I am a beginner of MVVM. I wanted to bind selected treeview item to a textblock. I found a solution here. So I implemented the same in my project...:
<TextBox Text="{Binding SelectedItem, Converter={StaticResource GetTextFromItemConverter}, ElementName=tvMain, Mode=OneWay}"
Also created the GetTextFromItemConverter class in my viewmodel(same as in the solution).
But in xaml I got error saying
The resource GetTextFromItemConverter could not be resolved.
How to resolve this issue??
I suppose the class GetTextFromItemConverter is defined in some namespace called TestDemo. You first have to create some instance of that class as some resource in XAML. As an example, you can add it as some resource of Window.Resources, we need to import the namespace of that class so that we can create an instance of that class, something like this:
<Window ...
xmlns:local="clr-namespace:TestDemo">
<Window.Resources>
<local:GetTextFromItemConverter x:Key="textConverter"/>
</Window.Resources>
<!-- ... -->
<TextBox Text="{Binding SelectedItem,
Converter={StaticResource textConverter},
ElementName=tvMain, Mode=OneWay}"/>
<!-- ... -->
</Window>
Note about the added part xmlns:local="clr-namespace:TestDemo" is to import the TestDemo namespace and aliased as local prefix. The ... is a placeholder for what you have in your Window (auto-generated by designer).
Check whether the view model that you have mapped is properly referenced, if so its perfect check for the path reference to the converter that you have used.
For example:
xmlns:converter="using your namespace path"-location where the converter is placed in the resource dictionary.
Related
I'm trying to use the PropertyGrid component from PropertyTools to display information on an object. I can bind the object easily enough -- it's a property on my DataContext -- but one of the things that can't be derived from the object is the name that should be displayed in the tab header. (And I can't change that; the object I'm inspecting comes from a third party.) The proper name is a different property on my DataContext.
PropertyGrid has a way to change the way the tab header is displayed, by passing a DataTemplate to its TabHeaderTemplate property. But something bizarre happens inside of the template: my DataContext is gone, replaced by something else. When I try to say {Binding TabName} in the appropriate place inside the context, it errors out and tells me that TabName is not a valid property on class Tab. But my DataContext class isn't called Tab; that's something inside of PropertyTools's codebase!
I'm still new to WPF, so I have no clue what's going on here. Why is the in-scope DataContext that's perfectly valid in the rest of the XAML file being yoinked out from under me inside this template, and how can I fix it?
EDIT: Posting the XAML as requested. The template is literally just the simplest possible thing:
<UserControl.Resources>
<DataTemplate x:Key="HeaderTemplate">
<TextBlock Text="{Binding TabName}" />
</DataTemplate>
</UserControl.Resources>
And then further down the page,
<props:PropertyGrid
SelectedObject="{Binding Value}"
TabHeaderTemplate="{StaticResource HeaderTemplate}" />
But for some bizarre reason, in the template it's trying to interpret the binding inside the wrong DataContext!
In this case, just be sure to specify the source in your binding. There are a few ways to do this. One is to use the RelativeSource property of the Binding. Another is to use ElementName
Give your UserControl this attribute:
x:Name="Root".
Then change your binding to use it
<TextBlock Text="{Binding ElementName=Root, Path=DataContext.TabName}" />
Or use this:
<TextBlock Text="{Binding RelativeSource={RelativeSource AncestorType={x:Type local:MyUserControl}}, Path=DataContext.TabName}"/>
I have a grid that I am trying to hook up a visibility converter to. I have a class set up in the HelperObjects namespace, but for some reason the xaml is not picking up the reference. The error message is "The resource BoolToVisConverter could not be resolved" Why won't the xaml pull in this resource? I am sure I am doing something ridiculous here...
Here is the xaml:
xmlns:HelperObjects="clr-namespace:foo.HelperObjects"
...
<Grid Visibility="{Binding isZoneTwoVisible, Converter={StaticResource BoolToVisConverter}}">
The error message is indicating that the resource identified by the key BoolToVisConverter, to which you're trying to bind, cannot be found.
The most likely explanation is that you haven't declared that resource within a scope that can be accessed by your xaml. You'll want to create a StaticResource with a key matching the name you're referencing, within a Resources section of your xaml, the exact location may vary depending on your needs/structure.
