c# - 如何为 wpf 设计器设置自定义控件的默认值？

Question

How do I set default values for my custom wpf components? I have a Textfield with the property "public Protection Protection{set;get;}". Protection is an enum:

public class Field3270Attributes{
    public enum Protection
    {
        PROTECTED,
        UNPROTECTED,
        AUTOSKIP
    }
}

The default value should be autoskip but protected is listed as the default value in the wpf designer since its the first element in the enum. Setting the protection in the Textfield constructor did not help. I've tried DependencyProperty which does work but I have to specify a callback(setProtection) if I want any values except the default value to work. If I dont specify a callback, changing values inside the wpf designer has no effect. Is there a way to get the same behavior without having to specify callback methods for every property?

public class Textfield{

    public static readonly DependencyProperty ProtectionProperty =
            DependencyProperty.Register("Protection",
                                        typeof(Field3270Attributes.Protection),
                                        typeof(Textfield3270),
                                        new FrameworkPropertyMetadata(Field3270Attributes.Protection.PROTECTED, setProtection));

    private static void setProtection(object sender, DependencyPropertyChangedEventArgs e)
    {
        Textfield field = (Textfield)sender;
        field.Protection = (Field3270Attributes.Protection)e.NewValue;
    }

    private Field3270Attributes.Protection protection;

    public Field3270Attributes.Protection Protection
    {
        get
        {
            return protection;
        }

        set
        {
            this.protection = value;

            if (value == Field3270Attributes.Protection.UNPROTECTED)
            {
                this.IsReadOnly = false;
                Background = Brushes.White;
            }
            else
            {
                this.IsReadOnly = true;
                Background = Brushes.LightSteelBlue;
            }
        }
    }

    public Textfield3270()
    {

        this.Protection = Field3270Attributes.Protection.PROTECTED;
    }

}

Answer 1

Your DependencyProperty definition defines the default value. Change the first parameter in the FrameworkPropertyMetadata from PROTECTED to AUTOSKIP

public static readonly DependencyProperty ProtectionProperty =
    DependencyProperty.Register("Protection",
        typeof(Field3270Attributes.Protection),
        typeof(Textfield3270),
        new FrameworkPropertyMetadata(Field3270Attributes.Protection.AUTOSKIP, setProtection));

EDIT

You are overwriting your Protection DependencyProperty by implementing your own version with the same name. Remove your definition of the Protection {get; set;} Protection {get; set;} completely.

If you want them to show up in the XAML designer, define the Get/Set as static methods like so:

public static Field3270Attributes.Protection GetProtection(DependencyObject obj)
{
    return (Field3270Attributes.Protection)obj.GetValue(ProtectionProperty);
}

public static void SetProtection(DependencyObject obj, Field3270Attributes.Protection value)
{
    obj.SetValue(ProtectionProperty, value);
}

If you want to attach some logic on PropertyChanged, you can use this code in your class constructor:

DependencyPropertyDescriptor dpd = DependencyPropertyDescriptor.FromProperty(Textfield.ProtectionProperty, typeof(Textfield));
if (dpd != null) dpd.AddValueChanged(this, delegate { Protection_Changed(); });

And your changed method would look like this:

private void Protection_Changed()
{
    Field3270Attributes.Protection protection = GetProtection(this);

    // Do something with value
}