Walkthrough: Criar um conversor de tipos para o WPF Designer

  • Artigo

This walkthrough shows how to create a type converter for a custom type. The WPF Designer for Visual Studio uses the type converter to serialize your custom type to and from Extensible Application Markup Language (XAML).

In this walkthrough, you perform the following tasks:

  • Create the project.

  • Create the custom type.

  • Create the type converter.

  • Create a control which uses the custom type.

  • View the custom type in the Properties window.

When you are finished, you will be able to create type converters for your custom types.

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Pré-requisitos

You need the following components to complete this walkthrough:

  • Visual Studio 2010.

Creating the Project

The first step is to create the project for the application.

To create the project

Creating the Custom Type

In this procedure, you create a simple custom type named Complex, which represents a complex number. A complex number has a real part and an imaginary part, and these are exposed as double properties.

To create a custom type

  1. Add a new class named Complex.vb or Complex.cs to the TypeConverterExample project. For more information, see Como: Adicionar novos itens de projeto.

    The code file for the Complex class opens in the Code Editor.

  2. Replace the Complex class definition with the following code.

    <TypeConverter(GetType(ComplexTypeConverter))> _
Public Class Complex
    Private realValue As Double
    Private imaginaryValue As Double

    Public Sub New()

    End Sub

    Public Sub New(ByVal real As Double, ByVal imaginary As Double)
        Me.realValue = real
        Me.imaginaryValue = imaginary

    End Sub

    Public Property Real() As Double
        Get
            Return realValue
        End Get

        Set(ByVal value As Double)
            realValue = value
        End Set
    End Property

    Public Property Imaginary() As Double
        Get
            Return imaginaryValue
        End Get

        Set(ByVal value As Double)
            imaginaryValue = value
        End Set
    End Property

    Public Overrides Function ToString() As String
        Return String.Format( _
            CultureInfo.CurrentCulture, _
            "{0}{2}{1}", _
            Me.realValue, _
            Me.imaginaryValue, _
            CultureInfo.CurrentCulture.NumberFormat.NumberGroupSeparator)
    End Function

    Public Shared Function Parse(ByVal complexNumber As String) As Complex
        If String.IsNullOrEmpty(complexNumber) Then
            Return New Complex()
        End If

        'The parts array holds the real and imaginary parts of the object.
        Dim separator() As Char = {","}
        Dim parts() As String = complexNumber.Split(separator)

        If (parts.Length <> 2) Then
            Throw New FormatException( _
                String.Format( _
                    "Cannot parse '{0}' into a Complex object because " & _
                    "it is not in the '<real>, <imaginary>' format.", _
                complexNumber))
        End If

        Return New Complex( _
            Double.Parse(parts(0).Trim()), _
            Double.Parse(parts(1).Trim()))

    End Function

End Class

    [TypeConverter( typeof( ComplexTypeConverter ) )]
public class Complex
{
    private double realValue;
    private double imaginaryValue;

    public Complex()
    {
    }

    public Complex(double real, double imaginary)
    {
        this.realValue = real;
        this.imaginaryValue = imaginary;
    }

    public double Real
    {
        get
        {
            return realValue;
        }

        set
        {
            realValue = value;
        }
    }

    public double Imaginary
    {
        get 
        {
            return imaginaryValue; 
        }

        set 
        {
            imaginaryValue = value; 
        }
    }

    public override string ToString()
    {
        return String.Format(
            CultureInfo.CurrentCulture, 
            "{0}{2}{1}", 
            this.realValue, 
            this.imaginaryValue,
            CultureInfo.CurrentCulture.NumberFormat.NumberGroupSeparator);
    }

    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(',');       

        if (2 != parts.Length)
        {
            throw new FormatException(
                String.Format(
                "Cannot parse '{0}' into a Complex object because " +
                "it is not in the \"<real>, <imaginary>\" format.",
                complexNumber));
        }

        return new Complex(double.Parse(parts[0].Trim()), double.Parse(parts[1].Trim()));

    }
}

Creating the Type Converter

Now you define the type converter for the Complex class. The ComplexTypeConverter class converts a Complex object to its string representation and back. It also provides a list of default values, which can be displayed in a designer's Properties window.

To create the type converter

  1. After the Complex class definition, insert the following code for the ComplexTypeConverter class.

    Public Class ComplexTypeConverter
    Inherits TypeConverter

    Private Shared defaultValues As List(Of Complex) = New List(Of Complex)()

    Shared Sub New()
        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))
    End Sub

    ' Override CanConvertFrom to return true for String-to-Complex conversions.
    Public Overrides Function CanConvertFrom( _
        ByVal context As ITypeDescriptorContext, _
        ByVal sourceType As Type) As Boolean

        If sourceType Is GetType(String) Then
            Return True
        End If

        Return MyBase.CanConvertFrom(context, sourceType)

    End Function

    ' Override CanConvertTo to return true for Complex-to-String conversions.
    Public Overrides Function CanConvertTo( _
        ByVal context As System.ComponentModel.ITypeDescriptorContext, _
        ByVal destinationType As System.Type) As Boolean

