VB.NET Properties
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Is it possible to force a property some how in VB.NET.(For a form) One way I could do this is to use a parameter in the constructor and delete the default constructor, but from what I have been told you are not supposed to modify the windows generated code. I am a noob with properties so any help would be appreciated. BTW the reason I am trying to do all of this is because if we do not have a parameter passed to this form when it is opened then it will not work properly and I would like to make it so that if we call this form without passing that property the compiler generates and error.
Humble Programmer
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Is it possible to force a property some how in VB.NET.(For a form) One way I could do this is to use a parameter in the constructor and delete the default constructor, but from what I have been told you are not supposed to modify the windows generated code. I am a noob with properties so any help would be appreciated. BTW the reason I am trying to do all of this is because if we do not have a parameter passed to this form when it is opened then it will not work properly and I would like to make it so that if we call this form without passing that property the compiler generates and error.
Humble Programmer
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You should look at the "New" sub. If you put code like the following, then everytime you create an instance the form, all parameters will be required: Public Sub New(Param as String) Blah Blah End Sub Does this work with forms? I think so.
Would this not be considered modifying windows generated code? Also the new is the constructor is that correct?
Humble Programmer
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Would this not be considered modifying windows generated code? Also the new is the constructor is that correct?
Humble Programmer
Yes, the New sub is the constructor. You are only adding an additional overloaded constructor which takes the parameters you need. If you want to ensure that only your contructor can be called (and not the default parameterless one) you can make the default constructor be a private function.
Scott Dorman
Microsoft® MVP - Visual C# | MCPD President - Tampa Bay IASA [Blog][Articles][Forum Guidelines]
Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai
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Yes, the New sub is the constructor. You are only adding an additional overloaded constructor which takes the parameters you need. If you want to ensure that only your contructor can be called (and not the default parameterless one) you can make the default constructor be a private function.
Scott Dorman
Microsoft® MVP - Visual C# | MCPD President - Tampa Bay IASA [Blog][Articles][Forum Guidelines]
Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai
But again would that not be modifying form generated code by changing the New sub to be Private?
Humble Programmer
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Is it possible to force a property some how in VB.NET.(For a form) One way I could do this is to use a parameter in the constructor and delete the default constructor, but from what I have been told you are not supposed to modify the windows generated code. I am a noob with properties so any help would be appreciated. BTW the reason I am trying to do all of this is because if we do not have a parameter passed to this form when it is opened then it will not work properly and I would like to make it so that if we call this form without passing that property the compiler generates and error.
Humble Programmer
Maybe I'm missing something. You're trying to create your own Form class, removing the New constructor that doesn't take any parameters, and adding another New constructor that does take a parameter?? Am I correct? You cannot remove the parameterless New method. Doing so will make the form unusable in the form designer since it will only create an instance of your form using the parameterless New method. OK, what's the property you're trying to "force" on this form??
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Dave Kreskowiak Microsoft MVP Visual Developer - Visual Basic
2006, 2007, 2008 -
But again would that not be modifying form generated code by changing the New sub to be Private?
Humble Programmer
No, it's not. There are also pitfalls do removing the New() method, as I've descrbied in my other post. The designer generated code sits in a #Region block specifically designated as "designer generated".
A guide to posting questions on CodeProject[^]
Dave Kreskowiak Microsoft MVP Visual Developer - Visual Basic
2006, 2007, 2008 -
But again would that not be modifying form generated code by changing the New sub to be Private?
Humble Programmer
As far as I can tell, when you create a new class that inherits from System.Windows.Forms.Form, Visual Studio will not automatically generate a default (parameterless) constructor in the code. The direct answer to your question is that, since the code does not already contain a default (parameterless) constructor, adding a new private default constructor is not changing generated code.
Scott Dorman
Microsoft® MVP - Visual C# | MCPD President - Tampa Bay IASA [Blog][Articles][Forum Guidelines]
Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai
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As far as I can tell, when you create a new class that inherits from System.Windows.Forms.Form, Visual Studio will not automatically generate a default (parameterless) constructor in the code. The direct answer to your question is that, since the code does not already contain a default (parameterless) constructor, adding a new private default constructor is not changing generated code.
Scott Dorman
Microsoft® MVP - Visual C# | MCPD President - Tampa Bay IASA [Blog][Articles][Forum Guidelines]
Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai
Whoops! My bad. [Edit] Actually, it's in the base Form class. But, you can't remove it if you want the form to show up in the designer. The designer uses only the parameterless constructor to create an instance of the form to show on the design surface. Removing it kills the ability to design the form.
