Image source value - a combination of hardcoded strings and binding - wpf

I have an image in my xaml:
<Image Grid.Column="0" Grid.Row="0" Grid.RowSpan="2" Width="30" Height="30"></Image>
The source for the image is like this:
..\Images\MyFolder\1.png
..\Images\MyFolder\2.png
..\Images\MyFolder\3.png
Basically, the name of the .png file is the id of the items.
In my ViewModel I have a field which represents the id, its name is myId.
How do I add this kind of source - with two hardcoded values and one binding value?

Bind the Image source with the id and apply a converter to create the image path.
The xaml will be:
ente<Image Source="{Binding Path=myId, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay, Converter={StaticResource ConvImageSource}}"/>
And add the resouce at the top:
<Window.Resources>
<local:ImageSourceConverter x:Key="ConvImageSource"/>
</Window.Resources>
And the converter can be:
public class ImageSourceConverter : IValueConverter
{
#region IValueConverter Members
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
String myId = System.Convert.ToString(value);
String imagePath = SPECIFY_IMAGE_PATH;
String imageExtn = SPECIFY_IMAGE_Extn;
// Create the image source
String imageSource = String.Concat(imagePath, myId, imageExtn);
return imageSource;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return value;
}
#endregion
}
Hope this will help.

Related

Dynamically switching between canvases wpf

I have multiple canvas images of different types (image source, geometry, path) and wish to only show 1 depending on a string binding.
whats the best way to do this?
i'd like it to be reusable so i can place this code inside a user control and then have many of these images around the app and i select which 1 is shown.
Like so:
<CanvasImage Image="Pie"/>
<CanvasImage Image="Dog"/>
Would it be too computationally expensive to have them all declared in the user control view and use visibility bindings
Pie canvas example:
<canvas>
<Data ="m24,98,07">
</canvas>
Dog canvas example:
<canvas>
<image source="">
<canvas>
This converter return an image source directly, depending on the value it receives.
namespace TestTreeView.Views
{
public class StringToImageConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
string file = "";
string v = value as string;
switch (v)
{
case "Pie":
file = #".\path\to\your\pie.jpg";
break;
case "Dog":
file = #".\path\to\your\dog.jpg";
break;
default:
return null;
}
return new BitmapImage(new Uri(file, UriKind.RelativeOrAbsolute));
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
}
Usage in XAML:
<Window xmlns:local="clr-namespace:YourNamespace.Views" ...>
<Window.Resources>
<local:StringToImageConverter x:Key="stringToImageConverter"/>
</Window.Resources>
<Grid>
<Canvas>
<Image Source="{Binding YourString, Converter={StaticResource stringToImageConverter}}"/>
</Canvas>
</Grid>
</Window>
Original answer
I think you need to use a Converter.
It will take a ConverterParameter, a String, that will tell what the binded value is expected to be, and return a Visiblity to indicate if the canvas should be visible or not.
namespace YourNamespace.Views
{
public class StringToCanvasVisibilityConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
string v = value as string;
string p = parameter as string;
return (v != null && p != null && v == p) ? Visibility.Visible : Visibility.Collapsed;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
}
Usage in XAML:
<Window xmlns:local="clr-namespace:YourNamespace.Views" ...>
<Window.Resources>
<local:StringToVisibilityConverter x:Key="stringToVisibilityConverter"/>
</Window.Resources>
<Grid>
<Canvas Visibility="{Binding YourString, Converter={StaticResource stringToVisibilityConverter}, ConverterParameter=Pie}"/>
<Canvas Visibility="{Binding YourString, Converter={StaticResource stringToVisibilityConverter}, ConverterParameter=Dog}"/>
</Grid>
</Window>

How to bind size properties with a unit different than px?

The default unit for the size of every user control is px, but it is possible to easily set the size to a different unit, for instance:
<Canvas Height="29.7cm" Width="21cm" />
But what should I do if I want to bind these properties? How do I retain the information about my desired unit?
You can create a custom converter which converts the string representation to double (using LengthConverter):
[ValueConversion(typeof(string), typeof(double))]
public class SizeConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
double size = (double)new LengthConverter().ConvertFrom(value.ToString());
return size;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotSupportedException("SizeConverter is a oneway converter.")
}
}
After that you can refer that converter from your XAML:
<src:SizeConverter x:Key="sizeConverter"/>
<Canvas Height="{Binding Path=Height, Converter={StaticResource sizeConverter}}"
Width="{Binding Path=Width, Converter={StaticResource sizeConverter}}" />
(Here Height and Width are strings available in the DataContext of your Canvas.)

