在网上正则表达式测试仪，但不是在.NET正则表达式的作品 [英] regex works in online regex tester but not in .NET

问题描述

以下演示工作得很好，在网上而不是当我尝试在C＃中运行它/ .NET

the following demo works just fine online but not when I attempt to run it in c#/.NET

 var regex = new RegularExpressionAttribute(@"@(?!.*?\.\.)[^@]+$");
 Assert.IsTrue(regex.IsValid("[e-mail]"));

这里是一个的链接后，将解释正则表达式和我所试图做的。

here is a link to post that will explain the regex and what I am trying to do

推荐答案

RegularExpressionAttribute 需要字符串的全场比赛。

The RegularExpressionAttribute requires a full match of the string.

在你的情况，你只匹配开始于 @ 字符，让你在你的字符串之间的某处开始。这是RegularExpressionAttribute足够刚不好。你可以把它加入一个隐含的 ^ 在开始你的表达（和隐 $ 结尾太，这样就可以把那个一样）。

In your case, you are only matching starting at the @ character, so you start somewhere in between of your string. This is just not good enough for the RegularExpressionAttribute. You can think of it adding an implicit ^ at the start to your expression (and an implicit $ at the end too, so you can drop that as well).

因此，要解决这个问题，你需要确保它有一些匹配的开始，例如：一个 * ：

So to fix this, you need to make sure that it has something to match at the start to, e.g. a .*?:

new RegularExpressionAttribute(@".*?@(?!.*?\.\.)[^@]+");

然后它的作品。你不需要任何其他的正则表达式标志。

And then it works. You don’t need any other regular expression flags.

不幸的是，这种行为 RegularExpressionAttribute 在文档中提到无门。您可以在参考源然而验证：

Unfortunately, this behavior of RegularExpressionAttribute is mentioned nowhere in the documentation. You can verify it in the reference source however:

// We are looking for an exact match, not just a search hit. This matches what
// the RegularExpressionValidator control does
return (m.Success && m.Index == 0 && m.Length == stringValue.Length);

所以它在技术上不是一个额外的 ^ 和 $ 但找到一个匹配后，开始和结束索引都需要匹配字符串的开始和结束指数（基本上是同样的事情）。

So it’s technically not an added ^ and $ but after finding a match, the start and end index are required to match the string’s start and end index (which is essentially the same thing).

如果你仔细想想，这种行为使得验证有很大的意义。毕竟，你要确保一个字符串匹配一定全指定的格式，而不是只检查一些子是有效的。

And if you think about it, this behavior makes a lot of sense for validation. After all, you want to make sure that a string matches a certain full-specified format, and not just check if some substring is valid.

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