blocks|key|130723|text|示例代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|130724|class+Example+{
++++private+string+warningHere;++++//+CS0649
++++void+UseField()+{
++++++++Console.WriteLine(warningHere);
++++}
}|code-block|syntax|javascript|130725|你必须让编译器相信你知道你在做什么，它拒绝考虑你使用反射将值插入字段的可能性。这很容易做到：|130726|++++private+string+warningHere+=+null;++//+Fine|130727|您可能会反对“但这完全没有意义！CLR已经将该字段初始化为null!”。这当然是真的。然而，消除这种多余的代码并没有什么坏处，这是jitter+optimizer的工作。它特别擅长删除不必要的空赋值。|offset|length|130728|130729|130730|+I可以在csproj中使用<NoWarn>0649</NoWarn>|blockquote|style|CODE|130731|130732|130733|一定要记住，这相当于用全局大锤解决局部问题。这个警告非常重要，你想让它对你编译的所有代码生效。为了演示一下，在上面的代码片段中，将class更改为struct，保持反射代码不变。请注意，您不能为warningHere字段赋值。在将结构传递给FieldInfo.SetValue()之前对其进行装箱的副作用，只有装箱的副本才会更新。如果没有警告来提醒您，这将是一个很难诊断的错误。|130734|在源代码中使用#pragma+warning是可以的，但并不优越，太容易忘记恢复它。|130735|该项目在两个月前才切换到使用MSBuild构建，请确保您的pull不是太老，并且您也切换了。你可以在github上提交一个bug，以提醒他们该功能是否仍然无效。如果你等不及了，一定要考虑挠挠它，自己来解决它。开源项目的最终好处:)|130736|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/4045073/17034^0|0|0|0|0|1T|G|0|0|0|0|E|L|0|0|0|1T|5|21|6|2P|B|0|7|F|0|0^^$0|@$1|2|3|4|5|6|7|1B|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|1C|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|1D|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|1E|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|1F|8|@]|9|@$M|1G|N|1H|1|1I]]|A|$]]|$1|O|3|-4|5|6|7|1J|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|1K|8|@]|9|@]|A|$]]|$1|Q|3|R|5|S|7|1L|8|@$M|1M|N|1N|T|U]]|9|@]|A|$]]|$1|V|3|-4|5|6|7|1O|8|@]|9|@]|A|$]]|$1|W|3|-4|5|6|7|1P|8|@]|9|@]|A|$]]|$1|X|3|Y|5|6|7|1Q|8|@$M|1R|N|1S|T|U]|$M|1T|N|1U|T|U]|$M|1V|N|1W|T|U]]|9|@]|A|$]]|$1|Z|3|10|5|6|7|1X|8|@$M|1Y|N|1Z|T|U]]|9|@]|A|$]]|$1|11|3|12|5|6|7|20|8|@]|9|@]|A|$]]|$1|13|3|-4|5|6|7|21|8|@]|9|@]|A|$]]]|14|$15|$5|16|17|18|A|$19|1A]]]]

Sample code:

<pre><code>class Example {
 private string warningHere; // CS0649
 void UseField() {
 Console.WriteLine(warningHere);
 }
}
</code></pre>

You have to convince the compiler that you know what you're doing, it refuses to consider the possibility that you use Reflection to poke a value into the field. That's pretty simple to do:

<pre><code> private string warningHere = null; // Fine
</code></pre>

You might object "But that's completely pointless! The CLR already initializes the field to null!". Which is certainly true. No harm done however, eliminating superfluous code like this is the job of the <a href="https://stackoverflow.com/a/4045073/17034">jitter optimizer</a>. It is particularly good at removing needless null assignments.

<hr>

<blockquote>
 I could have <code>&lt;NoWarn&gt;0649&lt;/NoWarn&gt;</code> in the csproj
</blockquote>

Do keep in mind that this is equivalent to solving a local problem with a global sledgehammer. This warning is pretty important, you want to have it in effect for all the code you compile. Just to demonstrate, in the above snippet change <code>class</code> to <code>struct</code>, keep the reflection code the same. And note that you cannot get give that <code>warningHere</code> field a value. A side-effect of the struct getting boxed before it is passed to FieldInfo.SetValue(), only the boxed copy is updated. That's a nasty bug to diagnose if you don't have a warning to alert you.

