blocks|key|4032986|text|您可以使用合同来实现这一点，但这是同一个概念。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4032987|无论如何，这应该是一个很好的实践，因为它清楚地显示了公共方法上的必填字段。|4032988|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|$]]

You can do it using contracts but it is the same concept. 

This should be good practise anyhow, because it clearly shows what are mandatory fields on a public method.

blocks|key|1577715|text|虽然Fluent+Argument+Validation没有内置到.Net框架中，但您可以使用它|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1577716|entityMap|0|LINK|mutability|MUTABLE|url|http://www.mrkwatkins.co.uk/Blog/2009/06/17/Fluent-Argument-Validation-Part-1---The-Competition^0|2|Q|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

It's not build into the .Net Framework but you can use <a href="http://www.mrkwatkins.co.uk/Blog/2009/06/17/Fluent-Argument-Validation-Part-1---The-Competition" rel="nofollow noreferrer">Fluent Argument Validation</a>

blocks|key|2624903|text|这样做的Here's+a+nice+fluent+way。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2624904|What+are+your+favorite+extension+methods+for+C#?+(codeplex.com/extensionoverflow)|2624905|public+static+class+Extensions
{
++++++++public+static+void+ThrowIfArgumentIsNull<T>(this+T+obj,+string+parameterName)+where+T+:+class
++++++++{
++++++++++++++++if+(obj+==+null)+throw+new+ArgumentNullException(parameterName+%2B+"+not+allowed+to+be+null");
++++++++}
}

internal+class+Test
{
++++++++public+Test(string+input1)
++++++++{
++++++++++++++++input1.ThrowIfArgumentIsNull("input1");
++++++++}
}|code-block|syntax|javascript|2624906|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/271398/what-are-your-favorite-extension-methods-for-c-codeplex-com-extensionoverflow/271409#271409|1^0|4|O|0|0|0|29|1|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]]|C|$]]|$1|D|3|E|5|6|7|X|8|@]|9|@$A|Y|B|Z|1|10]]|C|$]]|$1|F|3|G|5|H|7|11|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|12|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]|S|$5|N|O|P|C|$Q|R]]]]

<a href="https://stackoverflow.com/questions/271398/what-are-your-favorite-extension-methods-for-c-codeplex-com-extensionoverflow/271409#271409">Here's a nice fluent way</a> of doing this.

<a href="https://stackoverflow.com/questions/271398/what-are-your-favorite-extension-methods-for-c-codeplex-com-extensionoverflow/271409#271409">What are your favorite extension methods for C#? (codeplex.com/extensionoverflow)</a>

<pre><code>public static class Extensions
{
 public static void ThrowIfArgumentIsNull&lt;T&gt;(this T obj, string parameterName) where T : class
 {
 if (obj == null) throw new ArgumentNullException(parameterName + " not allowed to be null");
 }
}

internal class Test
{
 public Test(string input1)
 {
 input1.ThrowIfArgumentIsNull("input1");
 }
}
</code></pre>

blocks|key|828876|text|我通常创建静态帮助器方法...|type|unstyled|depth|inlineStyleRanges|entityRanges|data|828877|例如。|828878|public+static+void+CheckNotNull(object+value,+string+parameterName)
{
+++if(value+==+null)+{+throw+new+ArgumentNullException(parameterName);+}
}|code-block|syntax|javascript|828879|这意味着你可以把你的代码压缩成类似下面的东西，让它更整洁一点。|828880|CheckNotNull(username,+"username");
CheckNotNull(password,+"password");+|828881|或者，您可以将其包装为扩展方法：|828882|public+static+void+CheckNotNull<T>(this+T+value,+string+parameterName)
{
+++if(value+==+null)+{+throw+new+ArgumentNullException(parameterName);+}
}|828883|并像这样使用：|828884|username.CheckNotNull("username");
password.CheckNotNull("password");|828885|如果你真的觉得很花哨，你可以使用反射来询问参数名。反射有点慢，所以你只有在抛出异常的时候才会这么做，但它省去了你一直在输入文字参数名的时间。|828886|entityMap^0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|10|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|11|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|12|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|13|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|14|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|15|8|@]|9|@]|A|$]]|$1|S|3|T|5|F|7|16|8|@]|9|@]|A|$G|H]]|$1|U|3|V|5|6|7|17|8|@]|9|@]|A|$]]|$1|W|3|-4|5|6|7|18|8|@]|9|@]|A|$]]]|X|$]]

I normally create static helper methods...

