Question

I am working on wpf PropertyGrid(PG) control and I want the PG to support collection type(IList, ObservableCollection etc.) properties. I am bit confused on how to keep track of selected item(of that collection) and pass that to client.

Any ideas?

If the solution makes use of the Open Source WPF PropertyGrid (http://www.codeplex.com/wpg) I will implement the changes /additions back into the control.

Answer 1

No answers proves that there is no straight forward way of doing this. So I implemented this feature this way –

I created an attribute named RelatedItemSourcePropertyAttribute like this –

/// <summary>
/// Attribute to identify the related item source property.
/// Note: Property should be of IEnumerable type
/// </summary>
[global::System.AttributeUsage(AttributeTargets.Property, Inherited = true, AllowMultiple = false)]
public sealed class RelatedItemSourcePropertyAttribute : Attribute
{
    // See the attribute guidelines at 
    //  http://go.microsoft.com/fwlink/?LinkId=85236

    private string relatedPropertyName;
    public static readonly RelatedItemSourcePropertyAttribute Default = new RelatedItemSourcePropertyAttribute(string.Empty);

    /// <summary>
    /// Initializes a new instance of the <see cref="RelatedPropertyAttribute"/> class.
    /// </summary>
    /// <param name="relatedPropertyName">Name of the related property.</param>
    public RelatedItemSourcePropertyAttribute(string relatedPropertyName)
    {
        this.relatedPropertyName = relatedPropertyName;
    }

    /// <summary>
    /// Gets a value indicating whether [related property name].
    /// </summary>
    /// <value><c>true</c> if [related property name]; otherwise, <c>false</c>.</value>
    public string RelatedPropertyName
    {
        get { return relatedPropertyName; }
    }

    /// <summary>
    /// Determines whether the specified <see cref="System.Object"/> is equal to this instance.
    /// </summary>
    /// <param name="obj">The <see cref="System.Object"/> to compare with this instance.</param>
    /// <returns>
    ///     <c>true</c> if the specified <see cref="System.Object"/> is equal to this instance; otherwise, <c>false</c>.
    /// </returns>
    public override bool Equals(object obj)
    {
        if (!(obj is RelatedItemSourcePropertyAttribute))
            return false;
        if (obj == this)
            return true;
        return ((RelatedItemSourcePropertyAttribute)obj).relatedPropertyName == relatedPropertyName;
    }

    /// <summary>
    /// Returns a hash code for this instance.
    /// </summary>
    /// <returns>
    /// A hash code for this instance, suitable for use in hashing algorithms and data structures like a hash table. 
    /// </returns>
    public override int GetHashCode()
    {
        return relatedPropertyName.GetHashCode();
    }

    /// <summary>
    /// When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class.
    /// </summary>
    /// <returns>
    /// true if this instance is the default attribute for the class; otherwise, false.
    /// </returns>
    public override bool IsDefaultAttribute()
    {
        return relatedPropertyName == RelatedItemSourcePropertyAttribute.Default.relatedPropertyName;
    }
}

this attribute will take the property name of the related item source property(whose value will be used to fill the dropdown). It will be used like this –

    [RelatedItemSourceProperty("UnitNames")]
    public virtual string SelectedUnit
    {
        get { return (string)GetValue(SelectedUnitProperty); }
        set { SetValue(SelectedUnitProperty, value); }
    }
    public static readonly DependencyProperty SelectedUnitProperty =
        DependencyProperty.Register("SelectedUnit", typeof(string), typeof(BaseControl),
        new UIPropertyMetadata(string.Empty, new PropertyChangedCallback(SelectedUnitChangedCallBack)));


    public virtual ObservableCollection<string> UnitNames
    {
        get { return (ObservableCollection<string>)GetValue(UnitNamesProperty); }
        set { SetValue(UnitNamesProperty, value); }
    }
    public static readonly DependencyProperty UnitNamesProperty =
        DependencyProperty.Register("UnitNames", typeof(ObservableCollection<string>),
        typeof(BaseProperties), new PropertyMetadata(null)); //Validation

and then in property I binded the related item source property with the combobox.

Hope to see a better solution then this 🙂