I'm trying to create a User Control with a property whose type is a class I've defined. I'm using a TypeConverter to allow the property to be processed as a string. The application correctly handles reading XAML where the property is a string, but if the property is set to a string through the property panel, then the XAML contains an expanded syntax breaking out the user-defined class.
Concretely, since that was a bit hard to follow, I'm following this Microsoft tutorial. I have the following code as a result:
Complex.cs
namespace WpfApplication1
{
[TypeConverter(typeof(ComplexTypeConverter))]
public class Complex
{
private double m_real;
private double m_imag;
public Complex() { }
public Complex(double r, double i)
{
m_real = r;
m_imag = i;
}
public double Real
{
get { return m_real; }
set { m_real = value; }
}
public double Imaginary
{
get { return m_imag; }
set { m_imag = value; }
}
public override string ToString()
{
return String.Format("{0},{1}", this.m_real, this.m_imag);
}
public static Complex Parse(string complexNumber)
{
if (String.IsNullOrEmpty(complexNumber))
{
return new Complex();
}
// The parts array holds the real and
// imaginary parts of the object.
string[] parts = complexNumber.Split(',');
return new Complex(double.Parse(parts[0].Trim()), double.Parse(parts[1].Trim()));
}
}
public class ComplexTypeConverter : TypeConverter
{
private static List<Complex> defaultValues = new List<Complex>();
static ComplexTypeConverter()
{
defaultValues.Add(new Complex(0, 0));
defaultValues.Add(new Complex(1, 1));
defaultValues.Add(new Complex(-1, 1));
defaultValues.Add(new Complex(-1, -1));
defaultValues.Add(new Complex(1, -1));
}
// Override CanConvertFrom to return true for String-to-Complex conversions.
public override bool CanConvertFrom(
ITypeDescriptorContext context,
Type sourceType)
{
if (sourceType == typeof(string))
{
return true;
}
return base.CanConvertFrom(context, sourceType);
}
// Override CanConvertTo to return true for Complex-to-String conversions.
public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
{
if (destinationType == typeof(string))
{
return true;
}
return base.CanConvertTo(context, destinationType);
}
// Override ConvertFrom to convert from a string to an instance of Complex.
public override object ConvertFrom(
ITypeDescriptorContext context,
System.Globalization.CultureInfo culture,
object value)
{
string text = value as string;
if (text != null)
return Complex.Parse(text);
return base.ConvertFrom(context, culture, value);
}
// Override ConvertTo to convert from an instance of Complex to string.
public override object ConvertTo(
ITypeDescriptorContext context,
System.Globalization.CultureInfo culture,
object value,
Type destinationType)
{
if (destinationType == null)
{
throw new ArgumentNullException("destinationType");
}
//Convert Complex to a string in a standard format.
Complex c = value as Complex;
if (c != null && this.CanConvertTo(context, destinationType))
{
return c.ToString();
}
return base.ConvertTo(context, culture, value, destinationType);
}
public override bool GetStandardValuesSupported(ITypeDescriptorContext context)
{
return true;
}
public override TypeConverter.StandardValuesCollection GetStandardValues(
ITypeDescriptorContext context)
{
StandardValuesCollection svc = new StandardValuesCollection(defaultValues);
return svc;
}
}
}
ComplexNumberControl.xaml.cs
namespace WpfApplication1
{
public partial class ComplexNumberControl : UserControl
{
public ComplexNumberControl()
{
InitializeComponent();
}
public Complex ComplexNumber
{
get
{
return (Complex)this.GetValue(ComplexNumberProperty);
}
set
{
this.SetValue(ComplexNumberProperty, value);
}
}
public static readonly DependencyProperty ComplexNumberProperty = DependencyProperty.Register(
"ComplexNumber",
typeof(Complex),
typeof(ComplexNumberControl),
new PropertyMetadata(new Complex()));
}
}
MainWindow.xaml
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525" xmlns:my="clr-namespace:WpfApplication1">
<Grid>
<my:ComplexNumberControl HorizontalAlignment="Left" Margin="88,78,0,0" x:Name="complexNumberControl1" VerticalAlignment="Top" />
</Grid>
</Window>
I can add ComplexNumber="0,0" to the ComplexNumberControl with no error (and I know, from more complicated assemblies, that the property is correctly handled as the Complex number 0 + 0i). However, if I edit ComplexNumber in the property panel, the XAML changes to:
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525" xmlns:my="clr-namespace:WpfApplication1">
<Grid>
<my:ComplexNumberControl HorizontalAlignment="Left" Margin="88,78,0,0" x:Name="complexNumberControl1" VerticalAlignment="Top">
<my:ComplexNumberControl.ComplexNumber>
<my:Complex Imaginary="-1" Real="1" />
</my:ComplexNumberControl.ComplexNumber>
</my:ComplexNumberControl>
</Grid>
</Window>
How can I ensure the generated XAML simply reads ComplexNumber="1,-1", instead of the verbose ComplexNumberControl.ComplexNumber construct?
You almost there and needs only two minor adjustments on Complex class to make it work as you expect:
1) Remove default public constructor:
public Complex() { } // <- delete this line
2) Add magical DesignerSerializationVisibility attribute to Real and Imaginary properties (or in general - to all properties with public setter):
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
public double Real
{
get { return m_real; }
set { m_real = value; }
}
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
public double Imaginary
{
get { return m_imag; }
set { m_imag = value; }
}
Hope this helps.