After several days of happily hacking away on this C# app using Visual Studio 2008, I get struck by a barrage of error dialogs showing:
Code generation for property 'valueMember' failed.
Error was: 'Object reference not set to an instance of an object.'
This happens now often when I make a tiny change in the designer, e.g. shift a control a few pixels, and then try to save. Several such error dialogs appear each second, keeping me busy cancelling all those by hammering the Enter key while trying to get alt-F4 to get VS to close.
Eventually I do get VS to close and to save the changes I made. After restarting VS, I do "clean" on the entire project, then "build" and everything works fine, the app runs fine, no problems.
Until I make another slight change in the form designer.
I don't know about any property valueMember in my app.
This makes me crazy, it is a real showstopper for my project. Any help is appreciated.
Try to Close and reopen the Visual Studio. maybe it seem silly, but it works!!
You can debug the designer using another visual studio and attach to process. If you got exception it should be easy to find it that way.
In general when openning the designer the constructor and of course initializeComponent is running.
As this is happening at design time, it is likely that you have a custom control which requires a parameter or other value which does not have a default.
When in design view in Visual Studio; a control instance is created to render it on the visual editor, but if the control requires a property to be set before it can be rendered, it will result in an error.
Can you check that all custom controls have default values, and anything referenced in the constructor that cannot have a default is wrapped by DesignMode property - see http://msdn.microsoft.com/en-us/library/system.componentmodel.component.designmode.aspx.
Similiar to #Chanipoz's answer (close/re-open) my component-rich/user-controls-everywhere forms app started to compile happily after I closed down the main form designer window.
I've had this code stack for years and have never seen the error until today. Not sure where it's coming from. But, something today about having the form open in the designer made everything unhappy. Simply closing it off of the screen made it all go smooth.
Use another instance of Visual Studio to attach to the first instance of visual studio.
Go to Debug-> Attach To Process and look for the devenv.exe process. Since you'll have two devenv.exe processes running you'll probably want to pick the one with the lower ID, that's usually the first instance of visual studio that was run.
I had to face this problem. As I have found the solution below
I am facing this issue in my customized control.
we need to implement like this
[Browsable(false)]
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
public MyCustomclass _Prperty { get; set; }
I had to face this problem. As I have not found the solution (much inheritance), I can tell:
.SuspendLayout() and .ResumeLayout() may be missing in code or one of them. The same is with .BeginInit() and .EndInit(). It is expected between them, that there will be = new ... and some settings for properties. Maybe someone facing this problem would find the solution with this information.
The problem is missing initialization code for a public property on the control. This will be added for you when you add the control to the designer, but if you replace a control with a derived control, or update the component, then the designer does not know how to deal with this.
If you have a control (wincontrol) with a public property PropertyA, and you add it to a form (myForm), then the designer will add all the necessary initialization for properties into myForm.Designer.cs. Something like;
Wincontrol1.PropertyA = new List<widget>();
It is not uncommon to need to modify a control slightly, lets say we have a new control MyWinControl
public partial class MyWinControl : WinControl
{
public List<wodget> PropertyDer1;
protected List<wodget> PropertyDer2;
}
If you sub this new control for the old control in myForm.Designer.cs, then you may well encounter this issue. The reason is that PropertyDer1 has no initialization in the winforms designer. PropertyDer2 won't cause any issues because it is protected. Similarly if you had a custom component and you add a new public property after the component has been added to a form.
If however, you deleted the instance of WinControl on the form, and dragged an instance of the MyWinControl onto the form instead, the proper initialization would occur and you would not see the error. The designer will have created the new control like this
Wincontrol1.PropertyA = new List<widget>();
Wincontrol1.PropertyDer1= new List<wodget>();
There are two easy solutions that do not require hiding the property from the designer.
1. If the property doesn't need to be public, give it the right modifier
2. If the property does need to be public, then just edit the code in the myForm.Designer.cs as in the code above to add the missing initializer
If could be of help I just detected a case that brings that same error message, impossible to take away :
I am developing an application in French, and I had to create a ToolStripMenuItem with an accented word in it like "annulées".
The system generated a menu item like "annuléesToolStripMenuItem" and the accent is the culprit.