Using <code>#pragma warning</code> in the source is okayish, but not superior, too easy to forget to restore it.

The project switched to building with MSBuild just two months ago, do make sure your pull isn't too old and that you switched as well. You can file a bug at github to remind them if the feature is still awol. And do consider scratching that itch if you can't wait, fix it yourself. The ultimate benefit of an open source project :)

blocks|key|2908243|text|不能在xproj文件中指定编译器选项。按照以下步骤取消显示编译器警告：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2908244|2908245|打开项目的project.json文件。必须在此文件中指定所有编译器选项。|ordered-list-item|offset|length|style|CODE|2908246|将compilationOptions部分添加到文件的末尾：|2908247|2908248|"compilationOptions"：{+"noWarn"：649+}|2908249|保存文件并等待几秒钟，直到您在Visual+Studio.|unordered-list-item|2908250|
|2908251|Rebuild项目的状态栏中看到"Package+|2908252|2908253|+completed“消息。|2908254|2908255|这应该会抑制该警告。但是，有时(可能是一个bug)，即使在干净的构建之后，您对project.json所做的更改也不会生效。在这种情况下，通过对文件进行额外的虚拟更改和重建通常可以解决问题。|2908256|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/aspnet/Home/wiki/Project.json-file#compilation-options^0|0|0|5|C|0|1|I|0|0|0|0|0|0|0|0|0|0|13|C|0^^$0|@$1|2|3|4|5|6|7|19|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|1B|8|@$F|1C|G|1D|H|I]]|9|@]|A|$]]|$1|J|3|K|5|E|7|1E|8|@]|9|@$F|1F|G|1G|1|1H]]|A|$]]|$1|L|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|1J|8|@]|9|@]|A|$]]|$1|O|3|P|5|Q|7|1K|8|@]|9|@]|A|$]]|$1|R|3|S|5|6|7|1L|8|@]|9|@]|A|$]]|$1|T|3|U|5|Q|7|1M|8|@]|9|@]|A|$]]|$1|V|3|S|5|6|7|1N|8|@]|9|@]|A|$]]|$1|W|3|X|5|Q|7|1O|8|@]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|1P|8|@]|9|@]|A|$]]|$1|Z|3|10|5|6|7|1Q|8|@$F|1R|G|1S|H|I]]|9|@]|A|$]]|$1|11|3|-4|5|6|7|1T|8|@]|9|@]|A|$]]]|12|$13|$5|14|15|16|A|$17|18]]]]

Compiler options cannot be specified in the xproj file. Follow these steps to suppress a compiler warning:

<ol>
<li>Open the <code>project.json</code> file of the project. All compiler options must be specified in this file.</li>
<li>Add the <a href="https://github.com/aspnet/Home/wiki/Project.json-file#compilation-options" rel="nofollow">compilationOptions</a> section to the end of the file:

"compilationOptions": {
 "noWarn": [649]
}</li>
<li>Save the file and wait for few seconds until you see the "Package Restore completed" message in the status bar of Visual Studio.</li>
<li>Rebuild the project.</li>
</ol>

This should suppress the warning. However, sometimes (probably a bug), the changes you make to <code>project.json</code> do not take effect even after a clean build. In this case, by making additional dummy changes to the file and rebuilding usually solves the problem.

In my test project, I've got private fields that are not assigned to in the code, but are assigned with reflection.

When compiling I get warnings like:

<blockquote>
 Warning CS0649 Field 'CLASSNAME.FIELDNAME' is never assigned to, and will always have its default value null
</blockquote>

I've tried adding <code>&lt;NoWarn&gt;649&lt;/NoWarn&gt;</code> to the first PropertyGroup in the xproj. But I still get the errors.

Does NoWarn not work in DNX? Or am I doing something wrong? Is there any other solution to the problem?

NoWarn not working in DNX

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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在我的测试项目中，我有一些私有字段，这些字段在代码中没有被赋值，但通过反射被赋值。在编译时，我收到类似这样的警告： Warning CS0649字段'CLASSNAME.FIELDNAME‘从未被赋值，并且将始终具有其默认值null但我仍然会遇到错误。NoWarn在DNX中不工作吗？还是我做错了什么？这个问题有没有其他...

问NoWarn在DNX中不起作用
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