首先vb.net是一種編程語言，它自己是沒有的。
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但vb.net與c#、vc++.net等其它編程語言共用一個公共類庫（叫框架類庫），這個類庫在命名空間System中提供了一個類叫Math（Public NotInheritable Class Math）。它為三角函數(shù)、對數(shù)函數(shù)和其他通用數(shù)學(xué)函數(shù)提供了常數(shù)和靜態(tài)方法，其中就包括Max。
使用datediff函數(shù)
textbox3.text=datediff("d","textbox1.text","textbox2.text")
說明一下：
“d”表示“天”
還可以用“y”,"m","d","h","n","s"
分別表示“年”“月”“日”“時”“分”“秒”
僅僅是普通表達式的話，定義數(shù)據(jù)類型，比如從單精度改為雙精度，如果想保留小數(shù)點位數(shù)，用formatnumber來處理。如果是某個算法的精度，就要復(fù)雜一些，要定義一個誤差，在算法迭代過程中，用while語句判斷計算結(jié)果的殘差是否小于定義的誤差值，至于殘差如何計算，與你的算法有關(guān)
Public Class SimpleCalculator
Inherits System.Windows.Forms.Form
#Region " Windows 窗體設(shè)計器生成的代碼 "
Public Sub New()
MyBase.New()
'該調(diào)用是 Windows 窗體設(shè)計器所必需的。
InitializeComponent()
'在 InitializeComponent() 調(diào)用之后添加任何初始化
End Sub
'窗體重寫處置以清理組件列表。
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Dispose()
End If
End If
MyBase.Dispose(disposing)
End Sub
'Windows 窗體設(shè)計器所必需的
Private components As System.ComponentModel.IContainer
'注意：以下過程是 Windows 窗體設(shè)計器所必需的
'可以使用 Windows 窗體設(shè)計器修改此過程。
'不要使用代碼編輯器修改它。
Friend WithEvents Label1 As System.Windows.Forms.Label
Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
Friend WithEvents Button1 As System.Windows.Forms.Button
Friend WithEvents Button2 As System.Windows.Forms.Button
Friend WithEvents Button3 As System.Windows.Forms.Button
Friend WithEvents Button4 As System.Windows.Forms.Button
Friend WithEvents Button5 As System.Windows.Forms.Button
Friend WithEvents Button6 As System.Windows.Forms.Button
Friend WithEvents Button7 As System.Windows.Forms.Button
Friend WithEvents Button8 As System.Windows.Forms.Button
Friend WithEvents Button9 As System.Windows.Forms.Button
Friend WithEvents Button10 As System.Windows.Forms.Button
Friend WithEvents Button11 As System.Windows.Forms.Button
Friend WithEvents Button12 As System.Windows.Forms.Button
Friend WithEvents Button13 As System.Windows.Forms.Button
Friend WithEvents Button14 As System.Windows.Forms.Button
Friend WithEvents Button15 As System.Windows.Forms.Button
Friend WithEvents Button16 As System.Windows.Forms.Button
System.Diagnostics.DebuggerStepThrough() Private Sub InitializeComponent()
Me.Label1 = New System.Windows.Forms.Label
Me.TextBox1 = New System.Windows.Forms.TextBox
Me.Button1 = New System.Windows.Forms.Button
Me.Button2 = New System.Windows.Forms.Button
Me.Button3 = New System.Windows.Forms.Button
Me.Button4 = New System.Windows.Forms.Button
Me.Button5 = New System.Windows.Forms.Button
Me.Button6 = New System.Windows.Forms.Button
Me.Button7 = New System.Windows.Forms.Button
Me.Button8 = New System.Windows.Forms.Button
Me.Button9 = New System.Windows.Forms.Button
Me.Button10 = New System.Windows.Forms.Button
Me.Button11 = New System.Windows.Forms.Button
Me.Button12 = New System.Windows.Forms.Button
Me.Button13 = New System.Windows.Forms.Button
Me.Button14 = New System.Windows.Forms.Button
Me.Button15 = New System.Windows.Forms.Button
Me.Button16 = New System.Windows.Forms.Button
Me.SuspendLayout()
'
'Label1
'
Me.Label1.Location = New System.Drawing.Point(16, 16)
Me.Label1.Name = "Label1"
Me.Label1.Size = New System.Drawing.Size(48, 16)
Me.Label1.TabIndex = 0
Me.Label1.Text = "結(jié)果："
'
'TextBox1
'
Me.TextBox1.Location = New System.Drawing.Point(64, 8)
Me.TextBox1.Name = "TextBox1"
Me.TextBox1.Size = New System.Drawing.Size(120, 21)
Me.TextBox1.TabIndex = 1
Me.TextBox1.Text = ""
'
'Button1
'
Me.Button1.Location = New System.Drawing.Point(200, 8)
Me.Button1.Name = "Button1"
Me.Button1.Size = New System.Drawing.Size(56, 24)
Me.Button1.TabIndex = 2
Me.Button1.Text = "清空"
'
'Button2
'