Assuming you're doing this within a Window, you could do something like:
<Window>
<Window.Resources>
<BooleanToVisibilityConverter x:Key="BoolToVis"/>
</Window.Resources>
<Grid Visibility="{Binding isZoneTwoVisible, Converter={StaticResource BoolToVis}}">
<--...Content...-->
</Grid>
</Window>
Note: I haven't included your namespace in front of the BooleanToVisibilityConverter because this is a class which already exists within the framework.
It may be the case you require slightly different behaviour, or don't have access to that class, in which case you may need to add your namespace when defining the resource, e.g. <HelperObjects:BooleanToVisibilityConverter x:Key="BoolToVis"/>
Potentially useful further info about static resources: https://learn.microsoft.com/en-us/dotnet/framework/wpf/advanced/staticresource-markup-extension
Try to specify the converter in UserControlResources or even parent level Grid Resources. Assuming you are using a UserControl.
And your code is unclear as of where you are defining the StaticResource BoolToVisConverter. But generally heres the process.
Look at this sample code below to define your StaticResorce in the UserControl Resources section. Make sure you set the DataContext where isZoneTwoVisible is residing. I am hoping you implemented ImplementINotifyPropertyChanged and said PropertyChanged on your isZoneTwoVisible or isZoneTwoVisible is a DependencyProperty. Note: BooleanToVisibilityConverter is a class that implements an IValueConverter or if your property is a bool you don't even need that class.
<UserControl.Resources>
<BooleanToVisibilityConverter
x:Key="boolToVisibility"></BooleanToVisibilityConverter>
</UserControl.Resources>
You did all the things said above and it still dosen't work, sometimes I specify the relative Source hoping its residing in a UserControl.
Visibility="{Binding isZoneTwoVisible,Converter={StaticResource boolToVisibility},RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=UserControl}}">
I have a binding to a parent-element. How can I provide the data type for the DataContext in the binding, so intellisense can resolve the bound Properties?
The binding works fine at runtime. So, I have the following XAML structure:
<TabControl Name="TabDynamic"
ItemsSource="{Binding TabItems, Mode=OneWay}" ...>
<TabControl.Resources>
<DataTemplate x:Key="TabHeader" DataType="TabItem">
<DockPanel>
<TextBlock Text="{Binding RelativeSource={RelativeSource AncestorType={x:Type TabItem}}, Path=Header}" />
<Button Command="{Binding ElementName=TabDynamic, Path=DataContext.DeleteTabCommand}"
CommandParameter="{Binding ElementName=TabDynamic, Path=DataContext.TabItems/}">
<Image Source="{DynamicResource DeleteImg}" Height="11" Width="11"></Image>
</Button>
</DockPanel>
</DataTemplate>
<DataTemplate x:Key="TabContent" DataType="viewModels:ConnectionInfoVM">
<views:BufferViewerControl/>
</DataTemplate>
</TabControl.Resources>
</TabControl>
The data type of the DataContext is "viewModels:ConnectionInfoVM".
Intellisense will now underline both Properties on the DataContext (so DeleteTabCommand and TabItems are underlined).
I already tried to use the design-time data-context definition "d:DataContext" within the Button element like so:
d:DataContext="{d:DesignInstance viewModels:ConnectionInfosVM}"
But this does not change the intellisense warnings.
I also tried to define the DataType on the DataTemplate to be "viewModels:ConnectionInfosVM", as I do for the content-template, but that too does not change the intellisense warnings (and I guess would be wrong, as the data type of the element really is a TabItem).
Another try was to define the DataContext by adding the following to the Button element definition:
<Button.DataContext>
<viewModels:ConnectionInfosVM/>
</Button.DataContext>
But this too, does not get rid of the warnings.
I found a solution at least for the above described problem. I was setting the DataContext of the window in question in the code-behind. The TabControl in my example just inherits that DataContext, which is a ConnectionInfosVM.
In order to fix those warnings (and of course for the gained flexibility in providing a DataContext by a Locator), I defined the DataContext in XAML like so:
<UserControl ...
DataContext="{Binding Source={StaticResource mainViewModelLocator}, Path=ConnectionInfosVM}">
It seems that intellisense is now able to resolve those references. But on the other side, I also changed the TextBlock contained within the DataTemplate to the following:
<TextBlock Text="{Binding RelativeSource={RelativeSource AncestorType={x:Type TabItem}}, Path=DataContext.Address}" />
Now the DataContext of such a TabItem is actually a different type, as it is the type of the backing object for the TabItem. So in this case, the Property Address cannot be found by intellisense.
