如何在 C# .net 2.0 中使用反射访问索引器每个成员的属性

发布于 2024-08-08 07:10:29 字数 354 浏览 6 评论 0原文

我有以下方法：

object GetIndexer()

该方法的结果是类型的索引器：

SomeCollection<T>

现在 T 可以是任何东西，因为我知道每个 T 都扩展了类型 Y。

我尝试强制转换

SomeCollection<Y> result= (SomeCollection<Y>) GetIndexer()

它不起作用。

我需要知道的是如何使用反射访问索引器 SomeCollection 中每个项目的属性？

原文

I have the following method:

object GetIndexer()

The result of the method is an indexer of the type:

SomeCollection<T>

Now T can be anything, by I know that each T extends the type Y.

I tried casting

SomeCollection<Y> result= (SomeCollection<Y>) GetIndexer()

It didn't work.

What I need to know is how to access a property for each item in the indexer SomeCollection using Reflection?

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不知所踪 2024-08-15 07:10:29

对每个项目使用 GetType()，然后调用 GetProperties() 或 GetProperty(propertyName) 获取属性信息。这样，您就可以调用 GetValue() 传入您的对象。

一个例子：

    List<object> objects = new List<object>();
    // Fill the list
    foreach (object obj in objects)
    {
        Type t = obj.GetType();
        PropertyInfo property = t.GetProperty("Foo");
        property.SetValue(obj, "FooFoo", null);
        Console.WriteLine(property.GetValue(obj, null));            
    }

Use GetType() for each item, then call either GetProperties() or GetProperty(propertyName) to obtain the PropertyInfo. With this, you then call GetValue() passing in your object.

An example:

    List<object> objects = new List<object>();
    // Fill the list
    foreach (object obj in objects)
    {
        Type t = obj.GetType();
        PropertyInfo property = t.GetProperty("Foo");
        property.SetValue(obj, "FooFoo", null);
        Console.WriteLine(property.GetValue(obj, null));            
    }

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望她远 2024-08-15 07:10:29

一些上下文会有所帮助，但听起来你已经有了类似的东西，

class Foo<T> where T : Y {
    object GetIndexer() { /* ... */ }
}

在这种情况下，为什么不只是

    SomeCollection<Y> GetIndexer() { /* */ }

那样，不需要演员。

但我对您使用“索引器”一词感到有点困惑。 C# 的索引器是一种重载类型的 [] 运算符的方法，以便您可以执行以下操作：

MyCollectionType c = new MyCollectionType()
c["someValue"]

它们的定义如下：

class MyCollectionType {
    public string this [string index] // This particular indexer maps strings to strings, but we could use other types if we wished.
    get {} // Defines what to do when people do myCollection["foo"]
    set {} // Defines what to do when people do myCollection["foo"] = "bar"
}

SomeCollection 类型的对象不是一个索引器，它是一个集合。

Some context would be helpful, but it sounds like you've got something like

class Foo<T> where T : Y {
    object GetIndexer() { /* ... */ }
}

In that case, why not just

    SomeCollection<Y> GetIndexer() { /* */ }

That way, no cast is required.

But I am a little confused by your use of the term 'indexer'. An indexer for a C# is a way of overloading the [] operator for a type, so that you can do things like:

MyCollectionType c = new MyCollectionType()
c["someValue"]

They are defined like so:

class MyCollectionType {
    public string this [string index] // This particular indexer maps strings to strings, but we could use other types if we wished.
    get {} // Defines what to do when people do myCollection["foo"]
    set {} // Defines what to do when people do myCollection["foo"] = "bar"
}

An object of type SomeCollection<Y> isn't an indexer, it's a collection.

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浅暮の光 2024-08-15 07:10:29

SomeCollection 是否可枚举？如果是这样，您可以这样做

 var transformed = new SomeCollection<Y>();

 var someObjectCollection = (IEnumberable)GetIndexer();
 foreach (var someObjectin someObjectCollection);
     transformed.Add((Y)someObject);

或者等到 C# 4.0 为我们提供更多协变和逆变选项。

Is SomeCollection<T> enumerable? If so you could do

 var transformed = new SomeCollection<Y>();

 var someObjectCollection = (IEnumberable)GetIndexer();
 foreach (var someObjectin someObjectCollection);
     transformed.Add((Y)someObject);

Or wait until C# 4.0 gives us more covariance and contravariance options.

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