WPF - binding complex objects to simple controls

I have created a class named "BoundProperty" which contains a property "Value".
Binding to a property which is an instance of that class looks this way
(Age is a BoundProperty):
<TextBox Text="{Binding MyModel.Age.Value, Mode=TwoWay}" />
Is there a way to make the binding look this way and additionally still retain it two-way?
<TextBox Text="{Binding MyModel.Age, Mode=TwoWay}" />
I can't use implicit/explicit conversion operators, for this "BoundProperty" initialization requires special parameters, which need to be copied from original object.
Thanks,
AD
If Value is public you can use ValueConverter:
public class BoundPropertyConverter:IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
var age = value as BoundProperty;
if (age == null)
return string.Empty;
return age.Value;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
int age;
if (int.TryParse(value.ToString(), out age))
return new BoundProperty() {Value = age};
return null;
}
}
Then in xaml define namespace to this converter
xmlns:converters="clr-namespace:Your.Namespace"
And then in Resources area write something like this:
<converters:BoundPropertyConverter x:Key="BoundPropertyConverter"/>
And last but not least:
<TextBox Text="{Binding MyModel.Age, Mode=TwoWay, Converter={StaticResource BoundPropertyConverter}" />

Binding-driven Indexed Property Doesn't Return

Public Class View
Public Property Items As String() = {"One", "Two", "Three"}
Public Property Index As Integer = 0
End Class
It's instance is set as DataContext of this XAML:
<Window>
<StackPanel>
<ListBox ItemsSource="{Binding Items}" SelectedIndex="{Binding Index}"/>
<Label Content="{Binding Items[Index]}"/>
</StackPanel>
</Window>
But this doesn't work.
<Label Content="{Binding Items[{Binding Index}]}"/>
This neither.
<Label Content="{Binding Items[0]}"/>
This works.
Is there any solution except making extra property in view? Something directly in XAML?
I'm afraid it's not possible without some code-behind, but using reflection and dynamic, you can create a converter that can do this (it would be possible without dynamic, but more complex):
public class IndexerConverter : IValueConverter
{
public string CollectionName { get; set; }
public string IndexName { get; set; }
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
Type type = value.GetType();
dynamic collection = type.GetProperty(CollectionName).GetValue(value, null);
dynamic index = type.GetProperty(IndexName).GetValue(value, null);
return collection[index];
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotSupportedException();
}
}
Put following into resources:
<local:IndexerConverter x:Key="indexerConverter" CollectionName="Items" IndexName="Index" />
and use it like this:
<Label Content="{Binding Converter={StaticResource indexerConverter}}"/>
EDIT: The previous solution doesn't update properly when the values change, this one does:
public class IndexerConverter : IMultiValueConverter
{
public object Convert(object[] value, Type targetType, object parameter, CultureInfo culture)
{
return ((dynamic)value[0])[(dynamic)value[1]];
}
public object[] ConvertBack(object value, Type[] targetType, object parameter, CultureInfo culture)
{
throw new NotSupportedException();
}
}
In resources:
<local:IndexerConverter x:Key="indexerConverter"/>
Usage:
<Label>
<MultiBinding Converter="{StaticResource indexerConverter}">
<Binding Path="Items"/>
<Binding Path="Index"/>
</MultiBinding>
</Label>
What you write in the binding markup extension is assigned to the Path property by default, this property is a string so any dynamic content you refer to inside it will not be evaluated. There is no simple XAML-only method to do what you try to do.
Why don't use this:
<StackPanel>
<ListBox Name="lsbItems" ItemsSource="{Binding Items}" SelectedIndex="{Binding Index}"/>
<Label Content="{Binding ElementName=lsbItems, Path=SelectedItem}"/>
</StackPanel>

Set value to null in WPF binding

please take a look at the following line
<TextBox Text="{Binding Price}"/>
This Price property from above is a Decimal? (Nullable decimal).
I want that if user deletes the content of the textbox (i.e. enters empty string, it should automatcally update source with null (Nothing in VB).
Any ideas on how I can do it 'Xamly'?
I am using .NET 3.5 SP1 so it's very simple:
<TextBox Text="{Binding Price, TargetNullValue=''}"/>
Which stands for (thanks Gregor for your comment):
<TextBox Text="{Binding Price, TargetNullValue={x:Static sys:String.Empty}}"/>
sys is the imported xml namespace for System in mscorlib:
xmlns:sys="clr-namespace:System;assembly=mscorlib"
Hope that helped.
This value converter should do the trick :
public class StringToNullableDecimalConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter,
CultureInfo culture)
{
decimal? d = (decimal?)value;
if (d.HasValue)
return d.Value.ToString(culture);
else
return String.Empty;
}
public object ConvertBack(object value, Type targetType,
object parameter, CultureInfo culture)
{
string s = (string)value;
if (String.IsNullOrEmpty(s))
return null;
else
return (decimal?)decimal.Parse(s, culture);
}
}
Declare an instance of this converter in the ressources :
<Window.Resources>
<local:StringToNullableDecimalConverter x:Key="nullDecimalConv"/>
</Window.Resources>
And use it in your binding :
<TextBox Text="{Binding Price, Converter={StaticResource nullDecimalConv}}"/>
Note that TargetNullValue is not appropriate here : it is used to define which value should be used when the source of the binding is null. Here Price is not the source, it's a property of the source...
You can try using a ValueConverter (IValueConverter)
http://msdn.microsoft.com/en-us/library/system.windows.data.ivalueconverter.aspx
Of the back of my head here, something like:
public class DoubleConverter : IValueConverter
{
public object Convert(object value, Type targetType,
object parameter, CultureInfo culture)
{
return (double)value;
}
public object ConvertBack(object value, Type targetType,
object parameter, CultureInfo culture)
{
var doubleValue = Convert.ToDouble(value);
return (doubleValue == 0 ? null : doubleValue);
}
}
(Might need some tweaking though)

Resources