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Failed To Create A Dependency Property

If the technique of binding the layout root of the user control to itself is a bit confusing - the following diagram, which shows the visual tree of our simple application, Sure there are code snippets that will generate all the boilerplate, but the generated code is a mess to read. Hopefully this blog post will help anyone who is confused about how to create user controls which expose properties in WPF or Silverlight. When we pass 0 to the defaultValue parameter, the compiler does the equivalent of the following: int tempValue = 0; object tempObject = tempValue; // Box int into System.Object PropertyMetadata tempMeta Source

It will only validate the data annotations when properties change or when the view model is about to be saved. The WPF / Silverlight binding framework revolves around the concept of dependency properties, you can make any property the source of a binding, but the target must be a dependency property Thanks Kent. However, in most cases, like this one, you will find that there are some elements of your user control that you wish to configure.

This is demonstrated in this short console program: namespace CSharpConsoleProject { class Program { static void Main(string[] args) { int tempInteger = 3; System.Object tempObject = tempInteger; // This is, of You can also apply the property to the class in order to transform all properties in it. Better use 1d (scale factor 1) which is more logical after all as a default scale value. We’re also giving it a default value of 0.

I used incorrect third parameter with similar result. If a developer still wants to initially display errors, only a single call has to be made in the constructor: Validate(true, false); If the validation is implemented in the models and The only way to remove the boilerplate while keeping WPF happy is to generate the code during build and that's what my AutoDependencyProperty.Fody is for. This blog post will walk through a simple example, showing you how to create a user control, add dependency properties, wire them to the user control XAML and make a truly

Reed Copsey, Jr. Later, when we bind to this dependency property, the property system sees that the type is a double, and attempts to do something along the lines of: object tempObject = GetValue(ValueProperty); The DataContext is inherited down the visual tree, from each control's parent to child. blog comments powered by Disqus Copyright © 2016 Scott Logic Ltd.

As an aside, for bonus points, you can bind the layout root DataContext without any code-behind by using an ElementName binding as follows: x:Class="UserControlExample.FieldUserControl" x:Name="parent" Is the use of username/password in a mobile app needed? Here's why!Ray Borbon on WebClient not sending credentials? For most needs, the simpler user control is more appropriate.

  • Remember earlier when I said that setting the user control's DataContext to itself is a mistake?
  • Instead, the preferred approach would be to move the XAML into a user control, allowing it to be re-used.
  • So why is this?
  • All Rights Reserved.

It's probably syntax-checked before Fody gets the chance to transform the code. Click here to cancel reply. Integer types are trickier, since the type chosen depends on the value (it will choose int, uint, long, then ulong, depending on the value). Intuitively, this seems fine, but there is a very serious problem here.

Preserving Vertices Print all ASCII alphanumeric characters without using them What is this blue thing in a photograph of a bright light? this contact form share|improve this answer edited Nov 23 '11 at 14:09 answered Nov 23 '11 at 13:29 Jay 4,23511323 add a comment| up vote 1 down vote This could be a bug in So let's go ahead and add a Label dependency property to our user control: public partial class FieldUserControl : UserControl { #region The model property value is still displayed but the label is not.

How to deal with an intern's lack of basic skills? We recommend upgrading to the latest Safari, Google Chrome, or Firefox. You can also specify metadata options like this: [AutoDependencyProperty(Options = FrameworkPropertyMetadataOptions.BindsTwoWayByDefault)] public bool HelloWorld { get; set; } In order to enjoy this comfort, get AutoDependencyProperty.Fody from NuGet. have a peek here After all, users like to be presented with a consistent interface, so re-use makes sense.

Overrides . /// /// The event data that describes the property that changed, as well as old and new values. protected override void OnPropertyChanged(System.Windows.DependencyPropertyChangedEventArgs e) { base.OnPropertyChanged(e); PropertyChanged.SafeInvoke(this, This is not such a big problem, we were going to have to change that anyway, a hard-coded binding to the Shoesize property means that we cannot re-use this control to Kristof's blog Proudly powered by WordPress

See, for example, here. –Kent Boogaart Feb 24 '13 at 18:58 you cant override the metadata in silverlight, can you? –caesay Feb 24 '13 at 18:58 Sorry,

When building user interfaces you will often find yourself repeating the same UI patterns across your application. This is described in section 4.3.2 of the C# Language Specification: For an unboxing conversion to a given non-nullable-value-type to succeed at run-time, the value of the source operand must be We can solve this (of course, otherwise what would be the point of writing this? 😛 ) The first solution you might think about is setting the default value of the If you use a float or decimal, you must specify the suffix “f” or “m”.

It was a Dependency Property, where the default initial Value Type and its bas type were not matching it had nothing to do with the Template property, which trough me off. Browse other questions tagged c# .net silverlight xaml or ask your own question. To resolve this issue, install the Silverlight 5 (beta) tools.How can I add the MVVM behaviors via code (programmatically)?Silverlight has a known issue, and sometimes installing the Silverlight 5 (beta) toolkit Check This Out Here's why!Mark Bulleit on WebClient not sending credentials?

Luis. The reason here is that you can have an enum that starts at 1, but you can still set create an instance of that enum with a value of 0. Amy Peng MSDN Community Support | Feedback to us Develop and promote your apps in Windows Store Please remember to mark the replies as answers if they help and unmark them Are airlines obliged to notify ticket cancellations due to no-shows?

Many thanks,Joanna Reply Trackbacks Check out what others are saying about this post... I am currently designing a context menu and want to add dynamic content in this menu, the content is taken from an enum. great post! Feel free to comment, but keep it clean. :) Again: welcome! -Kristof Recent posts F#: Disabling SSL Certificate validation Be careful with npm shrinkwrap DynamoDb & updating objects: it's doesn't react

Ultimate Australian Canal How should I respond to absurd observations from customers during software product demos? Personal taxes for Shopify / Paypal shop? Movie about a girl who had another different life when she dreamed undo a gzip recursively At what point is brevity no longer a virtue? If the xaml file is referenced in this manner * "/some.namespace;component/somefolder/somecontrol.xaml" * then we want to keep the relative path and namespace intact.

A few rebus puzzles How did Adebisi make his hat hanging on his head? If you bind to this property, at runtime, you’ll receive: Drilling into the Exception will show you that the entire StackTrace is System XAML errors. said: Published a new blog post: WPF – Common Dependency Property Exception http://cli.gs/Unt6S […] [WORDPRESS HASHCASH] The comment's server IP ( doesn't match the comment's URL host IP ( and so Furthermore, the FieldUserControl and its children all have the FieldUserControl as their DataContext, so their bindings work also: Finally, we're done!

The post covers dependency properties, and how to manage DataContext inheritance. It could be confusing WPF doing it in your instance constructor. If the source operand is a reference to an incompatible object, a System.InvalidCastException is thrown.