[英]Filtering the object of a type with OfType in C#
I have a base class Base, and class A/B that inherits from it. 我有一个基类Base,以及继承它的A / B类。
public class Base
{
int x;
}
public class A : Base
{
int y;
}
public class B : Base
{
int z;
}
I tried to use OfType to filter the only object that I need as follows: 我尝试使用OfType来过滤我需要的唯一对象,如下所示:
public static void RunSnippet()
{
Base xbase; A a; B b;
IEnumerable<Base> list = new List<Base>() {xbase, a, b};
Base f = list.OfType<A>; // I need to get only the object A
Console.WriteLine(f);
}
When I compiled the code, I got this error: 当我编译代码时,我收到此错误:
error CS0428: Cannot convert method group 'OfType' to non-delegate type 'Base'. 错误CS0428:无法将方法组'OfType'转换为非委托类型'Base'。 Did you intend to invoke the method? 你打算调用这个方法吗?
What's wrong with the code? 代码有什么问题?
There are two problems: 有两个问题:
OfType
returns IEnumerable<T>
, not T
OfType
返回IEnumerable<T>
,而不是T
Perhaps you wanted: 也许你想要:
Base f = list.OfType<A>().FirstOrDefault();
? ?
Brackets ? 括号?
This is a function and not operator. 这是一个功能而不是操作员。
Base f = list.OfType<A>()
Check out the reference: 查看参考:
Enumerable.OfType(Of TResult) Method Enumerable.OfType(Of TResult)方法
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