Question

我有以下代码：

public int Number(int x)
{
    return x > 0 ? x : throw new Exception();
}

目标很简单，操作员＆＃39;？＆＃39;我想检查一些值，如果它满足条件返回该值，如果不是 - 抛出一些错误。但VS Intellisense说：无效的表达式throw;我被迫使用其他运营商吗？

P.S。我想它与return throw new Exception();相同但仍然要确定。

Answer 1

改为写下：

public int Number(int x)
{
    if(x <= 0) throw new Exception();
    return x;
}

条件运算符需要返回一个公共基类型，但int和Exception没有。特别是投掷与返回相同的东西，即使你的方法返回 Exception（这很奇怪）这是不可能的。

来自MSDN：

first_expression和second_expression的类型必须相同，或者从一种类型到另一种类型必须存在隐式转换。

Answer 2

您可以在C＃7中执行此操作。您的方法可以进一步缩小为：

public int Number(int x) => x > 0 ? x : throw new Exception();

Answer 3

在C＃7.0之前，如果你想从表达式主体中抛出异常，你必须：

{
  "status": "ok",
  "count": 2,
  "count_total": 2,
  "pages": 1,
  "posts": [
    {
      "id": "9",
      "type": "post",
      "slug": "e5t-hal-3al2a",
      "url": "https:\/\/mahdii.000webhostapp.com\/?p=9",
      "status": "publish",
      "title": "e5t hal 3al2a",
      "title_plain": "e5t hal 3al2a",
      "date": "2017-02-09 19:35:05",
      "modified": "2017-02-09 19:35:05",
      "excerpt": "",
      "parent": "0",
      "category": [
        {
          "term_id": 1,
          "name": "Uncategorized",
          "slug": "uncategorized",
          "term_group": 0,
          "term_taxonomy_id": 1,
          "taxonomy": "category",
          "description": "",
          "parent": 0,
          "count": 1,
          "filter": "raw",
          "cat_ID": 1,
          "category_count": 1,
          "category_description": "",
          "cat_name": "Uncategorized",
          "category_nicename": "uncategorized",
          "category_parent": 0
        }
      ],
      "tag": [

      ],
      "author": [
        {
          "id": "1",
          "slug": "mahdi",
          "name": "mahdi",
          "first_name": "",
          "last_name": "",
          "nickname": "mahdi",
          "url": "",
          "description": "",
          "gravatar": "http:\/\/www.gravatar.com\/avatar\/b2f7652b7fd5e51e1ac71f6d23998c4c?s=100&d=mm&r=g"
        }
      ],
      "comment_count": "0",
      "comment_status": "open"
    },
    {
      "id": "2",
      "type": "page",
      "slug": "sample-page",
      "url": "https:\/\/mahdii.000webhostapp.com\/?page_id=2",
      "status": "publish",
      "title": "Sample Page",
      "title_plain": "Sample Page",
      "date": "2017-02-09 12:31:52",
      "modified": "2017-02-09 12:31:52",
      "excerpt": "This is an example page. It's different from a blog post because it will stay in one place and will show up in your site navigation (in most themes). Most people start with &hellip; <a href=\"https:\/\/mahdii.000webhostapp.com\/?page_id=2\"> Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a>",
      "parent": "0",
      "category": [

      ],
      "tag": [

      ],
      "author": [
        {
          "id": "1",
          "slug": "mahdi",
          "name": "mahdi",
          "first_name": "",
          "last_name": "",
          "nickname": "mahdi",
          "url": "",
          "description": "",
          "gravatar": "http:\/\/www.gravatar.com\/avatar\/b2f7652b7fd5e51e1ac71f6d23998c4c?s=100&d=mm&r=g"
        }
      ],
      "comment_count": "0",
      "comment_status": "closed"
    }
  ]
}

在C＃7.0中，上面现在简化为：

return x > 0 ? x : new Func<int>(() => { throw new Exception(); })();

Answer 4

随着？表达式双方必须返回相同的类型，在您的情况下不是这样。用。。。来代替


if(x > 0) return x
throw new Exception();

C＃运营商？抛出异常

4 个答案: