Imports System.Math
Public Class Form1
    Inherits System.Windows.Forms.Form
    Function SquareRoot(ByVal X As Double) As Double
        Select Case Sign(X)
            Case 1
                Return Sqrt(X)
            Case 0
                Return 0
            Case -1
                Return -1
        End Select
    End Function

#Region " Windows 窗體設計器生成的代碼 "

    Public Sub New()
        MyBase.New()

        '該調用是 Windows 窗體設計器所必需的。
        InitializeComponent()

        '在 InitializeComponent() 調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 窗體設計器所必需的
    Private components As System.ComponentModel.IContainer

    '注意：以下過程是 Windows 窗體設計器所必需的
    '可以使用 Windows 窗體設計器修改此過程。
    '不要使用代碼編輯器修改它。
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        '
        'Form1
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(6, 14)
        Me.ClientSize = New System.Drawing.Size(292, 273)
        Me.Name = "Form1"
        Me.Text = "Form1"

    End Sub

#End Region

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim Msg As String
        Dim SqrN As Short
        Dim N As Double
        N = InputBox("請輸入要計算平方根的數：")
        Msg = N & "的平方根"
        SqrN = Sign(N)
        Select Case SqrN
            Case 0
                Msg = Msg & "是0"
            Case -1
                Msg = Msg & "是一個虛數"
            Case Else
                Msg = Msg & "是" & Sqrt(N)
        End Select
        MsgBox(Msg, , "")
    End Sub
End Class