How to copy object at Design-Time?
在Review项目时发现有个Design-Time Feature,要求实现对任意Object实现拷贝,使得Run起来之后是两个独立对象,看了code,发现只能对IComponent、IClonable对象做拷贝,其他的就只能算Limitation了,于是自己研究了一下,结合MS的实践,设计了个新的实现。
由于传入对象可以是任意对象,不可能一一列举并特殊处理,所以乍一看,问题有些棘手,阅读了一些MS实践后找到了一个可以让更多类型的对象实现拷贝的方法,以下是思路:
由于传入对象可以是任意对象,不可能一一列举并特殊处理,所以乍一看,问题有些棘手,阅读了一些MS实践后找到了一个可以让更多类型的对象实现拷贝的方法,以下是思路:
- 如果传入对象是值类型,直接返回即可;这里可以通过Type.IsValueType来判断。
- 如果传入对象是IComponent,需要首先获取DesignHost,通过DesignHost创建IComponent的新实例,然后通过PropertyDescriptor对每个可以设置的属性做递归拷贝(由于代码量,这里没有列出对Component对象拷贝的代码)。
- 如果传入对象实现IClonable,采用Clone方式获得拷贝对象并返回。
- 获取传入对象的TypeConverter,尝试转换传入对象成InstanceDescriptor,如果传入对象允许转换成InstanceDescriptor,同时转换的InstanceDescriptor实例不为null,并且已经完成,调用InstanceDescriptor.Invoke获取拷贝对象。
- 如果3没有成功,如果传入对象允许转换成string并且允许从string转换成实例,尝试转换传入对象成string,在从string转换得出新对象。
- 如果4都失败了,检查传入对象的类型是否支持Serialize,通过Type.IsSerializable来判断;如果支持,首先Serialize传入对象到MemeryStream,然后通过Deserialize得到新对象并返回。
- 如果以上均失败,说明对象不支持Design-Time拷贝,直接返回。
1private static object CopyValue(object value)
2{
3 if (value != null)
4 {
5 Type theTypeOfValue = value.GetType();
6 if (theTypeOfValue.IsValueType) // If the value is ValueType, return value is just the copy.
7 {
8 return value;
9 }
10
11 object newValue = null;
12 if (value is IComponent)
13 // If the value is IComponent, use DesignHost to create a new Component instance, and copy
14 // all properties from value to new Component instance, here CopyComponent is the entrance.
15 {
16 newVlaue = CopyComponent(value as IComponent);
17 }
18 if (newValue == null && value is ICloneable) // If the value is Cloneable, call IClone.Clone to clone object.
19 {
20 newValue = (value as ICloneable).Clone();
21 }
22 if (newValue == null)
23 {
24 TypeConverter theConverterOfValueObject = TypeDescriptor.GetConverter(value);
25 // If the value have a TypeConverter, try use TypeConverter to convert the object
26 // to InstanceDescriptor, if convert successfully, the new value is just copied one.
27 if (theConverterOfValueObject.CanConvertTo(typeof(InstanceDescriptor)))
28 {
29 InstanceDescriptor id = (InstanceDescriptor)theConverterOfValueObject.ConvertTo(null,
30 System.Globalization.CultureInfo.InvariantCulture,
31 value,
32 typeof(InstanceDescriptor));
33 if ((id != null) && id.IsComplete)
34 {
35 newValue = id.Invoke();
36 }
37 }
38 // if above convert failed, try convert the object to string.
39 if (((newValue == null) && theConverterOfValueObject.CanConvertTo(typeof(string)))
40 && theConverterOfValueObject.CanConvertFrom(typeof(string)))
41 {
42 object convertedObject = theConverterOfValueObject.ConvertToInvariantString(value);
43 newValue = theConverterOfValueObject.ConvertFromInvariantString((string)convertedObject);
44 }
45 }
46 // Above copy failed, try use Serialize.
47 if ((newValue == null) && theTypeOfValue.IsSerializable)
48 {
49 System.Runtime.Serialization.Formatters.Binary.BinaryFormatter bf
50 = new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();
51 MemoryStream ms = new MemoryStream();
52 bf.Serialize(ms, value);
53 ms.Position = 0;
54 newValue = bf.Deserialize(ms);
55 }
56 if (newValue != null)
57 {
58 return newValue;
59 }
60 }
61 // Can not copy the object, return original object.
62 return value;
63}
2{
3 if (value != null)
4 {
5 Type theTypeOfValue = value.GetType();
6 if (theTypeOfValue.IsValueType) // If the value is ValueType, return value is just the copy.
7 {
8 return value;
9 }
10
11 object newValue = null;
12 if (value is IComponent)
13 // If the value is IComponent, use DesignHost to create a new Component instance, and copy
14 // all properties from value to new Component instance, here CopyComponent is the entrance.
15 {
16 newVlaue = CopyComponent(value as IComponent);
17 }
18 if (newValue == null && value is ICloneable) // If the value is Cloneable, call IClone.Clone to clone object.
19 {
20 newValue = (value as ICloneable).Clone();
21 }
22 if (newValue == null)
23 {
24 TypeConverter theConverterOfValueObject = TypeDescriptor.GetConverter(value);
25 // If the value have a TypeConverter, try use TypeConverter to convert the object
26 // to InstanceDescriptor, if convert successfully, the new value is just copied one.
27 if (theConverterOfValueObject.CanConvertTo(typeof(InstanceDescriptor)))
28 {
29 InstanceDescriptor id = (InstanceDescriptor)theConverterOfValueObject.ConvertTo(null,
30 System.Globalization.CultureInfo.InvariantCulture,
31 value,
32 typeof(InstanceDescriptor));
33 if ((id != null) && id.IsComplete)
34 {
35 newValue = id.Invoke();
36 }
37 }
38 // if above convert failed, try convert the object to string.
39 if (((newValue == null) && theConverterOfValueObject.CanConvertTo(typeof(string)))
40 && theConverterOfValueObject.CanConvertFrom(typeof(string)))
41 {
42 object convertedObject = theConverterOfValueObject.ConvertToInvariantString(value);
43 newValue = theConverterOfValueObject.ConvertFromInvariantString((string)convertedObject);
44 }
45 }
46 // Above copy failed, try use Serialize.
47 if ((newValue == null) && theTypeOfValue.IsSerializable)
48 {
49 System.Runtime.Serialization.Formatters.Binary.BinaryFormatter bf
50 = new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();
51 MemoryStream ms = new MemoryStream();
52 bf.Serialize(ms, value);
53 ms.Position = 0;
54 newValue = bf.Deserialize(ms);
55 }
56 if (newValue != null)
57 {
58 return newValue;
59 }
60 }
61 // Can not copy the object, return original object.
62 return value;
63}
To be the apostrophe which changed “Impossible” into “I’m possible”
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