So, the question kind of remains, is there a possibility to define the type of the DataContext within a binding defined in a DataTemplate?
I needed to add the mc:Ignorable="d" attribute to the Window tag. Essentially I learned something new. The d: namespace prefix that Expression Blend/Visual Studio designer acknowledges is actually ignored/"commented out" by the real compiler/xaml parser!
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
The following was taken from
Nathan, Adam (2010-06-04). WPF 4 Unleashed (Kindle Locations 1799-1811). Sams. Kindle Edition.
Markup Compatibility
The markup compatibility XML namespace (http://schemas.openxmlformats.org/markup-compatibility/2006, typically used with an mc prefix) contains an Ignorable attribute that instructs XAML processors to ignore all elements/attributes in specified namespaces if they can’t be resolved to their .NET types/members. (The namespace also has a ProcessContent attribute that overrides Ignorable for specific types inside the ignored namespaces.)
Expression Blend takes advantage of this feature to do things like add design-time properties to XAML content that can be ignored at runtime.
mc:Ignorable can be given a space-delimited list of namespaces, and mc:ProcessContent can be given a space-delimited list of elements. When XamlXmlReader encounters ignorable content that can’t be resolved, it doesn’t report any nodes for it. If the ignorable content can be resolved, it will be reported normally. So consumers don’t need to do anything special to handle markup compatibility correctly.
I am trying the following in my WPF application:
Structure of XAML elements.
DataTemplate[Data Type 'A']
Grid
Broder
TextBlock
I want to bind the text block's text property to a "string" which is derived from my "Users" class which is referenced in the resource dictionary of the XAML.
So in the above structure since the DataTemplate gets the feed from data type 'A'.
I want to assign the datacontext(Users) to the grid and bind the string to the textblock.
Is there a way i can achieve this ,since all my trials which include assigning the datacontext to the Grid or Border or TextBlock doesn't work.
Can any one suggest me or correct me if my approach is wrong here ?
This markup should suffice:
<DataTemplate DataType="{x:Type local:A}">
<Grid DataContext="{Binding Path=Users}">
<Border>
<TextBlock Text="{Binding Path=PropertyOnUsers}"/>
</Border>
</Grid>
</DataTemplate>
Make sure you have the namespace declared at the top of your Xaml. For whatever reason, WPF doesn't always automatically infer the template from the type if you don't use {x:Type ...}.
From there it should be straight forward.
If Users is a collection, you will have to drill into the collection to get a specific instance of User.
By the way, if you are using Visual Studio, you can use the Output window to debug binding issues.
How can I change the Text of a TextBlock when the selection in my ListView changes?
I don't want do this manually...
All Items of the ListView are LogEntry's (class)... Can I use Binding in the Text-Attribute of the TextBlock to get a specific property of the selected Item?
Yes, in fact there are multiple solutions, i give you the most "WPF" like answer, but imo also the least flexible.
First you need to set the IsSynchronizedWithCurrentItem="True" property
Now if you select an item, the bound CollectionView will set the item as the CurrentItem.
Now your TextBox/Block can bind to this specific item via a special binding syntax using a '/'.
For Example:
<TextBlock Text="{Binding LogEntries/}"/>
of course you can get a specific property from the current item via binding aswell
<TextBlock Text="{Binding LogEntries/WarningMessage}"/>
Hope that helps.
assuming you have a listview like this:
<ListView ItemSource="{Binding LogEntries}" Name="logs" IsSynchronizedWithCurrentItem="True">
</ListView>
<ContentControl Content="{Binding ElementName=logs, Path=SelectedItem}" ContentTemplate="{StaticResource logTemplate}"/>
Now you need to provide that logTemplate in the Resources.
<UserControl.Resources>
<DataTemplate DataType="{x:Type local:LogEntry}">
<TextBlock Text="{Binding Path=LogText}"/> <-- This is a Property-Binding of your custom class
</DataTemplate>
</UserControl.Resources>
The last thing missing is to provide the namespace to your local class LogEntry. If you use an awesome tool like Resharper, it will insert the namespace for you. Otherwise, here a sample declaration:
<UserControl xmlns:local="clr-namespace:My.App.Namespace.LogEntry;assembly=My.App"
... (rest of namespace declarations)