在VB中使用參數和類遇到麻煩

Question

我在使類工作並為這些類傳遞參數時遇到麻煩。 我已經找出了我自己遇到的其他大多數錯誤，但是確實有一個錯誤困擾着我。 我得到的錯誤是“ objAttendee”的。 錯誤顯示為“未為公共Sub New（ByVal strFirstName作為字符串，ByVal strLastName作為字符串，ByVal strCourses作為字符串，ByVal intDays作為字符串）的公共Sub New的參數” strFirstName”指定參數的參數”。 我完全不確定如何解決此問題。

有人可以幫我嗎？

Option Strict On

Public Class Attendee
    Dim objAttendee As New Attendee

    'class variables
    Private _strFirstName As String
    Private _strLastName As String
    Private _strCourses As String
    Private _intDays As Integer
    Private _decTotal As Decimal
    Private _decCostPerDay As Decimal = 350D
    Private _decPreConferenceCost As Decimal = 675D

    Sub New(ByVal strFirstName As String, ByVal strLastName As String, ByVal strCourses As String, ByVal intDays As String)
        'Contructor


        _strFirstName = strFirstName
        _strLastName = strLastName
        _strCourses = strCourses
        _intDays = Convert.ToInt32(intDays)

    End Sub

    Function ComputeCourseCosts() As Decimal

        'Calculates the cost if a pre-conference course is not selected
        _decTotal = _intDays * _decCostPerDay

        Return _decTotal
    End Function

    Function ComputePreConferenceCosts() As Decimal

        'Calculates the cost if a pre-conference course is selected
        _decTotal = _intDays * _decCostPerDay + _decPreConferenceCost

        Return _decTotal
    End Function
End Class

Answer 1

“未為參數指定參數“ .....

Plutonix告訴您問題的根源：

您正在您的Attendee類中聲明一個Attendee對象（這沒有任何意義）

Public Class Attendee
    Dim objAttendee As New Attendee ' <- offending code :P

但是該類的構造函數聲明如下：

    Sub New(ByVal strFirstName As String, ByVal strLastName As String, ByVal strCourses As String, ByVal intDays As String)

而且你沒有沒有像這樣的任何參數的構造函數：

    Public Sub New() ' No parameter required
        ' ...
    End Sub

並且您不必創建/聲明Attendee構造函數的這種變體，否則， 必須為_strFirstName ， _strLastName ， _strCourses和_intDays 定義默認值 ！

我認為 ...你在沖動測試與會者類，並宣布它里面的與會者變量）。

不，您應該 使用適當的參數在類外部（例如，在程序的主塊中Dim objAttendee As New Attendee(...)將Dim objAttendee As New Attendee(...)聲明Dim objAttendee As New Attendee(...) 。

    Private Sub ShowMyClass(sender As Object, e As EventArgs) Handles Button1.Click
        Dim objAttendee As New Attendee("Simpson", "Homer", "Courses", "48")

        MessageBox.Show(objAttendee.ComputeCourseCosts().ToString())
    End Sub