C# - 一个列表中的多个泛型类型
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C# - Multiple generic types in one list
提问by Carl
This is probably not possible, but I have this class:
这可能是不可能的，但我有这门课：
public class Metadata<DataType> where DataType : struct
{
private DataType mDataType;
}
There's more to it, but let's keep it simple. The generic type (DataType) is limited to value types by the where statement. What I want to do is have a list of these Metadata objects of varying types (DataType). Such as:
还有更多内容，但让我们保持简单。泛型类型 (DataType) 被 where 语句限制为值类型。我想要做的是列出这些不同类型（DataType）的元数据对象。如：
List<Metadata> metadataObjects;
metadataObjects.Add(new Metadata<int>());
metadataObjects.Add(new Metadata<bool>());
metadataObjects.Add(new Metadata<double>());
Is this even possible?
这甚至可能吗？
采纳答案by leppie
public abstract class Metadata
{
}
// extend abstract Metadata class
public class Metadata<DataType> : Metadata where DataType : struct
{
private DataType mDataType;
}
回答by bruno conde
Following leppie's answer, why not make MetaDataan interface:
按照 leppie 的回答，为什么不制作MetaData一个界面：
public interface IMetaData { }
public class Metadata<DataType> : IMetaData where DataType : struct
{
private DataType mDataType;
}
回答by Bryan Watts
I have also used a non-generic version, using the newkeyword:
我还使用了非通用版本，使用new关键字：
public interface IMetadata
{
Type DataType { get; }
object Data { get; }
}
public interface IMetadata<TData> : IMetadata
{
new TData Data { get; }
}
Explicit interface implementation is used to allow both Datamembers:
显式接口实现用于允许两个Data成员：
public class Metadata<TData> : IMetadata<TData>
{
public Metadata(TData data)
{
Data = data;
}
public Type DataType
{
get { return typeof(TData); }
}
object IMetadata.Data
{
get { return Data; }
}
public TData Data { get; private set; }
}
You could derive a version targeting value types:
您可以派生出一个针对值类型的版本：
public interface IValueTypeMetadata : IMetadata
{
}
public interface IValueTypeMetadata<TData> : IMetadata<TData>, IValueTypeMetadata where TData : struct
{
}
public class ValueTypeMetadata<TData> : Metadata<TData>, IValueTypeMetadata<TData> where TData : struct
{
public ValueTypeMetadata(TData data) : base(data)
{}
}
This can be extended to any kind of generic constraints.
这可以扩展到任何类型的通用约束。
