I have created a forms which are derived from another form thus:-
Public Class MyForm
' ...etc
End Class
Public Class MyDerivedForm
Inherits MyBaseForm
' ...etc
End Class
Public Class MyOtherDerivedForm
Inherits MyBaseForm
' ...etc
End Class
This works quite nicely and I can add controls to the derived form using the form designer. But I'd like to move some of the inherited controls around a bit on MyDerivedForm without disturbing MyBaseForm or MyOtherDerivedForm. I can't see any way of doing this on the forms designer.
Is it possible to do this (preferably with the designer but with code if necessary)?
This is not a typical VB.NET problem so not so sure what's going on here. You'll get the lock icon on the inherited controls and a grayed-out Properties window for an inherited control when the Modifiers property of the control in the base class is Private. The Winforms designer observes the accessibility of the base class member. Private members can't be messed with. The default value for Modifiers is Friend in VB.NET, Private in C#.
Make it Friend to allow the derived form class to modify the control properties. If the base form class lives in another assembly then Friend isn't good enough, you'll need Public.
The Anchor property can be an issue, but only if you anchor to the right or bottom. The control has a knack for ending up in the wrong spot when the derived form has a different size from the base form if the control is anchored that way. Simply avoided by not anchoring at the right/bottom in the base class and changing the anchor in the derived class.
In my VB.NET WinForms application I have inherited forms and I can just grab the inherited controls in the designer and move them about as I would with non-inherited controls on the form.
However I have noticed two things in the past that stop this. If you change the position of the controls on the base form, or change some of the positioning properties (such as anchor or docking), then this can (but not always) move your inherited controls. Also I couldn't move some of my inherited controls in an earlier version of .NET (2.0 I believe), but I never figured out the cause for that so I had to resort to changing the locations via the property grid.
Related
Setup:
I have created a Form that I wish to have serve as the base from which I will inherit other forms. This base form serves as a "template" of sorts, but it also provides a good deal of functionality related to the structure, as well as the interrelation of all of the controls provided.
A primer for the images that follow... The top info-colored bar is a custom control inherited from ToolStrip. The bottom strip is another custom, again inherited from ToolStrip. The left white block is a TreeView and the right block is a TabControl (having deleted all TabPages from it...I intend for these to be added in the inherited forms).
Image of base form in designer:
Image of inherited form in designer:
Clearly, the only difference is that when I open the inherited form, I get a little box icon superimposed over each control, and when I click them, I get the padlock telling me I cannot edit.
The problems:
All controls on the inherited form are locked. I have researched the issue of visual inheritance, and as far as I can tell, I'm not using any controls that expressly do not support it, as this link suggests there are. In this Q&A, Hans suggests changing the modifier on those controls, which I have done. In fact, I tried both Public and Protected, all to no good result.
I am stumped.
This is a technical restriction in the designer, it is specific to the SplitContainer control you are using. And some other ones. The trouble-maker is the ISupportInitialize interface.
Controls use this interface when they can't afford the properties of the control to be assigned in an arbitrary order. The designer helps when it sees that the control implements this interface, it calls the BeginInit() method when it starts assigning properties, EndInit() when it is done. The control uses these methods to delay the side-effect of property assignments, the EndInit() method makes them effective. Important for SplitContainer, the minimum sizes of the panels also affect the splitter position.
Perhaps you can see the rub, the InitializeComponent() method in the base form class has already called ISupportInitialize.EndInit(). So modifying properties again in the derived form class is unlikely to turn out well. The designer protects the control from this by locking it.
Very inconvenient, there is no simple workaround. If modifying the SplitContainer in the derived form class is a hard requirement then you'll have to give up on inheriting it or write the code by hand in the derived class constructor.
I have an existing project in VB.net with many Windows forms.I want to change all forms to deriven from a base form created in a class library.
is there any way to do so?
if i do inheritance with a code like this the designer dose not show the child form and gets error
Class Form1
Inherits BaseFormLibrary.BaseForm
Since you want to change existing forms to inherit another base class you need to change each form that you want to take effect and change what they inherit.
Go to each of your forms designer code class. Inside towards the top you will see the inherits statment. Change what it inherits.
I am making an usercontrol with only one textbox so basically I expect that properties of textbox have to be applied to whole usercontrol.
That means (for example) that I would like from outside of usercontrol (in main program which contain those usercontrol) to get value of those (intern) textbox's selectionstart property.
But I can't find a way to do this except in creating a new public property of my UC.
I suppose that here should be some better way because textbox have many properties which may be needed to read (or maybe write) from main program and making another public property in UC for every internal property of textbox don't seems like "way to go" for me.
Any advice on how to get properties of internal control in UC from main program?
you may inherit your usercontrol from textbox control,liKe:
Class MyTextbox
inherits TextBox
End class
and then try to override, overload and access the events and properties you want.
you can check the following links,
1- For textbox inheritance example
2- Answered Question in Satckoverflow
Will not a regular FindControl check solve this?
I have two Forms, which have similar Functionality (i.e. an amount of similar Controls) but complete different Layout. So the normal inheritedForm (which VS2010 provides) wont work here.
I have tried following:
Public Class BaseForm
Inherits System.Windows.Forms.Form
Friend WithEvents Button1 As System.Windows.Forms.Button
End Class
And in Form1.Designer.vb:
Partial Class Form1
Inherits BaseForm
...
<all Designer generated Code>
...
' Friend WithEvents Button1 As System.Windows.Forms.Button <- remove this Line
End Class
If i compile/execute this, the test form works as expected; But now I am unable to design the form any longer.
If I switch to Design-Mode, it says:
The variable 'Button1' is either undeclared or was never assigned.
So it looks like, the Designer only tries to guess how the Form looks like by inspecting the top-most Class, without compiling the full inheritance-Tree...
Does anyone know a workaround for this?
Thx,
Daniel
I have a feeling you have some existing controls on the base form which you want to bring to the inherited form and then add more functionality of your own. Remember one thing, inheritance in VB.NET is by default set to shadowing, so you can redefine code in your inherited page for the same button to do a different function.
However, I think you forgot the Overridable keyword when declaring the form elements in the parent form. This will help the compiler know that the form can be overridden and allow you to define custom functionality.
Remember, all controls and pages in VB.NET are classes and whatever we learned during OOP classes in college apply here.
I am using visual inheritance and was wondering if there is a way to change the properties of inherited controls at design time, preferably in the form designer. If not, then in the designer code.
I have my control declared as Public in the base class. I can access it in the child form code, but not in the form designer. Is this just not possible?
There are limitations placed within visual studio for visual inheritance. Unfortunately, derived forms\usercontrols cannot modify controls containing collections within the base, namely DataGridViewRows, ToolStrips, ListViewColumns, etc.
Microsoft Bug Report
There are ways around this in certain situations. Create a protected property in the base class that exposes the exact properties of the control you wish to modify (DataGridView.BackgroundColor, or ListView.Columns).
Your base form should be able access this property to change the components needed. I've done this for ListView.Columns, and DataGridView.rows successfully, however ToolStrip.Items would not work.
It seems to work only for certain controls, but not all and I can't understand why. On my base form I have a TabControl that within it is a ComboBox, a ToolStrip, and a DataGridView. All of them are set to Public, but I can only modify the properties of the ComboBox and not the other two controls.
I have no idea why this is.
You need to change your control visibility. Put the control property Modifiers on public and recompile the project and then you can change properties of the inherited control.