Printable View
I have a public readonly variable in a module, but when I try to set it in my form load event for the first time I get 'ReadOnly' variable cannot be the target of an assignment.
It is my understanding that a ReadOnly variable can only be set once and after that you would get an error when setting it.
I think you can only initialize ReadOnly fields when declaring them, or in the constructor:
orCode:Public ReadOnly Name As String = "ABC"
Since you are talking about a module, only the first is an option.Code:Public Readonly Name As String
Public Sub New()
Name = "ABC"
End Sub
If you do need to set the value at a later stage, consider a ReadOnly property instead. You can still make the private backing field writable:
Now you can set the backing field to change the value of the property from within the same class (obviously not outside of the class).Code:Private _Name As String
Public ReadOnly Property Name() As String
Get
Return _Name
End Get
End Property
In the same class, you can read and write:
From the outside, any other class, you can only read:Code:'Read
MsgBox(Me.Name)
'Write
_Name = "DEF"
Code:'Read
MsgBox(classInstance.Name)
'Write
classInstance.Name = "DEF" ' readonly error (Name is readonly)
classInstance._Name = "DEF" ' access modifier error (_Name is private)
This is another case when you simply need to consult the documentation.Quote:
Originally Posted by Disyne
http://msdn.microsoft.com/en-us/library/z2b2c2ka.aspxQuote:
You can assign a value to a ReadOnly variable only in its declaration or in the constructor of a class or structure in which it is defined.