API: 

TypeDescriptor.AddAttributes

TypeDescriptor.GetAttributes

注意：TypeDescriptor.AddAttributes添加的特性需要使用 TypeDescriptor.GetAttributes获取

根据api可以看到，该接口不仅可以给指定类（Type）添加特性，还能给其他任意object类型对象添加特性

添加：

public class DynamicCacheBufferAtrribute : Attribute
{
	public int Value;
    public DynamicCacheBufferAtrribute(int v)
    {
        Value = v;
    }
}
public class MyClass1
{
    
}
public class MyClass2
{
    public MyClass1 Class1Obj;
}

//需要添加的特性集
var attributes = new Attribute[]
{
	new DynamicCacheBufferAtrribute(123)
};


//给 MyClass1 类型添加、获取特性
TypeDescriptor.AddAttributes(typeof(MyClass1), attributes);
var attr = TypeDescriptor.GetAttributes(typeof(MyClass1))[typeof(DynamicCacheBufferAtrribute)] as DynamicCacheBufferAtrribute;
//var attr = TypeDescriptor.GetAttributes(field).OfType<DynamicCacheBufferAtrribute>().FirstOrDefault();


//给类对象添加、获取特性
var class1Inst = new MyClass1(); 
TypeDescriptor.AddAttributes(class1Inst , attributes);
var attr = TypeDescriptor.GetAttributes(class1Inst)[typeof(DynamicCacheBufferAtrribute)] as DynamicCacheBufferAtrribute;


//给FieldInfo添加、获取特性
var class2Inst = new MyClass2();
class2Inst.Class1Obj = new MyClass1(); 
var fieldInfo = class2Inst.GetType().GetField("Class1Obj");
TypeDescriptor.AddAttributes(fieldInfo, attributes);
var attr = TypeDescriptor.GetAttributes(fieldInfo)[typeof(DynamicCacheBufferAtrribute)] as DynamicCacheBufferAtrribute;



//给PropertyInfo添加、获取特性
var class2Inst = new MyClass2();
class2Inst.Class1Obj = new MyClass1(); 
var propertyInfo = class2Inst.GetType().GetProperty("Class1Obj");
TypeDescriptor.AddAttributes(propertyInfo, attributes);
var attr = TypeDescriptor.GetAttributes(propertyInfo)[typeof(DynamicCacheBufferAtrribute)] as DynamicCacheBufferAtrribute;


//其他object类型均可

删除：

//清空MyClaas1类型的所有DynamicCacheBufferAtrribute特性
var attrs = TypeDescriptor.GetAttributes(typeof(MyClass1)).OfType<DynamicCacheBufferAtrribute>().ToArray();
ArrayUtility.Clear(ref attrs);
TypeDescriptor.AddAttributes(typeof(MyClass1), attrs);