data binding update when value changes, not when tabbing out - c#

Is there a property or setting to force a bound control in Winforms to update the object it is bound to when the input value, either in a textbox or whatever, actually changes?
And not after the control is tabbed out of.

Assuming you have already bound the textbox to something:
Select the textbox in the designer
Click property "databindings"
Click property "advanced"
In this dialog look for the "datasource update mode"
Select onpropery changed instead of onvalidate
Now the datasource gets updated on every change of the text property of the textbox.

Related

System.Window.Forms.CheckBox databinding won't get hit

I have a problem with System.Window.Forms.CheckBox databinding. I generate a checkbox and then map it's value to a property on a BindingSource via
Checkbox → Properties → DataBindings → Checked → BindingSource - PropertyValue
I then have a CheckedChanged event that get's triggered when i click on the checkbox. However on click the BindingSource property is not updated. Because of this I have to use checkbox Design -> Name to get the value of the checkbox. Should the binding be done in another way? I can map strings this way with no problem but for some reason a checkbox bool seems harder to map.
When you setup data-binding, the default value for Data Source Update Mode is OnValidation which means Data source is updated when the control property is validated. So in the current state if you move the focus to another control the data-binding will update the data source property.
If you want data source update whenever the value of the control property changes, you should change the setting to OnPropertyChanged.
You can change the setting using designer this way:
Select the control and in property grid, expand (DataBindings) and click ... in from of (Advanced) to open Formatting and Advanced Binding.
In the window, from the left Property list, select the property which you want to perform advanced setting for it.
At right pane, from Data Source Update Mode select OnPropertyChanged. To learn more about other available values, take a look at DataSourceUpdateMode documentations.

Selected List view item not taking focus Win 10 UWP

I bound Selected Item of ListView with my viewmodel property SelectedLayout and I have changed SelectedLayout from code behind. The Selected Item is changing properly But focus is not coming to the selected item. It is clear when I press enter. Focus is at button where it was before setting SelectedLayout . How can I get Focus to the selected Item in windows 10 UWP?
Just changing the value of bound property does not automatically change the focus to the corresponding element. It is done by design, as in many cases you do not need to change focus, just to update the value of the control. So what you need to do is to implement the logic of changing focus in your MVVM code.
To do that, the good practice would be to use Attached Property as outlined here: Set focus on textbox in WPF from view model (C#). In this manner, you can bind the IsFocused attached property of your controls to your ViewModel, and then implement any focusing logic in the ViewModel.

C# WPF prevent binding back to listview

I have a Listview in my WPF windows and there I have a binding to a property List<User> users;
I also have a edit/add form beside the listview where I want to edit the user and click on the save button to save the user. I have the bindingContext of the groupbox of the form set to currentUser which is set on OnSelectionChange event of the ListView. Everything(bindings) work fine but my problem is:
When I change the text of the textbox which are bound to currentUser and leave the textbox, it is automatically updated in the listView. I first want to click on 'Save User' before the ListView is updated. How can I achieve this?
Thank you.
Option1:
You could set UpdateSourceTrigger of your textbox (on your update form) to Explicte,
and only call UpdateSource method, when clicking Save.
Option2:
You could also set Listview's each column's BindingMode to OneTime, and update/refresh it's DataContext after Save. (ie. by setting View's DataContext to null and then set it back.)

Why are changes not recognized when focus leaves control?

I have a class that implements INotifyPropertyChanged. I use a binding source to bind the class to a form's controls. I'm using WinForms.
When I enter some text in a textbox and click on the Save button (I don't leave the textbox), the property bound to the textbox doesn't get updated.
Is this normal behavior? And if yes, is there a way to accept all changes?

WPF RaisePropertyChanged event on lost focus

I have a C# WPF MVVM application that works fine.
The only problem is when I modify a textbox and click on the menu. If I do that without clicking on another control, the view->viewmodel event is never fired because the textbox hasn't lost focus. Correct me if I am wrong, but I think the RaisePropertyChanged is only fired on LostFocus (or OnBlur, or any similar event).
So, clicking on the menu save button right after editing the textbox causes the viewmodel to save the data using old values.
So, resuming:
This sequence works fine:
Edit the text box
Click on another control
RaisePropertyChanged is fired, the viewmodel is updated
Click on save button on the menu
Data Saved with correct values
This sequence gives me an error:
Edit the text box
Click on save button on the menu
Data Saved with correct values
How to solve this?
This is a common gotcha with TextBoxes in both WPF and WinForms. You can get around this by instructing the binding system to update the VM with every change to the TextBox instead of when it loses focus. To do this, set the UpdateSourceTrigger of the binding to PropertyChanged. This will write back to the VM any time the TextBox raises the PropertyChanged event for its Text property.
<TextBox Text="{Binding MyText, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
For the TextBox.Text dependency property, its default UpdateSourceTrigger is LostFocus (ie, your view model property gets updated when the control loses focus). To make the property update immediately whenever text is entered, set UpdateSourceTrigger=PropertyChanged. (See the link above for more info -- it actually covers your example specifically.)

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