<DatePicker Date="date" Format="d MMM yyyy" HorizontalOptions="EndAndExpand" x:Name="date"/>
By having that line of code in my xaml code. how can i set the date to NOW when i create a new data?
You can either change the Date attribute to something like this: Date="{Binding MyDate}" and then in your code-behind assign a view model to the BindingContext property. For example:
public class MyViewModel
{
public DateTime MyDate { get; set; }
}
and in your page:
public class MyPage
{
public MyPage()
{
InitializeComponent();
var viewModel = new MyViewModel();
viewModel = DateTime.Now;
BindingContext = viewModel;
}
}
Or, if you don't need to use a view model or MVVM (which I would highly recommend), you can just set it directly from your code-behind. Because you gave the DatePicker an x:Name attribute, you can refer to it by that name.
public class MyPage
{
public MyPage()
{
InitializeComponent();
date.Date = DateTime.Now;
}
}
You can define it in two ways
Using the "x:Name" you can define the date in XAML.cs.
Using the Binding property for "Date" you can define the date in ViewModel class
In your case in xaml.cs
date.Date = DateTime.Now;
Related
i am trying to bind my MasterViewModel where i have initiated two original viewModel to one view. But i am not getting any data so i must be doing the binding wrong. I have found several post
I have tried
in Xaml
<Label
x:Name="SectionRequired"
Grid.Row="2"
HorizontalOptions="End"
IsVisible="{Binding PostViewModel.IsRequired, Source={x:Reference PostViewModel}}"
Text="{x:Static resources:AppResources.AlertRequired}"
TextColor="Red" />
And also followed this solution but i was getting an expcetion that its used lika markup extenstion 'local1:PostViewModel' is used like a markup extension but does not derive from MarkupExtension.
https://stackoverflow.com/questions/50307356/multiple-bindingcontexts-on-same-contentpage-two-different-views
My Master
class MasterPostsViewModel : BaseViewModel
{
public PostViewModel postViewModel { get; set; }
public CategoriesViewModel categoriesViewModel { get; set; }
public MasterPostsViewModel()
{
postViewModel = new PostViewModel();
categoriesViewModel = new CategoriesViewModel();
}
}
}
Conte page
I have set the binding to one field here and that works, buit having to do that for the whole page is not what i want.
MasterPostsViewModel ViewModel;
protected override void OnAppearing()
{
base.OnAppearing();
BindingContext = ViewModel = new MasterPostsViewModel();
NameRequired.IsVisible = ViewModel.postViewModel.IsRequired;
}
Can you help please
instead of
IsVisible="{Binding PostViewModel.IsRequired, Source={x:Reference PostViewModel}}"
just use
IsVisible="{Binding postViewModel.IsRequired}"
your property name is postViewModel is lower case
also, get rid of this line - it will break the binding you have setup in the XAML
NameRequired.IsVisible = ViewModel.postViewModel.IsRequired;
I have a picker control:
<Picker Title="Number of People"
ItemsSource="{Binding SomeList, Source={x:Static local:MyModelHandler.MyModel}}"
SelectedItem="{Binding SomeListSelectedIndex, Source={x:Static local:MyModelHandler.MyModel}}">
</Picker>
when trying to build i get "No property, bindable property, or event found for 'ItemsSource'" error.
Above that i have a label:
<Label Text ="{Binding SomeLabel, Source={x:Static local:MyModelHandler.MyModel}, Mode=OneWay}"></Label>
And that binding works perfectly
MyModelHandler is an static class that allowes only one Model
public static class MyModelHandler
{
private static MyModel myModel = new MyModel();
public static MyModel MyModel
{
get
{
return myModel;
}
}
}
And Model is simple:
public class MyModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private int selectedNumber = 1;
private string someLabel = "";
public IList<int> SomeList
{
get
{
return Enumerable.Range(1, 10).ToList();
}
}
public int SomeListSelectedIndex
{
get
{
return SomeList.IndexOf(this.selectedNumberOfPeople);
}
set
{
this.selectedNumber = SomeList[value];
}
}
public double SomeLabel
{
get
{
return this.someLabel;
}
set
{
this.someLabel= value;
}
}
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
...