Enough to delete the item, create it again in English and the just change the Text property of the menu item.
Hope it will be of some help.
I just finished adding and removing different database models (I was trying to figure out which one I should be using for this project) then after playing around for a while I noticed one of my classes's icon changed from what is shows beside my Calculations.cs class in the first image to the Balance.cs icon.
The Balance.cs now has this Designer component so when I double click on it I see my second screen shot. This seems to be allowing me to add components from the toolbox to my class. There are actually two classes within my Balance.cs. This Designer thing is only affecting/interacting with one of them (it inherits from SerialPort).
I don't really know what changed or what I did to make this happen and ctrl+z is not being my friend here. How do I change Balance.cs back to a regular class with no designer component?
Thanks
If any of the classes in a source file inherit - either directly or indirectly - from System.ComponentModel.Component (such as SerialPort), Visual Studio will provide design-time support to you. This is sometimes unwanted behaviour, and you can safely ignore it in most cases.
If it really bothers you, you can decorate your class with the [DesignerCategory] attribute (set the category to an empty string).
Is there a way to see controls which are created via code in designer instantly but not only during execution?
The Windows Forms designer only applies properties contained in the automatically generated file "Form1.Designer.cs" (example filename for "Form1"). If you change properties (e.g. text, color, whatever) or create new controls in your own code, i.e. in "Form1.cs", the designer does not show it.
It is practically impossible because the designer would have to either 1) parse your code or 2) execute it to apply all changes to the controls.
Option 1 does not work because expression evaluation only works when running the code... Which leads us to option 2: Letting the designer running your code to find out dynamically added properties? First of all, automatically running untrusted code is not what you want. Second, there must be a reason that you do these changes dynamically instead of statically in the designer, so showing dynamic changes as WYSIWYG does not even make sense.
The designer can only display controls that exist at design time or show example controls for databound controls. If you think about code that would dynamically at runtime create a textbox or label based on a variable, how would the designer know which one to display in design mode?
If you have specific logic for how you want your dynamically created controls to display in design mode, you would have to create a custom control and implement the design time drawing code. This is mentioned under the Custom Design Experience heading here: http://msdn.microsoft.com/en-us/library/ms171725.aspx
I am attempting to create a CustomControl in C# which contains a Delphi TFrame, which can be dragged from the VisualStudio toolbox onto a Form. This much I have working correctly, however when I attempt to resize the control errors occur due to the TFrame not running in design mode (it attempts to access the event handlers for a data grid on the frame).
I have created a TFrame object in Delphi which contains various controls (data grid, combobox etc), and a CustomControl in C# which contains the TFrame object.
To get around this problem I think I need to set the Site property of the TFrame object, so that DesignMode is true. How can I go about doing this?
I know I can get around this problem by checking at the start of each method if the LicenseManager.UsageMode is set to DesignTime, but this seems a very bad way of solving the problem. So if possible I would like to get the site property set correctly.
I am using CodeGear RAD Studio 2007 and Visual Studio 2008.
Thanks in advance
Turns out this problem is caused by a bug within Visual Studio where the DesignMode and Site property never gets set on components created within a constructor or a UserControl. Therefore the DesignMode property is always false.
There are several proposed solutions all of them involve adding a test to any event handlers or methods where code should only be executed at runtime. The first option is to check the LicenseManager.UsageMode property, and the second option is to check the name of the executing process (e.g. if its "devenv" then its design time).
I had this answer on another post I asked:
"I believe the VS designer does it [components of a menustrip/statusstrip] by getting an instance of the control's designer (see the Designer attribute), and, if the designer is a ComponentDesigner, getting the AssociatedComponents property."
How do I do this? I'm not even sure where to begin...
The DesignerAttribute attribute can be attached to a Control or Component class in WinForms to indicate the class that implements a designer for visually editing that type of control or component. For example, the Form class has a DesignerAttribute that indicates a class called FormDocumentDesigner implements its designer.
Designers allow special design-time behavior to be applied in the WinForms designer in Visual Studio such as list view column resizing or the sizing handles on controls. Designers that support the addition of child controls to an existing control, such as FormDocumentDesigner are ultimately derived from ComponentDesigner.
You can check this out by using a tool like .NET Reflector.