本文介绍了将不同类型的通用对象添加到通用列表中的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
是否可以将不同类型的通用对象添加到列表中?如下。
Is it possible to add different type of generic objects to a list?. As below.
public class ValuePair<T> { public string Name { get; set;} public T Value { get; set; }并说我拥有所有这些对象...
and let say I have all these objects...
ValuePair<string> data1 = new ValuePair<string>(); ValuePair<double> data2 = new ValuePair<double>(); ValuePair<int> data3 = new ValuePair<int>();我想将这些对象保存在通用列表中,例如
I would like to hold these objects in a generic list.such as
List<ValuePair> list = new List<ValuePair>(); list.Add(data1); list.Add(data2); list.Add(data3);有可能吗?
推荐答案通常,您必须使用 List< object> 或创建非通用基类,例如
In general, you'd have to either use a List<object> or create a non-generic base class, e.g.
public abstract class ValuePair { public string Name { get; set;} public abstract object RawValue { get; } } public class ValuePair<T> : ValuePair { public T Value { get; set; } public object RawValue { get { return Value; } } }然后,您可以拥有 List< ValuePair> ; 。
现在,有一个 例外:C#4中的协变/反变量类型。例如,您可以编写:
Now, there is one exception to this: covariant/contravariant types in C# 4. For example, you can write:
var streamSequenceList = new List<IEnumerable<Stream>>(); IEnumerable<MemoryStream> memoryStreams = null; // For simplicity IEnumerable<NetworkStream> networkStreams = null; // For simplicity IEnumerable<Stream> streams = null; // For simplicity streamSequenceList.Add(memoryStreams); streamSequenceList.Add(networkStreams); streamSequenceList.Add(streams);这不适用于您的情况,因为:
This isn't applicable in your case because:
- 您正在使用泛型类,而不是接口
- 您无法将其更改为泛型协变量接口,因为您有 T 进入了API的和出
- 您将值类型用作类型参数,而这些值类型不适用于泛型变量(因此 IEnumerable< int> 不是 IEnumerable< object> )
- You're using a generic class, not an interface
- You couldn't change it into a generic covariant interface because you've got T going "in" and "out" of the API
- You're using value types as type arguments, and those don't work with generic variable (so an IEnumerable<int> isn't an IEnumerable<object>)
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将不同类型的通用对象添加到通用列表中
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