扩展方法ConvertAll

本文介绍了扩展方法ConvertAll的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

正确使用ConverAll是什么?它将一种类型转换为另一种类型吗?

What is the proper use of ConverAll ? Will it convert one type to another type?

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List<int> intList = new List<int>(); intList.Add(10); intList.Add(20); intList.Add(30); intList.Add(33); var query= intList.ConvertAll(x=>(double)x);

为此，我可以使用cast或OfType<>.

for this i can use cast or OfType<>.

推荐答案

ConvertAll 不是扩展方法，它是List<T>本身的真实方法.

它返回一个包含转换后元素的新列表.因此，在您的示例中，query变量实际上不是查询，而是List<double>.

It returns a new list containing the converted elements. So in your example, the query variable isn't actually a query, it's a List<double>.

Cast 和 OfType are 扩展方法，它们在IEnumerable上运行并返回IEnumerable<T>.但是，它们不适合您指定的用途:Cast可以转换引用类型，但不能转换值类型，仅将其取消装箱. OfType不执行任何转换，它仅返回已具有指定类型的所有元素.

Cast and OfType are extension methods that operate on IEnumerable and return an IEnumerable<T>. However they're not suitable for your stated purpose: Cast can convert reference types but cannot convert value types, only unbox them. OfType doesn't perform any conversion, it just returns any elements that are already of the specified type.