英文:
Is it possible to type check using `is` without knowing the generic used?
问题
"是否可以检查一个变量是否属于使用泛型的特定类型，而不知道该泛型是什么？例如，下面的代码
using System;
using System.Collections.Generic;
public static class Program {
public static void Main(string[] args) {
List<string> list = new List<string>();
if (list is List<object>)
Console.WriteLine("Success");
else
Console.WriteLine("Failure");
}
}
输出"failure"，尽管"string"继承自"object"。如何使该程序识别出"list"是"List<T>"类型，而不知道"T"是什么？"
英文:
Is it possible to check if a variable is of a specific type that uses a generic, without knowing what that generic is? For example, the code
using System;
using System.Collections.Generic;
public static class Program {
public static void Main(string[] args) {
List<string> list = new List<string>();
if (list is List<object>)
Console.WriteLine("Success");
else
Console.WriteLine("Failure");
}
}
outputs failure even though string inherits from object. How can I make this program recognise that list is of type List<T> without knowing what T is?
答案1
得分: 2
你可以使用GetGenericTypeDefinition()方法来从List<T>中移除泛型T，得到List<>类型（注意没有T和空的<>），然后进行比较：
if (list.GetType().GetGenericTypeDefinition() == typeof(List<>))
Console.WriteLine("成功");
else
Console.WriteLine("失败");
英文:
You can do it with a help of GetGenericTypeDefinition() method to strip generic T from List<T> and have List<> type (note abscence of T and empty <>) to compare with:
if (list.GetType().GetGenericTypeDefinition() == typeof(List<>))
Console.WriteLine("Success");
else
Console.WriteLine("Failure");
答案2
得分: 2
你可以测试非泛型接口 IList：
if (list is IList)
Console.WriteLine("Success");
else
Console.WriteLine("Failure");
请注意，这也适用于数组。因此，使用模式匹配进行测试：
if (list is IList{ IsReadOnly: false }) ...
你可以同时将结果赋给一个新变量：
if (maybeList is IList{ IsReadOnly: false } list) ...
英文:
You can test for the non-generic interface IList:
if (list is IList)
Console.WriteLine("Success");
else
Console.WriteLine("Failure");
Note that this also succeds for arrays. Therefore test with (using pattern matching):
if (list is IList{ IsReadOnly: false }) ...
You can assign the result to a new variable at the same time:
if (maybeList is IList{ IsReadOnly: false } list) ...
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