Me.Button2.Location = New System.Drawing.Point(48, 56)
Me.Button2.Name = "Button2"
Me.Button2.Size = New System.Drawing.Size(24, 24)
Me.Button2.TabIndex = 3
Me.Button2.Text = "1"
'
'Button3
'
Me.Button3.Location = New System.Drawing.Point(88, 56)
Me.Button3.Name = "Button3"
Me.Button3.Size = New System.Drawing.Size(24, 24)
Me.Button3.TabIndex = 4
Me.Button3.Text = "2"
'
'Button4
'
Me.Button4.Location = New System.Drawing.Point(136, 56)
Me.Button4.Name = "Button4"
Me.Button4.Size = New System.Drawing.Size(24, 24)
Me.Button4.TabIndex = 5
Me.Button4.Text = "3"
'
'Button5
'
Me.Button5.Location = New System.Drawing.Point(48, 88)
Me.Button5.Name = "Button5"
Me.Button5.Size = New System.Drawing.Size(24, 24)
Me.Button5.TabIndex = 6
Me.Button5.Text = "4"
'
'Button6
'
Me.Button6.Location = New System.Drawing.Point(88, 88)
Me.Button6.Name = "Button6"
Me.Button6.Size = New System.Drawing.Size(24, 24)
Me.Button6.TabIndex = 7
Me.Button6.Text = "5"
'
'Button7
'
Me.Button7.Location = New System.Drawing.Point(136, 88)
Me.Button7.Name = "Button7"
Me.Button7.Size = New System.Drawing.Size(24, 24)
Me.Button7.TabIndex = 8
Me.Button7.Text = "6"
'
'Button8
'
Me.Button8.Location = New System.Drawing.Point(48, 120)
Me.Button8.Name = "Button8"
Me.Button8.Size = New System.Drawing.Size(24, 24)
Me.Button8.TabIndex = 9
Me.Button8.Text = "7"
'
'Button9
'
Me.Button9.Location = New System.Drawing.Point(88, 120)
Me.Button9.Name = "Button9"
Me.Button9.Size = New System.Drawing.Size(24, 24)
Me.Button9.TabIndex = 10
Me.Button9.Text = "8"
'
'Button10
'
Me.Button10.Location = New System.Drawing.Point(136, 120)
Me.Button10.Name = "Button10"
Me.Button10.Size = New System.Drawing.Size(24, 24)
Me.Button10.TabIndex = 11
Me.Button10.Text = "9"
'
'Button11
'
Me.Button11.Location = New System.Drawing.Point(48, 152)
Me.Button11.Name = "Button11"
Me.Button11.Size = New System.Drawing.Size(24, 24)
Me.Button11.TabIndex = 12
Me.Button11.Text = "0"
'
'Button12
'
Me.Button12.Location = New System.Drawing.Point(176, 56)
Me.Button12.Name = "Button12"
Me.Button12.Size = New System.Drawing.Size(24, 24)
Me.Button12.TabIndex = 13
Me.Button12.Text = "+"
'
'Button13
'
Me.Button13.Location = New System.Drawing.Point(176, 88)
Me.Button13.Name = "Button13"
Me.Button13.Size = New System.Drawing.Size(24, 24)
Me.Button13.TabIndex = 14
Me.Button13.Text = "-"
'
'Button14
'
Me.Button14.Location = New System.Drawing.Point(176, 120)
Me.Button14.Name = "Button14"
Me.Button14.Size = New System.Drawing.Size(24, 24)
Me.Button14.TabIndex = 15
Me.Button14.Text = "*"
'
'Button15
'
Me.Button15.Location = New System.Drawing.Point(176, 152)
Me.Button15.Name = "Button15"
Me.Button15.Size = New System.Drawing.Size(24, 24)
Me.Button15.TabIndex = 16
Me.Button15.Text = "/"
'
'Button16
'
Me.Button16.Location = New System.Drawing.Point(88, 152)
Me.Button16.Name = "Button16"
Me.Button16.Size = New System.Drawing.Size(72, 24)
Me.Button16.TabIndex = 17
Me.Button16.Text = "計算"
'
'SimpleCalculator
'
Me.AutoScaleBaseSize = New System.Drawing.Size(6, 14)
Me.ClientSize = New System.Drawing.Size(264, 190)
Me.Controls.Add(Me.Button16)
Me.Controls.Add(Me.Button15)
Me.Controls.Add(Me.Button14)
Me.Controls.Add(Me.Button13)
Me.Controls.Add(Me.Button12)
Me.Controls.Add(Me.Button11)
Me.Controls.Add(Me.Button10)
Me.Controls.Add(Me.Button9)
Me.Controls.Add(Me.Button8)
Me.Controls.Add(Me.Button7)
Me.Controls.Add(Me.Button6)
Me.Controls.Add(Me.Button5)
Me.Controls.Add(Me.Button4)
Me.Controls.Add(Me.Button3)
Me.Controls.Add(Me.Button2)
Me.Controls.Add(Me.Button1)
Me.Controls.Add(Me.TextBox1)
Me.Controls.Add(Me.Label1)
Me.Name = "SimpleCalculator"
Me.Text = "簡單計算器"
Me.ResumeLayout(False)
End Sub
