Hello I have question about a wpf/xaml text box c# implementation.
I am trying to figure out how in my c# code to know what the UpdateSourceTrigger is being used.
I am a newbie, so I would very much appreciate if people are patient with me and helpful.
In my C# I need to know how the data in the Text box is trying to be accessed using UpdateSourceTrigger. I know the property changed when my OnPropertyChanged() is called. But I also need to know how if the user is trying to use LostFocus or PropertyChanged in the C# code. This is so I can do some special processing for either case.
xaml
<TextBox>
<TextBox.Text>
<Binding Source="{StaticResource myDataSource}" Path="Name"
UpdateSourceTrigger="PropertyChanged"/>
</TextBox.Text>
</TextBox>
c#
protected void OnPropertyChanged(string name)
{
// If UpdateSourceTrigger= PropetyChanged then process one way
// If UpdateSourceTrigger= LostFocus then process one way
}
Is there any other methods that get called when using LostFocus?
Thanks you
You will have to get a reference to your TextBlock and get the binding expression then you will have access to the Binding information
Example:(no error/null checking)
<TextBox x:Name="myTextblock">
<TextBox.Text>
<Binding Source="{StaticResource myDataSource}" Path="Name"
UpdateSourceTrigger="PropertyChanged"/>
</TextBox.Text>
</TextBox>
var textblock = this.FindName("myTextBlock") as TextBlock;
var trigger = textblock.GetBindingExpression(TextBlock.TextProperty).ParentBinding.UpdateSourceTrigger;
// returns "PropertyChanged"
another way of getting the binding object is:
Binding binding = BindingOperations.GetBinding(myTextBox, TextBox.TextProperty);
if (binding.UpdateSourceTrigger.ToString().Equals("LostFocus"))
{
}
else
{
}
Related
I have a TextBox displaying the time part of a DateTime:
<TextBox HorizontalAlignment="Left" Height="23" Margin="0,13,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120" Validation.Error="Validation_OnError">
<TextBox.Text>
<Binding Path="MyDate" StringFormat="HH:mm" NotifyOnValidationError="True" UpdateSourceTrigger="PropertyChanged">
<Binding.ValidationRules>
<c:TimeValidator></c:TimeValidator>
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
</TextBox>
Is it possible to do the validation on property change, and the conversion on lost focus?
I want to have the validation on property changed, but I want to have my data source updated on lost focus. Otherwise, the converter will kick in while the user is editing in the TextBox. This might be a problem if the values is 10:50 and the user deletes the last number, so that the value becomes 10:5. The converter will then convert this to 10:50. This is okay to do on lost focus, but not on property changed. But for the sake of the validator, i want to validate on property change so the user have the red border as long as the entered value is not valid.
Yes! I was just wrestling with this. AFAIK, there is no XAML combination for this--it must be done in the codebehind, and you need a direct reference to the element.
Element.GetBindingExpression(PropertyName).ValidateWithoutUpdate();
You'll probably want to check that GetBindingExpression doesn't return null; this will run any converters you have attached (presumably to supply the converted value to converters with ValidationStep set to ConvertedProposedValue), but will not update the source. And, of course, you'll have to call this in some event, perhaps TextChanged or somesuch. Here is the MSDN documentation for it: https://msdn.microsoft.com/en-us/library/system.windows.data.bindingexpressionbase.validatewithoutupdate(v=vs.110).aspx
Use this code:
BindingExpression expression =
txtStudentName.GetBindingExpression(TextBox.TextProperty);
expression.ValidateWithoutUpdate();
If you want to update it's source after check use this code:
BindingExpression expression =
txtStudentName.GetBindingExpression(TextBox.TextProperty);
expression.ValidateWithoutUpdate();
if (expression!=null && !expression.HasError)
expression.UpdateSource();
I am trying to multibind a formatted double value to a text box. I have a converter which takes in a double and a Formatter object and returns a formatted string to be displayed. The double is bound to a particular data source and the formatter is a property in the view model. The problem I'm having is that I'm unable to bind to the view model property. This is my code in xaml
<StackPanel Grid.Row="0" Grid.Column="1">
<TextBlock HorizontalAlignment="Left" Style="{StaticResource HintDataItemsStyle}">
<TextBlock.Text>
<MultiBinding Converter="{StaticResource FormatConverter}">
<Binding Path="OpenValue" />
<Binding Path="XLabelFormatterY1" />
</MultiBinding>
</TextBlock.Text>
</TextBlock>
This is the property in the view model
private ILabelFormatter _labelFormatterY1;
public ILabelFormatter XLabelFormatterY1
{
get { return _labelFormatterY1; }
set
{
_labelFormatterY1 = value;
OnPropertyChanged("XLabelFormatterY1");
}
}
So, in my converter I'm able to pick up the value for "OpenValue" ,but the runtime is unable to find XLabelFormatterY1. Most of the examples I have seen for multibinding bind to gui components. I'm trying to bind to the view model and would appreciate all help.
