问题
I have written a custom ErrorProvider which adds some functionality to the existing ErrorProvider (sets control BackColor, ErrorCount etc). This was working find but now for some reason it falls over on the constructor:
_LoginErrorProvider = New ErrorLogErrorProvider(Me.components)
The error is a NullReferenceException which is caused by the fact that Me.components is Nothing. Can anyone shed any light on why a form's components collection would be Nothing? The form seems to work fine in every other way!
回答1:
when you add a component to the design surface it adds this in the InitializeComponent function
me.components = new System.ComponentModel.Container()
so just add this in your self.
or your
_LoginErrorProvider = New ErrorLogErrorProvider(Me.components)
is being called before InitializeComponent
回答2:
You can also drop your ErrorLogErrorProvider class onto the design surface for your Form / UserControl and the code generated for InitializeComponent will correctly initialize the components member and pass it to the constructor of your error provider (VS does this for all non-visual components). Just make sure that your ErrorLogErrorProvider class derives from either Component or implements the IComponent interface.
回答3:
Solved it, adding another component to the form seems to fix the problem, it's a bit of a cludge but works. I suppose the ideal solution would be to add my ErrorProvider to me.components but in order to do this you need to initialize a new instance which you can't because Me.components is Nothing!!
It could drive a man crazy.....
来源：https://stackoverflow.com/questions/516776/why-is-me-components-nothing