#End Region
Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
End Sub
Private Sub TextBox1_TabStopChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Dim btn As Button '按鈕類型的變量
btn = sender '把產(chǎn)生該事件的按鈕對象賦值給btn
TextBox1.Text = TextBox1.Text + btn.Text '把該按鈕的Text屬性值連接到TextBox1中
End Sub
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
Dim btn As Button
btn = sender
TextBox1.Text += btn.Text
End Sub
Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
Dim btn As Button
btn = sender
TextBox1.Text += btn.Text
End Sub
Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
Dim btn As Button
btn = sender
TextBox1.Text += btn.Text
End Sub
Private Sub Button6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button6.Click
Dim btn As Button
btn = sender
TextBox1.Text += btn.Text
End Sub
Private Sub Button7_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button7.Click
Dim btn As Button
btn = sender
TextBox1.Text += btn.Text
End Sub
Private Sub Button8_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button8.Click
Dim btn As Button
btn = sender
TextBox1.Text += btn.Text
End Sub
Private Sub Button9_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button9.Click
Dim btn As Button
btn = sender
TextBox1.Text += btn.Text
End Sub
Private Sub Button10_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button10.Click
Dim btn As Button
btn = sender
TextBox1.Text += btn.Text
End Sub
Private Sub Button11_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button11.Click
Dim btn As Button
btn = sender
TextBox1.Text += btn.Text
End Sub
Private Sub Button12_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button12.Click
Dim btn As Button
btn = sender
'在文本框的Text屬性后連接一個空格、本按鈕的Text屬性值和一個空格
TextBox1.Text = TextBox1.Text + " " + btn.Text + " "
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
TextBox1.Text = "" '清空文本框
End Sub
Private Sub Button13_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button13.Click
Dim btn As Button
btn = sender
TextBox1.Text = TextBox1.Text + " " + btn.Text + " "
End Sub
Private Sub Button14_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button14.Click
Dim btn As Button
btn = sender
TextBox1.Text = TextBox1.Text + " " + btn.Text + " "
End Sub
Private Sub Button15_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button15.Click
Dim btn As Button
btn = sender
TextBox1.Text = TextBox1.Text + " " + btn.Text + " "
End Sub
Private Sub Button16_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button16.Click
'發(fā)生錯誤轉(zhuǎn)移到標號“ErrorPro”指定的行去執(zhí)行錯誤處理程序
On Error GoTo ErrorPro
Dim r As Decimal '保存計算結(jié)果的變量
Dim t As String = TextBox1.Text '用于保存文本框中的算術(shù)表達式
Dim space As Integer = t.IndexOf(" ") '搜索空格位置,如果沒有空格，返回值為0
'字符串的取子符方法，第二個參數(shù)小于0，則將產(chǎn)生錯誤號為5的異常，即過程參數(shù)不正確
Dim s1 As String = t.Substring(0, space) '通過取子串方法獲得第一個運算數(shù)
Dim op As String = t.Substring(space + 1, 1) '通過取子串方法獲得運算符
Dim s2 As String = t.Substring(space + 3) '通過取子串方法獲得第二個運算數(shù)
Dim arg1, arg2 As Integer
arg1 = Val(s1) : arg2 = Val(s2)
Select Case op
Case "+" : r = arg1 + arg2
Case "-" : r = arg1 - arg2
Case "*" : r = arg1 * arg2
Case "/" : r = arg1 / arg2
Case Else
MsgBox("輸入的運算符有誤！")
Exit Sub
End Select
TextBox1.Text = CStr(r) '顯示結(jié)果
Exit Sub '退出過程
ErrorPro: '錯誤處理程序塊
Select Case Err.Number
Case 6 '除數(shù)為零時，或運算溢出時的錯誤號
MsgBox("算術(shù)運算溢出！", , "溢出提示")
TextBox1.Focus()
Exit Sub
Case 5 ' Substring過程的參數(shù)不符合要求的錯誤號
MsgBox("必須輸入運算符和第二個運算數(shù)！", , "運算數(shù)少")
Exit Sub
Case Else
'其它情況顯示錯誤號和錯誤原因
MsgBox("錯誤號為" Err.Number Chr(10) Chr(13) "錯誤原因：" Err.Description)
Exit Sub
End Select
End Sub
End Class
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