wg_cpso/DynamicDescriptors/DynamicPropertyDescriptor.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;

namespace DynamicDescriptors;

/// <summary>
/// A runtime-customizable implementation of <see cref="PropertyDescriptor"/>.
/// </summary>
public sealed class DynamicPropertyDescriptor : PropertyDescriptor
{
    /// <summary>
    /// The <see cref="PropertyDescriptor"/> on which this <see cref="DynamicPropertyDescriptor"/> is based.
    /// </summary>
    private readonly PropertyDescriptor _descriptor;

    /// <summary>
    /// A dictionary mapping editor base types to editor instances.
    /// </summary>
    private readonly IDictionary<Type, object> _editorDictionary;

    /// <summary>
    /// Gets or sets a value indicating whether the dynamic property descriptor is active.
    /// If not, it won't be returned by the <see cref="DynamicTypeDescriptor.GetProperties()"/> 
    /// or <see cref="DynamicTypeDescriptor.GetProperties(Attribute[])"/> methods.
    /// </summary>
    private bool _active;

    /// <summary>
    /// If this value is not null, it will be returned by the Category property;
    /// otherwise, the base descriptor's Category property will be returned.
    /// </summary>
    private string _categoryOverride;

    /// <summary>
    /// If this value is not null, it will be returned by the Converter property;
    /// otherwise, the base descriptor's Converter property will be returned.
    /// </summary>
    private TypeConverter _converterOverride;

    /// <summary>
    /// If this value is not null, it will be returned by the Description property;
    /// otherwise, the base descriptor's Description property will be returned.
    /// </summary>
    private string _descriptionOverride;

    /// <summary>
    /// If this value is not null, it will be returned by the DisplayName property;
    /// otherwise, the base descriptor's DisplayName property will be returned.
    /// </summary>
    private string _displayNameOverride;

    /// <summary>
    /// If this value is not null, it will be returned by the IsReadOnly property;
    /// otherwise, the base descriptor's IsReadOnly property will be returned.
    /// </summary>
    private bool? _isReadOnlyOverride;

    /// <summary>
    /// The order in which this property will be retrieved from its type descriptor.
    /// </summary>
    private int? _propertyOrder;

    /// <summary>
    /// Initializes a new instance of the <see cref="DynamicPropertyDescriptor"/> class.
    /// </summary>
    /// <param name="descriptor">
    /// The <see cref="PropertyDescriptor"/> on which this <see cref="DynamicPropertyDescriptor"/> will be based.
    /// </param>
    public DynamicPropertyDescriptor(PropertyDescriptor descriptor)
        : base(Preconditions.CheckNotNull(descriptor, nameof(descriptor)))
    {
        _descriptor = descriptor;
        _editorDictionary = new Dictionary<Type, object>();
        _active = true;
    }

    /// <summary>
    /// Gets or sets a value indicating whether the dynamic property descriptor is active.
    /// If not, it won't be returned by the <see cref="DynamicTypeDescriptor.GetProperties()"/>
    /// or <see cref="DynamicTypeDescriptor.GetProperties(Attribute[])"/> methods.
    /// </summary>
    public bool Active
    {
        get => _active;
        set => _active = value;
    }

    /// <summary>
    /// Returns a value indicating whether resetting an object changes its value.
    /// </summary>
    /// <param name="component">The component to test for reset capability.</param>
    /// <returns>true if resetting the component changes its value; otherwise, false.</returns>
    public override bool CanResetValue(object component)
    {
        return _descriptor.CanResetValue(component);
    }

    /// <summary>
    /// Gets the name of the category to which the member belongs,
    /// as specified in the <see cref="CategoryAttribute"/>.
    /// </summary>
    public override string Category => _categoryOverride ?? _descriptor.Category;

    /// <summary>
    /// Gets the type of the component this property is bound to.
    /// </summary>
    public override Type ComponentType => _descriptor.ComponentType;

    /// <summary>
    /// Gets the type converter for this property.
    /// </summary>
    public override TypeConverter Converter => _converterOverride ?? _descriptor.Converter;

    /// <summary>
    /// Gets the description of the member,
    /// as specified in the <see cref="DescriptionAttribute"/>. 
    /// </summary>
    public override string Description => _descriptionOverride ?? _descriptor.Description;

    /// <summary>
    /// Gets the name that can be displayed in a window, such as a Properties window.
    /// </summary>
    public override string DisplayName => _displayNameOverride ?? _descriptor.DisplayName;

    /// <summary>
    /// Gets an editor of the specified type.
    /// </summary>
    /// <param name="editorBaseType">
    /// The base type of editor, which is used to differentiate between multiple
    /// editors that a property supports.
    /// </param>
    /// <returns>
    /// An instance of the requested editor type, or null if an editor cannot be found.
    /// </returns>
    public override object GetEditor(Type editorBaseType)
    {
        if (editorBaseType != null)
        {
            if (_editorDictionary.TryGetValue(editorBaseType, out var editor))
            {
                return editor;
            }
        }

        return _descriptor.GetEditor(editorBaseType);
    }

    /// <summary>
    /// Returns the current value of the property on a component.
    /// </summary>
    /// <param name="component">
    /// The component with the property for which to retrieve the value.
    /// </param>
    /// <returns>The value of a property for a given component.</returns>
    public override object GetValue(object component)
    {
        return _descriptor.GetValue(component);
    }

