I need to update the binding source object with the control values only during a button click event.
But as my top level has datacontext being set, it's updating the source object whenever the control values change... Is it possible to set explicitly to update it during that event only keeping the datacontext as it is?
TextBox binding:
<TextBox x:Name="myTextBox" Text="{Binding MyTextProperty, UpdateSourceTrigger=Explicit}"/>
Button handler code:
myTextBox.GetBindingExpression(TextBox.TextProperty).UpdateSource();
Related
I previously had a ListView that was displaying an ObservableCollection of "Player" object properties, which I'm trying to convert into a DataGrid. I have most of it working, but currently having some issues with seeing changes on one particular property (Status), which is represented by a ComboBox. The idea is to allow players to override the "Status" value between a set of enums representing things like "Alive, Dead, Poisoned," etc. I've hooked up an EventHandler for when the ComboBox is closed and inside that handler, try to grab the sender object as a Player so I can send out the valid player values.
Here's a snippet of the XAML where I'm creating the ComboBox via a DataTemplate.
<DataGridTemplateColumn Header="Status">
<DataGridTemplateColumn.CellEditingTemplate>
<DataTemplate>
<ComboBox Name="cbStatus"
ItemsSource={Binding Source={StaticResource statusTypes}}"
SelecteItem="{Binding statusType, Mode=TwoWay}"
DropDownClosed="cbStatusType_DropDownClosed"/>
</DataTemplate>
</DataGridTemplateColumn.CellEditingTemplate>
</DataGridTemplateColumn>
Inside the Event Handler, I'm using the following to try and grab an "Player" object based on the values coming back from that particular row of the GUI.
Player playerOverridden = (Player)(sender as FrameworkElement).DataContext;
However, when I'm debugging the new playerOverridden when the ComboBox closes and a new value is selected, I'm not seeing that value being captured in playerOverridden.
This is pretty much the exactly what I was doing in a ListView with GridViewColumn.CellTemplates and it was working just fine. Not sure why the Status value is coming back as whatever it was initially set to instead of what the player has selected from the ComboBox.
Had to set the UpdateSourceTrigger on the SelectedItemBinding to be PropertyChanged, it works. Not sure why this has to be set explicitly inside a DataGrid where it's not something I needed to do in the ListView.
SelectedItem={"Binding statusType, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
I'm facing an odd issue with my WPF (MVVM) project.
I have a few controls which bind to the properties in the ViewModel. INotifyPropertyChanged is configured, everything (initially works). I type in some values into my controls and I click a button. I can see, by stepping through the code, all the property values are what they should be. So far, it is text book.
Now I notice the issue. After I click the button, some logic is performed, such as saving these values to a database. I can then edit the control values and then save to the database again. The properties at this point to do not update.
Binding clearly works, because the output shows no binding errors and when I click the Save button, the properties are correct. However, after I click the save button, and then change the property values, the properties are not updatdd. I cannot fathom why this is the case.
As a trial, I added the PropertyChanged to the update source trigger and this seems to fix the issue, however, I've never had to do this before. Any ideas what could be wrong?
I don't believe the answer is 2 way binding (I am happy to be wrong) because it binds!
<TextBox Text="{Binding DataSource, UpdateSourceTrigger=PropertyChanged}" Grid.Row ="1" Grid.Column="2" />
Where as normally I would use
<TextBox Text="{Binding DataSource}" Grid.Row ="1" Grid.Column="2" />
UpdateSourceTrigger property determines the time, when the binding has to be updated. The default value for this property is LostFocus. So by default, after you type something and move the focus out, the binding will update. If you set the property value to PropertyChanged, binding will update immediately once you entered the value in text box.
http://msdn.microsoft.com/en-us/library/system.windows.data.binding.updatesourcetrigger(v=vs.110).aspx
In your case, the binding is updated on button click, since focus transferred to Button from textbox. Once the UpdateSourceTrigger set to PropertyChanged, the binding will update on every text change.
