修改PropertyGrid中的结构属性

Question

为什么SomeClass.ClassField.StructField财产不会改变propertyGrid？看来,实例改变后propertyGrid不会调用.但是相同的代码可以很好地代替.SomeClass.ClassField.setSomeStructPointSomeStruct

[TypeConverter(typeof(ExpandableObjectConverter))]
public struct SomeStruct
{
    private int structField;

    public int StructField
    {
        get
        {
            return structField;
        }
        set
        {
            structField = value;
        }
    }

    public override string ToString()
    {
        return "StructField: " + StructField;
    }
}

[TypeConverter(typeof(ExpandableObjectConverter))]
public sealed class SomeClass
{
    public SomeStruct ClassField
    {
        get;
        set;
    }
}

...

var someClass = new SomeClass
{
    ClassField = new SomeStruct
    {
        StructField = 42
    }
};
propertyGrid.SelectedObject = someClass;

Answer 1

你需要一个特殊的TypeConverter来覆盖TypeConverter.GetCreateInstanceSupported,因为否则按照值/ copy-boxing魔法发生在场景后面的属性网格处理所有这些的方式.

这是适用于大多数值类型的一个.你声明它是这样的:

[TypeConverter(typeof(ValueTypeTypeConverter<SomeStruct>))]
public struct SomeStruct
{
    public int StructField { get; set; }
}


public class ValueTypeTypeConverter<T> : ExpandableObjectConverter where T : struct
{
    public override bool GetCreateInstanceSupported(ITypeDescriptorContext context)
    {
        return true;
    }

    public override object CreateInstance(ITypeDescriptorContext context, IDictionary propertyValues)
    {
        if (propertyValues == null)
            throw new ArgumentNullException("propertyValues");

        T ret = default(T);
        object boxed = ret;
        foreach (DictionaryEntry entry in propertyValues)
        {
            PropertyInfo pi = ret.GetType().GetProperty(entry.Key.ToString());
            if (pi != null && pi.CanWrite)
            {
                pi.SetValue(boxed, Convert.ChangeType(entry.Value, pi.PropertyType), null);
            }
        }
        return (T)boxed;
    }
}

请注意,它不支持纯字段结构,只支持具有属性的结构,但ExpandableObjectConverter也不支持这些结构,它需要更多代码才能执行此操作.