首页 \ 问答 \ 更新属性或创建新元素（如果不存在）Lambda c＃(Update property or create new element if it does not exist Lambda c#)

更新属性或创建新元素（如果不存在）Lambda c＃(Update property or create new element if it does not exist Lambda c#)

 我有一个大的List <> of Name / Value对，需要能够找到此列表中是否存在特定的Name ...如果是，则更新该Value，如果不是，则创建一个新的Name / Value对并将其追加到我的列表。  
 Lambda语法是做什么的？  
 我试过使用.Where .DefaultIfEmpty，但它只是返回一个空对象但是没有将它附加到我原来的'myList'  
myList.Where(x => x.Name == 'some name').DefaultIfEmpty(new myobj(){ Name = 'some name').First().Value = 'some value';
 
 我必须这四个多个名称，所以如果我有一个简单的语法，将使它伟大=） 

I have a large List<> of Name/Value pairs and need to be able to find if a particular Name exist in this list...if so update that Value, if NOT then create a new Name/Value pair and append it to my List. 
What is the Lambda syntax to do this? 
I have tried using .Where .DefaultIfEmpty but it just returns an empty object but does not append it to my original 'myList' 
myList.Where(x => x.Name == 'some name').DefaultIfEmpty(new myobj(){ Name = 'some name').First().Value = 'some value';
 
I have to do this four multiple Names so if I had a simple syntax that would make it great =)

原文：https://stackoverflow.com/questions/17552180

更新时间：2022-04-23 17:04

最满意答案

 您可能已经解决了这个问题，因为它已经很老了，但这可能对其他人有所帮助。 问题可能是由于Visual Studio 2012中的项目属性中的错误。  
 如果你前往：  
 项目属性> C / C ++>预处理器>预处理器定义  
 并添加标志：  
 _NO_ASYNCRTIMP;  
 这可以防止编译器尝试从DLL中查找C ++ REST SDK函数。 它应该解决你的pplx链接错误。  
 其他一些重要的注意事项：  
 
  确保您正在为项目使用v110二进制文件 ，因为它们适用于Visual Studio 2012  
  您可能会在互联网上遇到一些不明智的建议，将“禁用wchar_t”作为本机类型。 这通常是一个坏主意，因为wchar_t是本机类型，而C ++ REST SDK依赖于它。  
  如果来自C ++ REST SDK的v110二进制文件未正确链接，请尝试Windows XP版本（v110_xp）  

You may have resolved this issue since it's so old, but this might help others. The issue could be due to an error in the project properties in Visual Studio 2012. 
If you head to: 
Project Properties > C/C++ > Preprocessor > Preprocessor Definitions 
And add the flag: 
_NO_ASYNCRTIMP; 
This prevents the compiler from trying to find the C++ REST SDK functions from a DLL. It should resolve your pplx linking errors. 
Some other points that are important to note: 
 
 ensure that you are using the v110 binaries for your project, as those are intended for Visual Studio 2012 
 You may run across some ill-advised suggestions around the internet to "disable wchar_t" as a native type. This is generally a bad idea, because wchar_t IS a native type and the C++ REST SDK depends on it. 
 If the v110 binaries from the C++ REST SDK aren't linking properly, try the Windows XP version (v110_xp)

更新属性或创建新元素（如果不存在）Lambda c＃(Update property or create new element if it does not exist Lambda c#)

最满意答案

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