VS Designer and constructors with parameters

Question

I have a custom control MyControl. Has a parameterless constructor (Sub New() in VB).

I place that control in a WinForm.

No problems.

Now, want a parameter in that constructor. Sub New(flag as Boolean)

How should I deal with VS designer in that case, in order to be able to open that form in Designer?

I did in myForm the following

  Public Sub New()
    MyBase.New()
    Me.MyControl_1 = New MyControl(True)
    Me.InitializeComponent()

but the Designer says:

The variable 'MyControl_1' is either undeclared or was never assigned.

score 2 · Accepted Answer · edited May 23 '17 at 12:20

2

The designer requires a parameterless constructor for visual components. Even adding an overloaded constructor to a user control will break the designer. See this question for more information.

edited May 23 '17 at 12:20

Community

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answered Feb 15 '11 at 13:46

AJ.

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yeah. I understand. But I can't use properties, because I have a control "mode" that can't be changed after its creation. (like readonly one). So I can't and wouldn't use properties. I need this "mode" be set only once, as earlier as possible. So I search a workaround. – serhio Feb 15 '11 at 14:26
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an overloaded constructor does NOT break the designer, as long as there is also a parameterless constructor – yoel halb Jan 01 '14 at 19:01

score 1 · Answer 2 · answered Feb 15 '11 at 13:47

1

Modify to this

Public Sub New()
    MyBase.New()
    Me.InitializeComponent()
    Me.MyControl_1 = New MyControl(True)

Let designer initialize the cotrol before you use it. Problem is not with your control, problem is you are not using at right place.

answered Feb 15 '11 at 13:47

hungryMind

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I am afraid that if I'll reinitialize it after, I will loose it from its containers. – serhio Feb 15 '11 at 14:05
and. I loose all the designer parameters – serhio Feb 15 '11 at 14:47
In that case, why not simply have a method which will do all what you trying to do in ctor. And call it after InitializeComponent – hungryMind Feb 15 '11 at 16:59

VS Designer and constructors with parameters

2 Answers2