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.NET Forum / Windows Forms / Design Time / December 2005How cancel a Copy operation?
Good morning this is the code I use in a container control designer to prevent that another control (any) is copied directly inside him: Public Overloads Overrides Function CanParent(ByVal aControl As Control) As Boolean Throw New Exception("Adding an item directly to the CommandBar is not allowed.") Return False End Function This code works, but after the exception is raised and the newly created control is not added to the container, the newly created control is *added* to the the parent Form and becomes unused (dead). This means that an instance of the new control is created in the 'ctor of the form (inside "Windows Form Designer generated code"). How to avoid this? Thank you very much Carlo ------------------------------------------- Carlo, MCP (Windows Based Applications) carlodevREMOVE@gmail.com Hi Carlo, Il Thu, 22 Dec 2005 09:59:03 +0100 hai scritto : > Good morning > this is the code I use in a container control designer to prevent that > another control (any) is copied directly inside him: > Public Overloads Overrides Function CanParent(ByVal aControl As > Control) As Boolean > Throw New Exception("Adding an item directly to the CommandBar is > not allowed.") > Return False > End Function > This code works, but after the exception is raised and the newly > created control is not added to the container, the newly created control > is > *added* to the the parent Form and becomes unused (dead). > This means that an instance of the new control is created in the 'ctor > of the form (inside "Windows Form Designer generated code"). > How to avoid this? I have not done any test with our code but I ususally behave in this way: a) simply return "false" in the override of CanParent method, this method is called by the designer during drag operations (of "form's" control only) and is used to determin if the dragged item can be dropped to the target, this method is not called during drag operations from the "ToolBox", don't know why but that is... b) Create a new class inheriting from Control.ControlCollection (eg MyControlsCollection), override the Add() method and test here if the incoming control can be added (if true add it to the "base" class) to your control controls collection otherwise throw an exception... ArgumentException shuold be the best choice in this case c) in your control override the CreateControlsInstance() protected method and return a new instance of the newly created "MyControlsCollection" class. CreateControlsInstance() is called once when the control need to access for the first time his controls collection In my scenarios these solutions works fine for cut&paste/copy&paste operations, let us know... > Thank you very much > Carlo HTH, Mauro Servienti whynot [ at ] topics [ dot ] it -- "...voi abili a tenere sempre un piede qua e uno là avrete un avvenire certo in questo mondo qua però la dignità dove l'avete persa?..." "Vasco Rossi - Gli Spari Sopra (1993)" Hello Mauro. I fear I was not enough clear explaining my problem. I'll try once more, trying to be me more clear... Assume you have a simple control (MyControl), with no properties or methods, hidden to the IDE Toolbox and finally with just an attached designer. The designer has only these lines: Public Overloads Overrides Function CanParent(ByVal aControl As Control) As Boolean Throw New Exception("Adding an item directly to the CommandBar is not allowed.") Return False End Sub Your goal is to manage MyControl via code only, instead via the IDE designer. To reach this, you need to prohibit to the user to Copy an existing MyControl and Paste it again into the form or into a generic container. In the real life, MyControl is part of another control's collection (a Toolbar), but this is irrilevant, you only need to prevent MyControl to be copied everywhere. Now: if you click any MyControl on a form, Ctrl-C and then Ctrl-V, you get a "Adding an item directly to the CommandBar is not allowed" message and your copy is correctly aborted. But, if you are very curious and go to snoop inside "Windows Form Designer generated code" region, you will find a never-used instance of the newly Ctrl-C(opied) control. This is just what I need to avoid: a dead instance of MyControl. Please, accept my best wishes for a Merry Christmes and a very happy new year, extended to your family! Sincerely, Carlo ------------------------------------------- Carlo, MCP (Windows Based Applications) carlodevREMOVE@gmail.com > Hi Carlo, > [quoted text clipped - 53 lines] > certo in questo mondo qua però la dignità dove l'avete persa?..." > "Vasco Rossi - Gli Spari Sopra (1993)" Sorry, previous post was wrong. The following is correct: ----------------------------------------- Hello Mauro. I fear I was not enough clear explaining my problem. I'll try once more, trying to be me more clear... Assume you have a simple control (MyControl), with no properties or methods, hidden to the IDE Toolbox and a very simple container with just an attached designer. The container's designer has only these lines: Public Overloads Overrides Function CanParent(ByVal aControl As Control) As Boolean Throw New Exception("Adding an item directly to the CommandBar is not allowed.") Return False End Sub Your goal is to manage MyControl via code only, instead that via the IDE designer. To reach this, you need to prohibit to the user to Copy an existing MyControl and Paste it again into the container. In the real life, MyControl is part of container's controls collection (a Toolbar), but this is irrilevant, you only need to prevent a standalone instance of MyControl to be copied to the container. Now: if you click any MyControl on a container, Ctrl-C and then Ctrl-V, you get a "Adding an item directly to the CommandBar is not allowed" message and your copy is correctly aborted. But, if you are very curious and go to snoop inside "Windows Form Designer generated code" region, you will find a never-used instance of the newly Ctrl-C(opied) control. This is just what I need to avoid: a dead instance of MyControl. Please, accept my best wishes for a Merry Christmas and a very happy new year, extended to your family! Sincerely, Carlo ------------------------------------------- Carlo, MCP (Windows Based Applications) carlodevREMOVE@gmail.com > Hi Carlo, > [quoted text clipped - 53 lines] > certo in questo mondo qua però la dignità dove l'avete persa?..." > "Vasco Rossi - Gli Spari Sopra (1993)" Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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