        If destinationType Is GetType(String) Then
            Return True
        End If

        Return MyBase.CanConvertTo(context, destinationType)

    End Function

    ' Override ConvertFrom to convert from a string to an instance of Complex.
    Public Overrides Function ConvertFrom( _
        ByVal context As ITypeDescriptorContext, _
        ByVal culture As System.Globalization.CultureInfo, _
        ByVal value As Object) As Object

        If TypeOf value Is String Then
            Try
                Return Complex.Parse(CType(value, String))
            Catch ex As Exception
                Throw New Exception( _
                    String.Format( _
                        "Cannot convert '{0}' ({1}) because {2}", _
                        value, _
                        value.GetType(), _
                        ex.Message), ex)

            End Try
        End If

        Return MyBase.ConvertFrom(context, culture, value)

    End Function

    ' Override ConvertTo to convert from an instance of Complex to string.
    Public Overrides Function ConvertTo( _
        ByVal context As ITypeDescriptorContext, _
        ByVal culture As System.Globalization.CultureInfo, _
        ByVal value As Object, _
        ByVal destinationType As Type) As Object

        If destinationType Is Nothing Then
            Throw New ArgumentNullException("destinationType")
        End If

        Dim c As Complex = CType(value, Complex)

        If (c IsNot Nothing) Then
            If Me.CanConvertTo(context, destinationType) Then
                Return c.ToString()
            End If
        End If

        Return MyBase.ConvertTo(context, culture, value, destinationType)

    End Function


    Public Overrides Function GetStandardValuesSupported( _
        ByVal context As System.ComponentModel.ITypeDescriptorContext) As Boolean

        Return True

    End Function


    Public Overrides Function GetStandardValues( _
        ByVal context As System.ComponentModel.ITypeDescriptorContext) _
            As TypeConverter.StandardValuesCollection

        Dim svc As New StandardValuesCollection(defaultValues)
        Return svc

    End Function
End Class

    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)
        {
            try
            {
                return Complex.Parse(text);
            }
            catch (Exception e)
            {
                throw new Exception(
                    String.Format("Cannot convert '{0}' ({1}) because {2}", 
                                    value, 
                                    value.GetType(), 
                                    e.Message), e);
            }
        }

        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;
    }
}

  2. At the top of the file, import the System.ComponentModel namespace, which contains the TypeConverter implementation.

    Imports System.ComponentModel
Imports System.Globalization

    using System.ComponentModel;
using System.Globalization;

Creating a Control Which Uses the Custom Type

To see your custom type and its type converter in action on the design surface, you create a UserControl with a property of type Complex.

To create a control which uses the custom type

  1. Add a new WPF User Control named ComplexNumberControl.xaml to the TypeConverterExample project. For more information, see Como: Adicionar novos itens a um projeto WPF.

  2. View the code for ComplexNumberControl.

  3. Replace the ComplexNumberControl class definition with the following code.

    Partial Public Class ComplexNumberControl
    Inherits System.Windows.Controls.UserControl

    Private complexNumberValue As Complex

    Public Sub New()
        InitializeComponent()

    End Sub

    Public Property ComplexNumber() As Complex
        Get
            Return Me.GetValue(ComplexNumberProperty)
        End Get

        Set(ByVal value As Complex)
            Me.SetValue(ComplexNumberProperty, value)
        End Set
    End Property

    Public Shared ReadOnly ComplexNumberProperty As DependencyProperty = DependencyProperty.Register( _
      "ComplexNumber", _
      GetType(Complex), _
      GetType(ComplexNumberControl), _
      New PropertyMetadata(New Complex()))

End Class

    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()));
}

  4. Build the project.

Viewing the Custom Type in the Properties Window

You can view your custom type when the ComplexNumberControl is hosted in a WPF window.

To view the custom type in Properties window

  1. Abrir MainWindow. XAML na WPF Designer.

  2. In XAML view, replace the Window element with the following code.

    <Window x:Class="TypeConverterExample.MainWindow"
    xmlns="https://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:c="clr-namespace:TypeConverterExample"
    Title="Window1" Height="300" Width="300">
    <Grid>
        <c:ComplexNumberControl ComplexNumber="0,0" />
    </Grid>
</Window>

  3. Click in Design view. If necessary, click the Information bar at the top to reload the window.

  4. In the XAML view, click the ComplexNumberControl element.

  5. In the Properties window, click the ComplexNumber property.

    A drop-down arrow appears next to the ComplexNumber item.

  6. Click the drop-down to see the list of default values. Select the -1,-1 value.

    In the XAML view, the ComplexNumber assignment changes to "-1,-1".

Consulte também

Tarefas

Como: Implementar um conversor de tipo

Referência

TypeConverter

TypeConverterAttribute

XamlReader

XamlWriter

System.Windows.Markup

Outros recursos

XAML no WPF

Extensibilidade do WPF Designer