实例化任何类型(包括可为空结构)的变量的通用方法? [英] Generic method to instantiate a variable of any type (including nullable struct)?

问题描述

假设我有这个函数，它实例化一个 new 变量，具有默认/空值，适用于任何类型

Let's say I have this function which instantiates a new variable with default/empty value for any type

public static T GetDefault<T>() where T : new() //body of this method is the question
{
    T t = new T();
    return t;
}

上述函数的问题是当我有类似 int? 的 T 时.因为如果我有

The problem with the above function is when I have something like int? for T. Because if I have

int? t = new int?();

t 将为空！我不希望这种情况发生，而是希望返回 int 的默认值，即 0.

t will be null! I do not want this to happen, instead I want the default value of int to be returned which is 0.

为了解决这个问题，我可以为 int?、bool? 等使用不同的 GetDefault 函数重载，但这并不优雅.如果类型是 int? 或 bool? 等，我也可以在函数内部检查，但是我将如何实例化它的基本类型?

To solve this, I can have different overloads of GetDefault function for int?, bool? etc but that's not elegant. I can also check internally in the function if type is int? or bool? etc, but how would I go about instantiating it's base type?

或者问题归结为如何识别 T 是否为可空结构，以及如何实例化可空结构..

Or the question boils down to how to identify if T is nullable struct and accordingly how to instantiate the nullable struct..

推荐答案

Type realType = Nullable.GetUnderlyingType(typeof(T));
t = (T)Activator.CreateInstance(realType ?? typeof(T));

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