Old question but without answer. I beleive that you are looking for this solution. If this answer doesn't work for you, try to explicitly set NotifyOnSourceUpdated="True" in the binding. And also double check if you have set correct AncestorType as wookietomwookie says in his answer.
I have a dialog in my project that the user enters some values in and when he hits OK I add an item to my database. I am using Entity Framework, so my adding to database code is something like this:
TransactionItem _item = new TransactionItem();
_item.DoctorID = (int)cmbDoctor.SelectedValue;
_item.TransactionCategoryID = (int)_dlg.cmbCat.SelectedValue;
_item.TransactionMethodID = (int)_dlg.cmbMethod.SelectedValue;
_item.Amount = int.Parse(_dlg.txtAmount.Text);
_item.DocumentID = _dlg.txtDocNum.Text;
_item.Info = _dlg.txtInfo.Text;
_item.Date = _dlg.dteDate.SelectedDate.ToString();
_db.TransactionItems.Add(_item);
_db.SaveChanges();
But the problem is there is nothing to bind and enable validating. I have tried making an empty object in my window and bind text box to it, but it had its own problems and didn't work as expected. I just want to when users enter values or when he hits OK, check if all of fields are valid (for example one of problems was if the user didn't enter any value, it is still valid even though the stringnotnull validator is enabled, but the most important problem was that it automatically set the textbox's text to null and mark it as a null value).
And I have made my own validator and here is a example of how I implemented them on one of my textboxes:
<TextBox Name="txtAmount" HorizontalAlignment="Left" Height="23" Margin="83,169,0,0" VerticalAlignment="Top" Width="224" Tag="T">
<TextBox.Text>
<Binding Path="myitem" ElementName="myWindow" UpdateSourceTrigger="PropertyChanged">
<Binding.ValidationRules>
<Validators:StringNullValidationRule/>
<Validators:IsNumericValidationRule/>
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
</TextBox>
Why don't you create a property in your viewmodel for each value the user needs to enter, and bind to it? Then you could use these properties when adding an item. For example:
ViewModel:
public int Amount { get; set; }
...
public void AddItem()
{
TransactionItem _item = new TransactionItem();
// ...
_item.Amount = Amount;
}
XAML:
<TextBox Name="txtAmount" HorizontalAlignment="Left" Height="23" Margin="83,169,0,0" VerticalAlignment="Top" Width="224" Tag="T">
<TextBox.Text>
<Binding Path="DataContext.Amount" ElementName="myWindow">
<Binding.ValidationRules>
<Validators:StringNullValidationRule/>
<Validators:IsNumericValidationRule/>
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
</TextBox>
I also recommend having a look at the INotifyDataErrorInfo interface (or the IDataErrorInfo interface if you're using .NET 4.0 or lower) to implement validations.
Use the IDataErrorInfo interface. You can implement it in your ViewModel or your Model class depending on your design. An example of how you can do it is in WPF: Validation made easy with IDataErrorInfo.
And I recommend you read this great Josh Smith article: WPF Apps With The Model-View-ViewModel Design Pattern. There you can see a good example of validation.
