c＃三元运算符返回不同类型 [英] c# Ternary operator returning different types

问题描述

我试图使用三元组返回不同类型，虽然我似乎遇到一些问题。我的问题是三元运算符不能返回不同类型？

  //这行会导致错误
 propertyGrid.Instance =（directoryRecord.directoryInfo！= null）
？ directoryRecord.directoryInfo 
：directoryRecord.fileInfo; 
 
 //编译精细
 propertyGrid.Instance = directoryRecord.directoryInfo; 
 
 //编译精细
 propertyGrid.Instance = directoryRecord.fileInfo; 
  

错误

无法确定条件表达式的类型，因为有
在'System.IO.DirectoryInfo'和
'System.IO.FileInfo'之间没有隐式转换

解决方案

不，这不会像这样工作。

em>具有特定类型。

您可以使其工作方式如下：

  propertyGrid.Instance =（directoryRecord.directoryInfo！= null）
？ （object）directoryRecord.directoryInfo 
：（object）directoryRecord.fileInfo; 
  

I'm trying to use the ternary to return differing types, although I seem to be encountering some problems. My question is can the ternary operator not return differing types?

// This line causes an error
propertyGrid.Instance = (directoryRecord.directoryInfo != null) 
    ? directoryRecord.directoryInfo 
    : directoryRecord.fileInfo;

// Compiles fine
propertyGrid.Instance = directoryRecord.directoryInfo;

// Compiles fine
propertyGrid.Instance = directoryRecord.fileInfo;

Error

Type of conditional expression cannot be determined because there is no implicit conversion between 'System.IO.DirectoryInfo' and 'System.IO.FileInfo'

解决方案

No, this doesn't work like that.
The expression of a conditional operator has a specific type. Both types used in the expression must be of the same type or implicitly convertible to each other.

You can make it work like this:

propertyGrid.Instance = (directoryRecord.directoryInfo != null) 
    ? (object)directoryRecord.directoryInfo 
    : (object)directoryRecord.fileInfo;

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