blocks|key|153081|text|在C#中，如果你反序列化为一个Dictionary<string,+string>，它会获取最后一个键值对：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|153082|string+json+=+@"{""a"":+""x"",+""a"":+""y""}";
var+d+=+JsonConvert.DeserializeObject<Dictionary<string,+string>>(json);
//+{+"a"+:+"y"+}|code-block|syntax|javascript|153083|如果您尝试反序列化到|153084|class+Foo
{
++++[JsonProperty("a")]
++++public+string+Bar+{+get;+set;+}

++++[JsonProperty("a")]
++++public+string+Baz+{+get;+set;+}
}

var+f+=+JsonConvert.DeserializeObject<Foo>(json);|153085|您会得到一个Newtonsoft.Json.JsonSerializationException异常。|153086|entityMap^0|F|Q|0|0|0|0|6|16|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|R|$]]

In C# if you deserialise to a <code>Dictionary&lt;string, string&gt;</code> it takes the last key value pair:

<pre><code>string json = @"{""a"": ""x"", ""a"": ""y""}";
var d = JsonConvert.DeserializeObject&lt;Dictionary&lt;string, string&gt;&gt;(json);
// { "a" : "y" }
</code></pre>

if you try to deserialise to 

<pre><code>class Foo
{
 [JsonProperty("a")]
 public string Bar { get; set; }

 [JsonProperty("a")]
 public string Baz { get; set; }
}

var f = JsonConvert.DeserializeObject&lt;Foo&gt;(json);
</code></pre>

you get a <code>Newtonsoft.Json.JsonSerializationException</code> exception.

blocks|key|153145|text|在处理同时接受XML和JSON的API时，我遇到了类似的问题，但没有说明它将如何处理所接受的JSON中的重复键。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|153146|以下是示例JSON的有效XML表示：|153147|<object>
++<a>x</a>
++<a>y</a>
</object>|code-block|syntax|javascript|153148|将其转换为JSON后，您将获得以下内容：|153149|{
++"object":+{
++++"a":+[
++++++"x",
++++++"y"
++++]
++}
}|153150|从一种处理重复键的语言到另一种语言的自然映射，在这里可以作为潜在的最佳实践参考。|153151|希望这对某些人有帮助！|153152|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

I came across a similar question when dealing with an API that accepts both XML and JSON, but doesn't document how it would handle what you'd expect to be duplicate keys in the JSON accepted.

The following is a valid XML representation of your sample JSON:

<pre><code>&lt;object&gt;
 &lt;a&gt;x&lt;/a&gt;
 &lt;a&gt;y&lt;/a&gt;
&lt;/object&gt;
</code></pre>

When this is converted into JSON, you get the following:

<pre><code>{
 "object": {
 "a": [
 "x",
 "y"
 ]
 }
}
</code></pre>

A natural mapping from a language that handles what you might call duplicate keys to another, can serve as a potential best practice reference here. 

Hope that helps someone!

blocks|key|153178|text|应该是唯一的并不意味着必须是唯一的。然而，如上所述，一些解析器会失败，而其他解析器只会使用解析的最后一个值。但是，如果规范被清理了一点，以允许重复，那么我可以看到一个使用事件处理程序将JSON转换为HTML或其他格式的用途……在这种情况下，解析JSON并创建另一种文档格式是完全有效的……|type|unstyled|depth|inlineStyleRanges|entityRanges|data|153179|[
++"div":
++{
++++"p":+"hello",
++++"p":+"universe"
++},
++"div":
++{
++++"h1":+"Heading+1",
++++"p":+"another+paragraph"
++}
]|code-block|syntax|javascript|153180|然后可以很容易地解析为html，例如：|153181|<body>
+<div>
++hello
++universe
+</div>
+<div>
++<h1>Heading+1</h1>
++another+paragraph
+</div>
</body>|153182|我看得出这个问题背后的原因，但事实是...我不会相信的。|153183|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

SHOULD be unique does not mean MUST be unique. However, as stated, some parsers would fail and others would just use the last value parsed. However, if the spec was cleaned up a little to allow for duplicates then I could see a use where you may have an event handler which is transforming the JSON to HTML or some other format... In such cases it would be perfectly valid to parse the JSON and create another document format...
<pre><code>[
 &quot;div&quot;:
 {
 &quot;p&quot;: &quot;hello&quot;,
 &quot;p&quot;: &quot;universe&quot;
 },
 &quot;div&quot;:
 {
 &quot;h1&quot;: &quot;Heading 1&quot;,
 &quot;p&quot;: &quot;another paragraph&quot;
 }
]
</code></pre>
could then easily parse to html for example:
<pre><code>&lt;body&gt;
 &lt;div&gt;
 &lt;p&gt;hello&lt;/p&gt;
 &lt;p&gt;universe&lt;/p&gt;
 &lt;/div&gt;
 &lt;div&gt;
 &lt;h1&gt;Heading 1&lt;/h1&gt;
 &lt;p&gt;another paragraph&lt;/p&gt;
 &lt;/div&gt;
&lt;/body&gt;
</code></pre>
I can see the reasoning behind the question but as it stands... I wouldn't trust it.

blocks|key|4659631|text|根据互联网工程任务组(IETF)发布的JSON当前标准RFC-7159，声明“对象中的名称应该是唯一的”。然而，根据定义IETF文档中使用的术语的RFC-2119，“应该”一词实际上意味着“……在特定情况下可能存在合理的理由来忽略特定的项目，但在选择不同的路线之前，必须理解并仔细权衡其全部含义。”这本质上意味着，虽然推荐使用唯一键，但这不是必须的。我们可以在JSON对象中有重复的键，但它仍然有效。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4659632|在实际应用中，我看到当在JSON中发现重复的键时，会考虑最后一个键的值。|4659633|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

According to RFC-7159, the current standard for JSON published by the Internet Engineering Task Force (IETF), states "The names within an object SHOULD be unique". However, according to RFC-2119 which defines the terminology used in IETF documents, the word "should" in fact means "... there may exist valid reasons in particular circumstances to ignore a particular item, but the full implications must be understood and carefully weighed before choosing a different course." What this essentially means is that while having unique keys is recommended, it is not a must. We can have duplicate keys in a JSON object, and it would still be valid.

From practical application, I have seen the value from the last key is considered when duplicate keys are found in a JSON.

Is this valid json?
<pre class="lang-json prettyprint-override"><code>{
 &quot;a&quot; : &quot;x&quot;,
 &quot;a&quot; : &quot;y&quot;
}
</code></pre>
<a href="http://jsonlint.com/" rel="nofollow noreferrer">http://jsonlint.com/</a> says yes.
<a href="http://www.json.org/" rel="nofollow noreferrer">http://www.json.org/</a> doesn't say anything about it being forbidden.
But obviously it doesn't make much sense, does it?
Most implementations probably use a hashtable so it is being overriden anyways.

Does JSON syntax allow duplicate keys in an object?

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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这是有效的json吗？{    "a" : "x",    "a" : "y"}同意了。没有说这是被禁止的。但很明显，这没有多大意义，不是吗？大多数实现可能使用哈希表，所以无论如何它都会被覆盖。

问JSON语法允许对象中有重复的键吗？
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