I have a MultiBinding that looks like this:
<MultiBinding Converter="{StaticResource MyConverter}">
<Binding Path="Object1.Object2.MyObject" />
<Binding Path="Object1.Object2.MyCollection[1]" />
<Binding Path="MyBoolean" />
</MultiBinding>
I only want to evaluate this MultiBinding (and thus call MyConverter.Convert()) when MyObject changes. I'm aware that I could set the MultiBinding's UpdateSourceTrigger to Explicit, but considering that Object1 and Object2 are regularly reassigned, I'd have to wire up a lot of PropertyChanged events in the code behind. Is it possible to achieve this in XAML?
Any help would be much appreciated - thanks!
Try setting the DataContext of your hosting control to that of Object2. Then you can bind to MyObject directly. Does this help? Of course, this still means changes to MyCollection and MyBoolean will also trigger the MultiBinding re-evaluation.
It would also help if you provided the context in which you're using your MultiBinding (i.e. is this returning text for a TextBlock?
EDIT:
In response to your comment, perhaps there's a different way. I assume your 3 multi-bound properties have individual PropertyChanged events. If your application allows, perhaps you could move those events out of the MyCollection and MyBoolean properties and into the MyObject property. For example:
public object MyObject
{
get { ... }
set
{
...
OnPropertyChanged("MyObject");
OnPropertyChanged("MyCollection");
OnPropertyChanged("MyBoolean");
}
}
Now I know this is a bit of a hack but this would trigger the MultiBinding only on change of MyObject.
EDIT #2:
Another option would be adding a EventTrigger to the hosting control, for example:
<EventTrigger RoutedEvent="MyObject.TargetUpdated">
<Setter TargetName="yourCheckBox" Property="Value">
<Setter.Binding>
<MultiBinding Converter="{StaticResource MyConverter}">
<Binding Path="MyObject" />
<Binding Path="MyCollection" />
<Binding Path="MyBoolean" />
</MultiBinding>
</Setter.Binding>
</Setter>
</EventTrigger>
Only catch here would be to make sure Mode=TwoWay on your checkbox binding.
I referred to this link.
Is there a way to template Binding.Converter and Binding.ValidationRules within a style?
Eg: I have the following textbox:
<TextBox x:Name="DepartTime" Height="23" HorizontalContentAlignment="Left" HorizontalAlignment="Left"
Margin="3" Width="140"
Style="{DynamicResource TimeOfDayTextBox}">
<TextBox.Text>
<!-- Textbox notifies changes when Text is changed, and not focus. -->
<Binding Path="FlightDepartTime" StringFormat="{}{0:hh:mm tt}" >
<Binding.Converter>
<convert:TimeOfDayConverter />
</Binding.Converter>
<Binding.ValidationRules>
<!-- Validation rule set to run when binding target is updated. -->
<validate:ValidateTimeOfDay ValidatesOnTargetUpdated="True" />
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
</TextBox>
.. I can't figure out how to incorporate the Converter and the Validation rule into my TimeOfDayTextBox style.
Many Thanks.
Unfortunately, no. The style could only set the Text property itself to a Binding. It cannot set attributes of the binding. Also, since Binding is not a DependencyObject there is no way to style a binding.
One option you have to make your code more concise is to use a custom MarkupExtension that creates the binding you want:
public class TimeOfDayBinding
: MarkupExtension
{
public PropertyPath Path { get; set; }
public override object ProvideValue(IServiceProvider serviceProvider)
{
var binding = new Binding()
{
Path = Path,
Converter = new TimeOfDayConverter(),
};
binding.ValidationRules.Add(new ValidateTimeOfDay()
{
ValidatesOnTargetUpdated = true,
});
return binding.ProvideValue(serviceProvider);
}
}
Given your control names, you may also want to use a time picker control instead of a TextBox. Check out this question: What is currently the best, free time picker for WPF?
A style can contain only a common set of property which can be applied to multiple controls. In your case, the converter and the validation rule aren't applied to the textbox, but to the content of the binding, so they are specific for a single element and cannot be used in a style.