}
Edit: Using Xamarin 4.3
You might check your Xamarin.Forms version.
The ItemsSource property was introduced in Xamarin.Forms 2.3.4.184-pre1, see release notes here:
https://developer.xamarin.com/releases/xamarin-forms/xamarin-forms-2.3/2.3.4-stable/#2.3.4.184-pre1.
If you are using an older Xamarin.Forms version you will get the Xamarin.Forms XAML error "No property, bindable property, or event found for 'ItemsSource'".
That is a very strange way to set up the binding context for a view. The fact you have to specify the source for each element adds a lot of extra boilerplate code.
Try setting the bindingcontext to the model in the the view constructor
BindingContext = new MyModel ();
Then the XAML becomes
<Picker Title="Number of People"
ItemsSource="{Binding SomeList}"
SelectedItem="{Binding SomeListSelectedIndex}">
</Picker>
Or use a proper MVVM framework and save yourself a lot of grief. I can recommend FreshMvvm.
https://github.com/rid00z/FreshMvvm
I am using the standard pivot template in my WP7 app.
I have the MainViewModel class defined with a few extra properties:
public class MainViewModel : INotifyPropertyChanged
{
...
private MyClass selectedKey_m;
public MyClass SelectedKey
{
get
{
...
}
set
{
if (value != this.selectedKey_m)
{
this.selectedKey_m = value;
NotifyPropertyChanged("SelectedKey");
}
}
}
}
The App class has a view model instance:
private static MainViewModel viewModel = null;
public static MainViewModel ViewModel
{
get
{
// Delay creation of the view model until necessary
if (viewModel == null)
viewModel = new MainViewModel();
return viewModel;
}
}
My MainPage.xaml.cs sets the DataContext:
DataContext = App.ViewModel;
From here, I can set up two way bindings on ListBoxes and I know it works because if I put a breakpoint on the SelecetdKey property in my viewmodel I can see the setter get called.
My problem is that I have my own user control, with a bindable property, bound to the SelectedKey property of the view model, but the property in my user control never gets set when the viewmodel gets updated and I can't figure out why.
Here is my user control:
public partial class MyUserControl : UserControl
{
public static readonly DependencyProperty SelectedKeyProperty = DependencyProperty.Register(
"SelectedKey", typeof(MyClass), typeof(MyUserControl), new PropertyMetadata(null));
public MyClass SelectedKey
{
get { return (MyClass)this.GetValue(SelectedKeyProperty); }
set { this.SetValue(SelectedKeyProperty, value); }
}
}
And here is the xaml in my main page:
<local:MyUserControl x:Name="myUC" SelectedKey="{Binding Path=SelectedKey}">
I would expect that the setter for the SelectedKey property of my user control to get called when the SelectedKey property of the view model gets changed, but it doesn't.
I've also tried setting the datacontext of my user control in the xaml:
DataContext="{Binding Path=App.ViewModel}"
The debugger does not step into the setter, don't know why.
Try adding a callback invoked on property value changes :
public static readonly DependencyProperty SelectedKeyProperty = DependencyProperty.Register(
"SelectedKey", typeof(MyClass), typeof(MyUserControl), new PropertyMetadata(MyPropertyChanged));
private static void MyPropertyChanged( object sender, DependencyPropertyChangedEventArgs args)
{
}
Solved. I had to add the static method as ptauzen suggested, but also remove the DataContext binding statement from my xaml :
DataContext="{Binding Path=App.ViewModel}"
Because the MainPage sets the datacontext in the constructor, so because my user control is a child of the main page, it inherits the data context. All I needed was to ensure the binding of my user controls properties were set up:
SelectedKey="{Binding SelectedKey}"
How to bind nullable bool to checkbox in MVC 2. I try with this code in view:
<%: Html.CheckBoxFor(model => model.Communication.Before)%>
But show me compilation error.
