c# - 如何在属性网格中显示动态对象？

Question

我有一个自定义对象类型，它必须在 PropertyGrid 中可编辑:

public class CustomObjectType
{
    public string Name { get; set; }        
    public List<CustomProperty> Properties {get; set;}
}

其中有一个自定义属性列表:

public class CustomProperty
{
    public string Name { get; set; }
    public string Desc { get; set; }
    public Object DefaultValue { get; set; }    
    Type type;

    public Type Type
    {
        get
        {
            return type;
        }
        set
        {
                type = value;
                DefaultValue = Activator.CreateInstance(value);
        }              
    }
}

这里的主要问题是 PropertyGrid 控件不允许编辑，也不允许对属性 DefaultValue 使用适当的编辑工具，该属性预先通过设置 的值实例化code>CustomProperty 的字段 Type。

DefaultValue 的类型仅在运行时已知。

此外，我需要为 CustomProperty 的属性 Type 提供自定义 TypeConverter 以显示支持类型的下拉列表(对于例如，Int、String、Color、MyOwnClass)。

我该怎么做？

Answer 1

要走这条路，您需要为每个属性创建一个自定义 PropertyDescriptor。然后，您将通过自定义 TypeConverter 或(或者)ICustomTypeDescriptor/TypeDescriptionProvider 公开它。示例:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Windows.Forms;
[TypeConverter(typeof(CustomObjectType.CustomObjectConverter))]
public class CustomObjectType
{
    [Category("Standard")]
    public string Name { get; set; }
    private readonly List<CustomProperty> props = new List<CustomProperty>();
    [Browsable(false)]
    public List<CustomProperty> Properties { get { return props; } }

    private Dictionary<string, object> values = new Dictionary<string, object>();

    public object this[string name]
    {
        get { object val; values.TryGetValue(name, out val); return val; }
        set { values.Remove(name); }
    }

    private class CustomObjectConverter : ExpandableObjectConverter
    {
        public override PropertyDescriptorCollection GetProperties(ITypeDescriptorContext context, object value, Attribute[] attributes)
        {
            var stdProps = base.GetProperties(context, value, attributes);
            CustomObjectType obj = value as CustomObjectType;
            List<CustomProperty> customProps = obj == null ? null : obj.Properties;
            PropertyDescriptor[] props = new PropertyDescriptor[stdProps.Count + (customProps == null ? 0 : customProps.Count)];
            stdProps.CopyTo(props, 0);
            if (customProps != null)
            {
                int index = stdProps.Count;
                foreach (CustomProperty prop in customProps)
                {
                    props[index++] = new CustomPropertyDescriptor(prop);
                }
            }
            return new PropertyDescriptorCollection(props);
        }
    }
    private class CustomPropertyDescriptor : PropertyDescriptor
    {
        private readonly CustomProperty prop;
        public CustomPropertyDescriptor(CustomProperty prop) : base(prop.Name, null)
        {
            this.prop = prop;
        }
        public override string Category { get { return "Dynamic"; } }
        public override string Description { get { return prop.Desc; } }
        public override string Name { get { return prop.Name; } }
        public override bool ShouldSerializeValue(object component) { return ((CustomObjectType)component)[prop.Name] != null; }
        public override void ResetValue(object component) { ((CustomObjectType)component)[prop.Name] = null; }
        public override bool IsReadOnly { get { return false; } }
        public override Type PropertyType { get { return prop.Type; } }
        public override bool CanResetValue(object component) { return true; }
        public override Type ComponentType { get { return typeof(CustomObjectType); } }
        public override void SetValue(object component, object value) { ((CustomObjectType)component)[prop.Name] = value; }
        public override object GetValue(object component) { return ((CustomObjectType)component)[prop.Name] ?? prop.DefaultValue; }
    }
}


public class CustomProperty
{
    public string Name { get; set; }
    public string Desc { get; set; }
    public object DefaultValue { get; set; }
    Type type;

    public Type Type
    {
        get
        {
            return type;
        }
        set
        {
                type = value;
                DefaultValue = Activator.CreateInstance(value);
        }              
    }
}

static class Program
{
    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        var obj = new CustomObjectType
        {
            Name = "Foo",
            Properties =
            {
                new CustomProperty { Name = "Bar", Type = typeof(int), Desc = "I'm a bar"},
                new CustomProperty { Name = "When", Type = typeof(DateTime), Desc = "When it happened"},
            }
        };
        Application.Run(new Form { Controls = { new PropertyGrid { SelectedObject = obj, Dock = DockStyle.Fill } } });
    }
}