<CheckBox x:Uid="cbRFEnableManualControl"
Grid.Column="0"
Grid.Row="0"
Name="cbRFEnableManualControl"
VerticalAlignment="Center"
Margin="0,0,0,12"
IsChecked="{Binding RFEnableManualControl, Mode=TwoWay}"
Checked="RFEnableManualControlChanged"
Unchecked="RFEnableManualControlChanged">
<CheckBox.Content x:Uid="EnableManualControlContent">
Enable manual control
</CheckBox.Content>
</CheckBox>
If I check this checkbox then i should enable some controls. I have a property "RFEnableManualControl" in my data model class, based on this value am enabling/disabling the other controls.
Issue is, i have another one button, if i check this checkbox after clicking this button the value is not set for this property. the execution is not going into this property and directly hitting the RFEnableManualControlChanged event.
In this another one button am calling the constructor of this data model class but am not assiging anything to this particular property.
I have an app and a Settings window with TabControl containing couple of TabItems. Each of them have some fields (textboxes) which are databinded to the same Singleton object.
Is there any elegant and WPF-like way to the the databinding only after Save button click?
Right now it's databinded immediately after changing the content of the textbox, and I want that singleton have old values and update them only after clicking the save button.
For your DataBinding object used in XAML for the Textbox, use the UpdateSourceTrigger property with value Explicit as below:
<TextBox Name="itemNameTextBox"
Text="{Binding Path=ItemName, UpdateSourceTrigger=Explicit}" />
When you set the UpdateSourceTrigger value to Explicit, the source value only changes when the application calls the UpdateSource method as below (you can put below code in Save Click event):
BindingExpression be = itemNameTextBox.GetBindingExpression(TextBox.TextProperty);
be.UpdateSource();
Instead of raising the notification of change on the set of each property (as that is what triggers the re-binding, and update), put all the raise notifications in the save button. Then when you click save, you save and tell the View to rebind to those (now set) properties.
To further this:
Bind to non singleton properties (as you want to keep the old settings until save is clicked) - without a raise notification on those properties.
In your save button, set your singleton properties, then raise all the notifications of the other properties.
In your cancel button, set your other properties to the values of the singleton properties, and raise all the notifications.
Don't forget to set your properties to the singleton properties when the view has been loaded the first time, and raise all the notifications (just like a cancel).
If you are using WPF change the UpdateSourceTrigger to LostFocus. I think that will solve the purpose.
Text="{Binding Path=MyText, UpdateSourceTrigger=LostFocus, Mode=TwoWay}"
I have a WPF MVVM app that contains a data entry form with several text boxes. I noticed that when the user is in a textbox and makes a change that the Context object does not know a change was made until the user tabs out of that text box. Once the user tabs out of the textbox, everything works fine. But I would like to know a change was made without the user having to tab off the textbox.
Is this possible?
The way my form works is that the Save and Cancel buttons bind to ICommands. These commands have a "CanSave" and "CanCancel" method that checks to see if the EntityState changed in anyway but allowing the buttons to enable. This works great but the user has to tab off the textbox to make things work.
How can I make this work without the user tabbing off a changed textbox?
Set the binding direction (Mode) of the TextBox to be TwoWay instead of the default and set the UpdateSourceTrigger to be PropertyChanged instead of default... like so:
<TextBox x:Name="txtPersonLastname" Text="{Binding Person.LastName, Mode=TwoWay, NotifyOnValidationError=True, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True, ValidatesOnExceptions=True}" />
(I have some additional attributes for validation in this excerpt.)
The key difference is the PropertyChanged which will update your backing property in the ViewModel. When the user types anything into the TextBox, that PropertyChanged event will fire, and in turn should trigger your CanSave, Save routines.
In Blend, it should look like this:
You have to chnage the Update Source Trigger Property to refelct the chages in your ViewModel
For Example
<TextBox Text={Binding Path=MyProperty,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}></TextBox>
Dont forget that My Property should fire Property Changed from ViweModel