Thanks in advance.
I know about this issue. You can try to use this workaround:
Create new property called Before in yours ViewModel:
public class YoursViewModel
{
public Communication Communication { get; set; }
public bool Before
{
get
{
bool result;
if (this.Communication.Before.HasValue)
{
result = (bool)this.Communication.Before.Value;
}
else
{
result = false;
}
return result;
}
set
{
this.Communication.Before = value;
}
}
}
Also you have to be careful for Communication property this have to be instanced before use. For example when you initialize ViewModel in controller you also have to initialize this property.
ControllerAction()
{
YoursViewModel model = ViewModelFactory.CreateViewModel<YoursViewModel >("");
model.Communication = new Communication ();
return View(model);
}
Thanks
Ivan Baev
A checkbox can have two states: ckecked/uncheked, true/false, 1/0. So trying to bind a checkbox to a property that could potentially have three states doesn't really fit the picture. I would recommend you adapting your view model so that it uses a non nullable boolean property. If in your domain model you have a nullable boolean which you cannot change you could do this in the mapping layer between your domain model and view model.
One way to bind Checkbox in MVC View
With EF database first, boolean (bit) field in the database produces a nullable bool? Property in the generated class. For demo I have a table named Dude with the fields
Id uniqueidentifier
Name varchar(50)
IsAwesome bit
The following class is generated by EF:
namespace NullableEfDemo
{
using System;
public partial class Dude
{
public System.Guid Id { get; set; }
public string Name { get; set; }
public Nullable<bool> IsAwesome { get; set; }
}
}
To be able to bind IsAwesome to checkbox I simply extend the class Dude. This is to avoid editing the generated class, if I need to refresh it. So I added a code file DudePartial.cs to my project (the name is irrelevant). Don’t forget to declare or using the project namespace:
namespace NullableEfDemo
{
partial class Dude
{
public bool Awesome
{
get { return IsAwesome ?? false; }
set { IsAwesome = value; }
}
}
}
This declares a new property Awesome of type bool that can be bound to the checkbox in the Edit view
#Html.CheckBoxFor(model => model.Awesome, new { #class = "control-label" })
In the HttpPost I’m binding the models Awesome property instead of IsAwesome.
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Edit([Bind(Include = "Id,Name,Awesome")] Dude dude)
{…
I'm once again in WPF binding hell :) I have a public class (Treatment) as follows:
public class Treatment()
{
...
public Ticker SoakTimeActual;
...
}
Within Ticker is a Dependency Property:
public class Ticker : FrameworkElement
{
// Value as string
public static readonly DependencyProperty DisplayIntervalProperty = DependencyProperty.Register("DisplayInterval", typeof(string), typeof(Ticker), null);
public string DisplayInterval
{
get { return (string)GetValue(DisplayIntervalProperty); }
set { SetValue(DisplayIntervalProperty, value); }
}
...
}
In my app, a single Treatment object is created and is meant to be easily accessible in XAML (in app.xaml ):
<Application.Resources>
<ResourceDictionary>
<u:Treatment
x:Key="currentTreatment" />
</ResourceDictionary>
</Application.Resources>
Now, I need to bind to the DisplayInterval dependency property of SoakTimeActual to display this text in its current state. Here is my attempt, which doesn't work:
<TextBlock
Text="{Binding Source={StaticResource currentTreatment}, Path=SoakTimeActual.DisplayInterval}"/>
This, of course, compiles ok, but will not display anything. I'm assuming I've made a mistake with change notification or DataContext or both.
Any insight is appreciated!
WPF binding only operates on properties, not fields.
Therefore, you need change your SoakTimeActual field to a property, like this:
public class Treatment
{
...
public Ticker SoakTimeActual { get; set; }
...
}