    /// <summary>
    /// Gets a value indicating whether this property is read-only.
    /// </summary>
    public override bool IsReadOnly => _isReadOnlyOverride ?? _descriptor.IsReadOnly;

    /// <summary>
    /// Gets the order in which this property will be retrieved from its type descriptor.
    /// </summary>
    public int? PropertyOrder => _propertyOrder;

    /// <summary>
    /// Gets the type of the property.
    /// </summary>
    public override Type PropertyType => _descriptor.PropertyType;

    /// <summary>
    /// Resets the value for this property of the component to the default value.
    /// </summary>
    /// <param name="component">
    /// The component with the property value that is to be reset to the default value.
    /// </param>
    public override void ResetValue(object component)
    {
        _descriptor.ResetValue(component);
        OnValueChanged(component, EventArgs.Empty);
    }

    /// <summary>
    /// Sets the value of the component to a different value.
    /// </summary>
    /// <param name="component">
    /// The component with the property value that is to be set.
    /// </param>
    /// <param name="value">
    /// The new value.
    /// </param>
    public override void SetValue(object component, object value)
    {
        _descriptor.SetValue(component, value);
        OnValueChanged(component, EventArgs.Empty);
    }

    /// <summary>
    /// Determines a value indicating whether the value of this property needs to be persisted.
    /// </summary>
    /// <param name="component">
    /// The component with the property to be examined for persistence.
    /// </param>
    /// <returns>true if the property should be persisted; otherwise, false.</returns>
    public override bool ShouldSerializeValue(object component)
    {
        return _descriptor.ShouldSerializeValue(component);
    }

    #region Fluent interface

    /// <summary>
    /// Sets value that determines whether the dynamic property descriptor is active.
    /// </summary>
    /// <param name="active">
    /// The value that determines whether the dynamic property descriptor is active.
    /// </param>
    /// <returns>This <see cref="DynamicPropertyDescriptor"/> instance.</returns>
    public DynamicPropertyDescriptor SetActive(bool active)
    {
        _active = active;
        return this;
    }

    /// <summary>
    /// Sets the override for the <see cref="Category"/> property.
    /// </summary>
    /// <param name="category">The new value for the <see cref="Category"/> property.</param>
    /// <returns>This <see cref="DynamicPropertyDescriptor"/> instance.</returns>
    public DynamicPropertyDescriptor SetCategory(string category)
    {
        _categoryOverride = category;
        return this;
    }

    /// <summary>
    /// Sets the override for the <see cref="Converter"/> property.
    /// </summary>
    /// <param name="converter">The new value for the <see cref="Converter"/> property.</param>
    /// <returns>This <see cref="DynamicPropertyDescriptor"/> instance.</returns>
    public DynamicPropertyDescriptor SetConverter(TypeConverter converter)
    {
        _converterOverride = converter;
        return this;
    }

    /// <summary>
    /// Sets the override for the <see cref="Description"/> property.
    /// </summary>
    /// <param name="description">The new value for the <see cref="Description"/> property.</param>
    /// <returns>This <see cref="DynamicPropertyDescriptor"/> instance.</returns>
    public DynamicPropertyDescriptor SetDescription(string description)
    {
        _descriptionOverride = description;
        return this;
    }

    /// <summary>
    /// Sets the override for the <see cref="DisplayName"/> property.
    /// </summary>
    /// <param name="displayName">The new value for the <see cref="DisplayName"/> property.</param>
    /// <returns>This <see cref="DynamicPropertyDescriptor"/> instance.</returns>
    public DynamicPropertyDescriptor SetDisplayName(string displayName)
    {
        _displayNameOverride = displayName;
        return this;
    }

    /// <summary>
    /// Sets the editor for this type.
    /// </summary>
    /// <param name="editorBaseType">
    /// The base type of editor, which is used to differentiate between multiple editors
    /// that a property supports.
    /// </param>
    /// <param name="editor">
    /// An instance of the requested editor type.
    /// </param>
    /// <returns>This <see cref="DynamicPropertyDescriptor"/> instance.</returns>
    public DynamicPropertyDescriptor SetEditor(Type editorBaseType, object editor)
    {
        if (editorBaseType != null)
        {
            if (_editorDictionary.ContainsKey(editorBaseType))
            {
                if (editor == null)
                {
                    _editorDictionary.Remove(editorBaseType);
                }
                else
                {
                    _editorDictionary[editorBaseType] = editor;
                }
            }
            else
            {
                if (editor != null)
                {
                    _editorDictionary.Add(editorBaseType, editor);
                }
            }
        }

        return this;
    }

    /// <summary>
    /// Sets the order in which this property will be retrieved from its type descriptor.
    /// </summary>
    /// <param name="propertyOrder">The order in which this property will be retrieved.</param>
    /// <returns>This <see cref="DynamicPropertyDescriptor"/> instance.</returns>
    public DynamicPropertyDescriptor SetPropertyOrder(int? propertyOrder)
    {
        _propertyOrder = propertyOrder;
        return this;
    }

    /// <summary>
    /// Sets the override for the <see cref="IsReadOnly"/> property.
    /// </summary>
    /// <param name="readOnly">The new value for the <see cref="IsReadOnly"/> property.</param>
    /// <returns>This <see cref="DynamicPropertyDescriptor"/> instance.</returns>
    public DynamicPropertyDescriptor SetReadOnly(bool? readOnly)
    {
        _isReadOnlyOverride = readOnly;
        return this;
    }

    #endregion
}