试图让一个类返回一个字符串

Question

我正在将代码从代码隐藏到类并运行到一个问题。我有一个方法，使一个字符串（一个HTML发票）。在该方法中，创建最终的金额。我想创建一个名为Invoice的类，该类将具有“CreateInvoice”方法，该方法将返回一个字符串，并且还希望设置该对象的finalCharge属性。我把所有的繁重做，但它是建立类是

Public Class Invoice 
    Public finalCharge As Double 
    Public invoiceString As String 
    Public billingId As Integer 
    Public clientID As Integer 

Public Shared Function CreateInvoice(ByVal bill_id As Integer, ByVal client_id As Integer) As String 
    ... 'create string invoice 
    ... 'tally final charge 
End Function 


'On my code-behind page. 
dim y as string 
dim x as Invoice 

y = x.CreateInvoice(1225,8855) <-- this line doesn't work. 

谢谢你的帮助来获得整理出我有麻烦的一部分！

Answer 1

这是一个Shared函数 - 这意味着你不需要（或想要）该类的一个实例来使用它。你应该把它想：

Invoice.CreateInvoice(1225, 8855) 

这就是说，我不能完全肯定这应该是Shared，首先，因为你也状态：

[I] ...想设置在finalCharge财产

由于Shared功能只能访问Shared特性（因为没有实例），你可能真的希望它是一个实例函数：

Public Class Invoice 
    Public finalCharge As Double 
    Public invoiceString As String 
    Public billingId As Integer 
    Public clientID As Integer 

    Public Function CreateInvoice(ByVal bill_id As Integer, ByVal client_id As Integer) As String 
     ... 'create string invoice 
     Me.finalCharge = ... 'tally final charge 
    End Function 
End Class 

在这种情况下，你把它想：

Dim x as New Invoice() 
Dim y as String = x.CreateInvoice(1225, 8855) 
Dim finalCharge as Double = x.finalCharge