使用.GetType（）或类似方法创建任意类型的对象...... [英] Using .GetType() or similar to create object of arbitrary type...

问题描述

......或者，或许更具沟通性，这样的事情：


输入someObjectsType = someObject.GetType（）;

someObjectsType newObject = new someObjectsType（）;


这可能吗？怎么样，怎么样？


非常感谢提前，

丹尼尔:)

解决方案

< da ******** @ gmail.com>写道：

...或者，或许，它可能更具沟通性，如下所示：

输入someObjectsType = someObject.GetType（）;
someObjectsType newObject = new someObjectsType（）;

您可以使用Activator.CreateInstance从其

类型创建对象。


Eq。

Paul E Collins写道：

< da ********@gmail.com>写道：

...或者，或许，它可能更具沟通性，如下所示：

输入someObjectsType = someObject.GetType（）;
someObjectsType newObject = new someObjectsType（）;

您可以使用Activator.CreateInstance从其
类型创建对象。

Eq。

嗨保罗:)


感谢您的回复。实际上，我认为在我的

问题中我有点过于通用了。真正发生的是......考虑这两个

（简化）类：


公共抽象类BaseClass

{

//一个尚未定义的项目集合，可以是类型

//" AppointmentCollection"，" TaskCollection"，或

//ContactCollection，取决于派生类

//被实例化（PimItemCollection是基本类型

//所有这些）：

protected PimItemCollection itemCollection;


public BaseClass（PimItemCollection itemCollection）

{

this.itemCollection = itemCollection; < br $>
}


}


公共类TasksClass：BaseClass

{

//这个派生类应该处理任务，

//所以它将一个ref传递给一个TaskCollection到

//基类。 br />
public TasksClass（）

：base（new OutlookSession（）。Tasks.Items）

{

}

}


好​​的，基类应该能做的一件事就是提供

a" backup" （xml序列化）

TaskCollection，ContactCollection或AppointmentCollection中的项目的功能（

包含PimItem类型的对象：Task，PimItem：Contact，PimItem：

分别预约），不知道前面的特定类型。

从itemCollection中取出PimItem对象的项目

罚款，我可以从此创建xml输出没有问题。但是当我需要恢复时，这是另一笔交易。也许是因为扩大演员阵容

与缩小演员阵容？


无论如何，我希望能够奏效的是以下内容。它应该是基类中的代码

：


//检测备份提供程序中项目的类型这是

itemCollection：

System.Type itemType = itemCollection [0] .GetType（）;


//读后备将数据转换为新数组：

XmlSerializer xmlSerializer = new

XmlSerializer（typeof（itemType []））;

StreamReader streamReader = new StreamReader （backupFile）;

XmlTextReader xmlTextReader = new

XmlTextReader（streamReader）;

itemType [] pimItems =

（itemType []）xmlSerializer.Deserialize（xmlTextReader）;

xmlTextReader.Close（）;

streamReader.Close（）;

文件。删除（backupFile）;


在这里，我收到很多错误，说类型或名称空间名称

'itemType''不能发现（你是否错过了使用指令或

汇编参考？）


所以，基本上，我是我真的不需要创建一个未知类型的新对象，但我需要能够使用它，就好像我在上面敲了一下

。 ..关于我怎么做这样的事情的想法？


再次感谢，

Daniel :)

你可以用反射做到这一点。


你知道反思吗？


问候，

Lars-Inge T？nnessen

....or, to put it perhaps more communicative, something like this:

Type someObjectsType = someObject.GetType();
someObjectsType newObject = new someObjectsType();

Is this possible? If so, how?

Thanks very much in advance,
Daniel :)

解决方案

<da********@gmail.com> wrote:

...or, to put it perhaps more communicative, something like this:

Type someObjectsType = someObject.GetType();
someObjectsType newObject = new someObjectsType();

You can use Activator.CreateInstance to create an object from its
type.

Eq.

Paul E Collins wrote:

<da********@gmail.com> wrote:

...or, to put it perhaps more communicative, something like this:

Type someObjectsType = someObject.GetType();
someObjectsType newObject = new someObjectsType();

You can use Activator.CreateInstance to create an object from its
type.

Eq.

Hi Paul :)

Thanks for your reply. Actually, I think I was a bit too generic in my
question. What''s really happening is this... Consider these two
(simplified) classes:

public abstract class BaseClass
{
// A yet undefined item collection that can be of type
// "AppointmentCollection", "TaskCollection", or
// "ContactCollection", depending on what derived class
// is instantiated (PimItemCollection is the base type
// for all these):
protected PimItemCollection itemCollection;

public BaseClass(PimItemCollection itemCollection)
{
this.itemCollection = itemCollection;
}

}

public class TasksClass : BaseClass
{
// This derived class is supposed to handle tasks,
// so it passes a ref to a TaskCollection to the
// base class.
public TasksClass()
: base(new OutlookSession().Tasks.Items)
{
}
}

Okay, so one thing that the base class should be able to do, is provide
a "backup" (xml serialization) functionality of the items in a
TaskCollection, ContactCollection, or AppointmentCollection (which
contain objects of type PimItem : Task, PimItem : Contact, PimItem :
Appointment, respectively), without knowing the specific type up front.
Pulling out items as PimItem objects from the itemCollection works
fine, and I can create xml output from this without problem. But when I
need to restore, it''s another deal. Perhaps because of widening casts
vs. narrowing casts?

Anyway, what I was hoping would work was the following. It''s code
that''s supposed to be in the base class:

// Detect the type of the items in the backup provider''s
itemCollection:
System.Type itemType = itemCollection[0].GetType();

// Read backed up data into a new array:
XmlSerializer xmlSerializer = new
XmlSerializer(typeof(itemType[]));
StreamReader streamReader = new StreamReader(backupFile);
XmlTextReader xmlTextReader = new
XmlTextReader(streamReader);
itemType[] pimItems =
(itemType[])xmlSerializer.Deserialize(xmlTextReader);
xmlTextReader.Close();
streamReader.Close();
File.Delete(backupFile);

Here, I get a lot of errors saying, "The type or namespace name
''itemType'' could not be found (are you missing a using directive or an
assembly reference?)"

So, basically, I don''t really need to create a new object of the
unknown type, but I need to be able to use it like I''m stabbing at
above... Any ideas of how I could do something like that?

Thanks again,
Daniel :)

You can do this with Reflection.

Do you know Reflection?

Regards,
Lars-Inge T?nnessen

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