VB.net的开方运算

VB的运算顺序是：先乘除、后加减，有括号的先算括号内，有负号的先算负号。

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请你比较一下这个运算中x和y的值：

Dim n As Single = 4

Dim x As Single

Dim y As Single

x = n + 1

x = x / n

x = x - 1

x = Math.Sqrt(x)

y = Math.Sqrt((n + 1) / n - 1)

这样就会发现，你的代码中括号的位置错了。

正确的应该是： Math.Sqrt((n + 1) / n - 1)

VB.NET 如何绘制数学代数式（公式、方程、函数解析式等）？

绝对值是“|”，可以直接显示，同理对数可用log(x)代替，根号和其他不支持显示。

如果要显示数学式子，只能画吧。

计算时可用“^”求幂或求根，“/”表示除法和分数线，还有math类。

用VB.NET编的计算器程序！

Public Class SimpleCalculator

Inherits System.Windows.Forms.Form

#Region " Windows 窗体设计器生成的代码 "

Public Sub New()

MyBase.New()

'该调用是 Windows 窗体设计器所必需的。

InitializeComponent()

'在 InitializeComponent() 调用之后添加任何初始化

End Sub

'窗体重写处置以清理组件列表。

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 窗体设计器所必需的

Private components As System.ComponentModel.IContainer

'注意：以下过程是 Windows 窗体设计器所必需的

'可以使用 Windows 窗体设计器修改此过程。

'不要使用代码编辑器修改它。

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 = "结果："

'

'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 = "计算"

'

'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 = "简单计算器"

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 '按钮类型的变量

btn = sender '把产生该事件的按钮对象赋值给btn

TextBox1.Text = TextBox1.Text + btn.Text '把该按钮的Text属性值连接到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属性后连接一个空格、本按钮的Text属性值和一个空格

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

'发生错误转移到标号“ErrorPro”指定的行去执行错误处理程序

On Error GoTo ErrorPro

Dim r As Decimal '保存计算结果的变量

Dim t As String = TextBox1.Text '用于保存文本框中的算术表达式

Dim space As Integer = t.IndexOf(" ") '搜索空格位置,如果没有空格，返回值为0

'字符串的取子符方法，第二个参数小于0，则将产生错误号为5的异常，即过程参数不正确

Dim s1 As String = t.Substring(0, space) '通过取子串方法获得第一个运算数

Dim op As String = t.Substring(space + 1, 1) '通过取子串方法获得运算符

Dim s2 As String = t.Substring(space + 3) '通过取子串方法获得第二个运算数

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("输入的运算符有误！")

Exit Sub

End Select

TextBox1.Text = CStr(r) '显示结果

Exit Sub '退出过程

ErrorPro: '错误处理程序块

Select Case Err.Number

Case 6 '除数为零时，或运算溢出时的错误号

MsgBox("算术运算溢出！", , "溢出提示")

TextBox1.Focus()

Exit Sub

Case 5 ' Substring过程的参数不符合要求的错误号

MsgBox("必须输入运算符和第二个运算数！", , "运算数少")

Exit Sub

Case Else

'其它情况显示错误号和错误原因

MsgBox("错误号为" Err.Number Chr(10) Chr(13) "错误原因：" Err.Description)

Exit Sub

End Select

End Sub

End Class

vb.net 中，怎麼做拉动线段的功能 ??

效果如图，代码如下：

Public Class Form1

'Circle类

Class Circle

  Public Center As Point

  Public Radius As Single

  Public Sub New(c As Point, r As Single)

      Center = c

      Radius = r

  End Sub

  '绘制

  Public Sub Draw(g As Graphics, pen As Pen)

      g.DrawEllipse(pen, New RectangleF(Center.X - Radius, Center.Y - Radius, Radius * 2, Radius * 2))

  End Sub

End Class

Private downPoint As Point      '记录鼠标按下位置

Private circleList As New List(Of Circle)       '已存放圆的列表

Private tmpCircle As Circle     '临时圆（正在拖动）

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

  DoubleBuffered = True       '启用双缓冲绘图，避免闪烁

End Sub

Private Sub Form1_MouseDown(sender As Object, e As MouseEventArgs) Handles Me.MouseDown

  downPoint = e.Location      '记下位置

End Sub

Private Sub Form1_MouseMove(sender As Object, e As MouseEventArgs) Handles Me.MouseMove

  If e.Button  Windows.Forms.MouseButtons.Left Then Return '左键没按下则退出

  Dim r As Single = Math.Sqrt((e.X - downPoint.X) ^ 2 + (e.Y - downPoint.Y) ^ 2)  '算出半径

  tmpCircle = New Circle(downPoint, r)            '更新临时圆

  Refresh()                                       '先刷新掉之前绘制的临时圆

  tmpCircle.Draw(Me.CreateGraphics, Pens.Black)   '绘制临时圆

End Sub

Private Sub Form1_MouseUp(sender As Object, e As MouseEventArgs) Handles Me.MouseUp

  circleList.Add(tmpCircle)           '鼠标弹起，把临时圆加入圆列表

End Sub

Private Sub Form1_Paint(sender As Object, e As PaintEventArgs) Handles Me.Paint

  For Each c As Circle In circleList

      c.Draw(e.Graphics, Pens.Black)  '绘制出每个圆

  Next

End Sub

End Class

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