A guide to posting questions on CodeProject[^]
Dave Kreskowiak Microsoft MVP Visual Developer - Visual Basic
2006, 2007, 2008 -
Maybe I'm missing something. You're trying to create your own Form class, removing the New constructor that doesn't take any parameters, and adding another New constructor that does take a parameter?? Am I correct? You cannot remove the parameterless New method. Doing so will make the form unusable in the form designer since it will only create an instance of your form using the parameterless New method. OK, what's the property you're trying to "force" on this form??
A guide to posting questions on CodeProject[^]
Dave Kreskowiak Microsoft MVP Visual Developer - Visual Basic
2006, 2007, 2008I have and existing form that calls another form which were both designed visually. I need to force a client number when calling this form or we cannot retrieve the correct information.
Humble Programmer
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Whoops! My bad. [Edit] Actually, it's in the base Form class. But, you can't remove it if you want the form to show up in the designer. The designer uses only the parameterless constructor to create an instance of the form to show on the design surface. Removing it kills the ability to design the form.
A guide to posting questions on CodeProject[^]
Dave Kreskowiak Microsoft MVP Visual Developer - Visual Basic
2006, 2007, 2008Hmmm...I actually created a blank VB WinForms project and didn't see any constructors, even in the designer generated file (Form1.Designer.vb). I do see it if I look at the compiled code with Reflector. Yes, I found that if I created my own private default constructor the code wouldn't compile, throwing errors in the Application.Designer.vb file.
Scott Dorman
Microsoft® MVP - Visual C# | MCPD President - Tampa Bay IASA [Blog][Articles][Forum Guidelines]
Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai
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I have and existing form that calls another form which were both designed visually. I need to force a client number when calling this form or we cannot retrieve the correct information.
Humble Programmer
Simply create a instance variable and a parameter in the form class:
Private _clientNumber as Integer
Public Property ClientNumber() As Integer
Get
Return _clientNumber
End Get
Set(ByVal Value As Integer)
_clientNumber = Value
End Set
End PropertyAfter you instantiate the form, but before you display it, set this value in the calling code. Then use the value stored in the property when you show the form.
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Simply create a instance variable and a parameter in the form class:
Private _clientNumber as Integer
Public Property ClientNumber() As Integer
Get
Return _clientNumber
End Get
Set(ByVal Value As Integer)
_clientNumber = Value
End Set
End PropertyAfter you instantiate the form, but before you display it, set this value in the calling code. Then use the value stored in the property when you show the form.
This is actually what we are doing now. What I want to know is there any way that you can say if that does not have a value when the form is shown don't compile throw a compile time error. Like if you did remove the New Sub and made your own with parameters and when you called the class you did not supply the parameter it would blow up.
Humble Programmer
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This is actually what we are doing now. What I want to know is there any way that you can say if that does not have a value when the form is shown don't compile throw a compile time error. Like if you did remove the New Sub and made your own with parameters and when you called the class you did not supply the parameter it would blow up.
Humble Programmer
programmer_vb.net_c++ wrote:
What I want to know is there any way that you can say if that does not have a value when the form is shown don't compile throw a compile time error.
Not correctly, no. You would check something like this at runtime, not design time. You'd throw an exception if the proper values were not in place.
A guide to posting questions on CodeProject[^]
Dave Kreskowiak Microsoft MVP Visual Developer - Visual Basic
2006, 2007, 2008 -
Hmmm...I actually created a blank VB WinForms project and didn't see any constructors, even in the designer generated file (Form1.Designer.vb). I do see it if I look at the compiled code with Reflector. Yes, I found that if I created my own private default constructor the code wouldn't compile, throwing errors in the Application.Designer.vb file.
Scott Dorman
Microsoft® MVP - Visual C# | MCPD President - Tampa Bay IASA [Blog][Articles][Forum Guidelines]
Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai
Scott Dorman wrote:
Hmmm...I actually created a blank VB WinForms project and didn't see any constructors, even in the designer generated file (Form1.Designer.vb).
I already correct my mistake. It's not in the designer generated file. It's in the base Form class that your Form1 class is inheriting from.
A guide to posting questions on CodeProject[^]
Dave Kreskowiak Microsoft MVP Visual Developer - Visual Basic
2006, 2007, 2008