從共享（或靜態）函數調用等功能

Question

我得到這個錯誤：Cannot refer to an instance member of a class from within a shared method or shared member initializer without an explicit instance of the class.

Partial Class _Default 
    Inherits System.Web.UI.Page 

    <WebMethod()> _ 
    Public Shared Function ParseData() As String 
     Dim value as string = GetValue() 
    End Function 

    Private Function GetValue() as String 
     Return "halp" 
    End Function 
End Class 

我知道它是與第一功能是共享的，第二個函數大概應該是這樣的事實公衆也是如此，但我不完全理解它背後的原因。可能不相關，但我從一些JavaScript調用Web方法。

Answer 1

Partial Class _Default 
    Inherits System.Web.UI.Page 

    <WebMethod()> _ 
    Public Shared Function ParseData() As String 
     Dim value as string = GetValue() 
    End Function 

    Private Shared Function GetValue() as String 
     Return "halp" 
    End Function 
End Class 

或

Partial Class _Default 
    Inherits System.Web.UI.Page 

    <WebMethod()> _ 
    Public Function ParseData() As String 
     Dim value as string = GetValue() 
    End Function 

    Private Function GetValue() as String 
     Return "halp" 
    End Function 
End Class 

如果它必須是共享的，則與第一個去。如果你可以先初始化對象，或者如果你是從同一個類中調用它的話，那就去第二個。

正如您所指出的，Webmethod必須是Shared（靜態）。在這種情況下，您從webmethod調用的方法也必須共享。

編輯：

另一種選擇是創建一個單獨的類「的GetValue」

Partial Class _Default 
    Inherits System.Web.UI.Page 

    <WebMethod()> _ 
    Public Shared Function ParseData() As String 
     Dim util As Utilities = New Utilities 
     Dim value as string = util.GetValue() 
    End Function 
End Class 

Public Class Utilities ''# Utilities is completely arbitrary, you can use whatever you like. 
    Public Function GetValue() as String 
     Return "halp" 
    End Function 
End Class