GetType(String))
dt.Columns.Add("Wireless", GetType(Boolean))
End Sub
Private Sub FillDataTable()
'ReadAllLines returns an array of the lines in a text file
'inventory.txt is stored in the bin\Debug folder of your project
'This is the current directory so it does not require a full path.
Dim lines = File.ReadAllLines("inventory.txt")
'Now it is easy to split each line into fields by using the comma
For Each line As String In lines
'Split returns an array of strings with the value of each field
Dim items = line.Split(","c)
'Each item in the array can be added as a field to the DataTable row
dt.Rows.Add(items(0), items(1), items(2), items(3), items(4), items(5), items(6), CBool(items(7)))
'Notice that the last element is changed from a string to a boolean. This is
'the Wireless field which is bound to the check box. The string "True" or "False" is
'changed to a Boolean so it can be used as the .Checked property (see bindings)
Next
End Sub
Private Sub AddDataBindings()
'Create a new instance of the BindingSource class
bs = New BindingSource()
'Set the DataSource to the DataTable we just filled
bs.DataSource = dt
'Now you can set the bindings of each control
'The .Add method takes (Name of Property to Bind, the BindingSource to use, The Field name
'from the DataTable.
txtForm.DataBindings.Add("Text", bs, "Form")
txtHd.DataBindings.Add("Text", bs, "HD")
txtManufacturer.DataBindings.Add("Text", bs, "Manufacturer")
txtProcessor.DataBindings.Add("Text", bs, "Processor")
txtRam.DataBindings.Add("Text", bs, "RAM")
txtVideo.DataBindings.Add("Text", bs, "Video")
txtVram.DataBindings.Add("Text", bs, "VRAM")
'Notice on the CheckBox we are using the Checked property.
chkWireless.DataBindings.Add("Checked", bs, "Wireless")
End Sub
#End Region
Private Sub btnAdd_Click(sender As Object, e As EventArgs) Handles btnAdd.Click
'Add a blank row to the DataTable
'A Boolean is like a number, a String can be Nothing but a Boolean must
'have a value so we pass in False.
dt.Rows.Add(Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, False)
'Find the position of the last row
Dim i As Integer = bs.Count - 1
'Move to the new empty row
bs.Position = i
End Sub
#Region "Navigation Code"
Private Sub btnPrevious_Click(sender As Object, e As EventArgs) Handles btnPrevious.Click
'The binding source Position determins where in the data you are
'It starts at zero
If bs.Position = 0 Then
MessageBox.Show("This is the first item.")
Return 'This exits the sub, you can use Exit Sub in vb
'but Return is common in other languages so it is good to learn
Else
'As the position of the BindingSource changes the boud TextBoxes
'change their data.
bs.Position = bs.Position - 1
End If
End Sub
Private Sub btnNext_Click(sender As Object, e As EventArgs) Handles btnNext.Click
' If you are not at the end of the list, move to the next item
' in the BindingSource.
If bs.Position + 1 < bs.Count Then
bs.MoveNext()
' Otherwise, move back to the first item.
Else
bs.MoveFirst()
End If
End Sub
#End Region
#Region "Save the Data"
Private Sub SaveDataTable()
'Resave the whole file if this was a real app you would use a database
Dim sb As New StringBuilder
'A string builder keeps the code from creating lots of new strings
'Strings are immutable (can't be changed) so every time you think you are
'changing a string, you are actually creating a new one.
'The string builder is mutable (changable)
For Each row As DataRow In dt.Rows
'The ItemsArray returns an array of objects containing all the
'values in each column of the data table.
Dim rowValues = row.ItemArray
'This is a bit of Linq magic that turns the values (objects) into strings
'Underneath it is performing a For loop on each object in the array
Dim strRowValues = From o In rowValues
Select Convert.ToString(o)
'Now that we have strings we can use the String.Join with the comma
'to get the format of the text file
sb.AppendLine(String.Join(",", strRowValues))
Next
'Finally we change the StringBuilder to a real String
'The inventory.txt is stored in the bin\Debug directory so it is current directory
'no additional path required
File.WriteAllText("inventory.txt", sb.ToString)
End Sub
Private Sub Form5_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
'Because our binding is two-way any additions or changes to the text
'in the text boxes or check box are reflected in the DataTable.
SaveDataTable()
End Sub
#End Region
End Class
删除注释后,这里的代码真的很少。 #Region...#End Region
标签使您可以轻松折叠您#Region...#End Region
代码部分并快速找到区域。
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