E.g.

<pre><code>public static void CheckNotNull(object value, string parameterName)
{
 if(value == null) { throw new ArgumentNullException(parameterName); }
}
</code></pre>

Means you can condense your code down to something similar to below and just makes it a little tidier.

<pre><code>CheckNotNull(username, "username");
CheckNotNull(password, "password"); 
</code></pre>

Or you can wrap it up as an extension method:

<pre><code>public static void CheckNotNull&lt;T&gt;(this T value, string parameterName)
{
 if(value == null) { throw new ArgumentNullException(parameterName); }
}
</code></pre>

And use like:

<pre><code>username.CheckNotNull("username");
password.CheckNotNull("password");
</code></pre>

And if you're feeling really fancy, you could probably interrogate the parameter names by using reflection. Reflection's kinda slow, so you'd only do this if you were going to throw an exception, but it saves you typing the literal parameter name all the time.

blocks|key|2624996|text|类似于Giorgi提到的fluent参数验证的想法，但这一点避免了多余的参数命名，以及无法通过代码重构工具自动更新的字符串。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2624997|http://charlieflowers.wordpress.com/tag/parameter-validation/|offset|length|2624998|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|1P|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@$D|O|E|P|1|Q]]|A|$]]|$1|F|3|-4|5|6|7|R|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|C]]]]

Similar idea to fluent parameter validation as mentioned by Giorgi, but this one avoids redundantly naming the parameter, and the strings that can't be automatically updated by code refactoring tools.

<a href="http://charlieflowers.wordpress.com/tag/parameter-validation/" rel="nofollow noreferrer">http://charlieflowers.wordpress.com/tag/parameter-validation/</a>

blocks|key|831678|text|您可以使用像Post+Sharp这样的il编织器，请记住，在C#+5中，编译器作为一种服务将使这种东西成为内置的东西。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|831679|就我个人而言，我不推荐这种方法，除非问题很严重，必须解决。通常，像上面描述的那样执行一些断言和检查前提条件是一种最佳实践。|831680|例如：|831681|public+ConnectionSettings(
+++[NotNullOrEmpty]+string+url,+
+++[NotNull]+string+username,+
+++[NotNull]+string+password,
+++bool+checkPermissions)
{
++++this.url+=+url;
++++this.username+=+username;
++++this.password+=+password;
++++this.checkPermissions+=+checkPermissions;
}|code-block|syntax|javascript|831682|您还可以将这类内容与code+contracts集成，这将允许您执行一些丰富的静态分析。|831683|entityMap|0|LINK|mutability|MUTABLE|url|http://www.sharpcrafters.com/|1|http://msdn.microsoft.com/en-us/devlabs/dd491992.aspx^0|6|A|0|0|0|0|0|A|E|1|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]]|C|$]]|$1|D|3|E|5|6|7|12|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|13|8|@]|9|@]|C|$]]|$1|H|3|I|5|J|7|14|8|@]|9|@]|C|$K|L]]|$1|M|3|N|5|6|7|15|8|@]|9|@$A|16|B|17|1|18]]|C|$]]|$1|O|3|-4|5|6|7|19|8|@]|9|@]|C|$]]]|P|$Q|$5|R|S|T|C|$U|V]]|W|$5|R|S|T|C|$U|X]]]]

You could use an il weaver like <a href="http://www.sharpcrafters.com/" rel="nofollow noreferrer">Post Sharp</a>, keep in mind that compiler as a service in C# 5 will make this kind of stuff built in. 

Personally I would not recommend this approach unless the problem is huge and must be tackled. Usually a few asserts and checking preconditions as you described above is a best practice. 

EG: 

<pre><code>public ConnectionSettings(
 [NotNullOrEmpty] string url, 
 [NotNull] string username, 
 [NotNull] string password,
 bool checkPermissions)
{
 this.url = url;
 this.username = username;
 this.password = password;
 this.checkPermissions = checkPermissions;
}
</code></pre>

You could also integrate this kind of stuff with <a href="http://msdn.microsoft.com/en-us/devlabs/dd491992.aspx" rel="nofollow noreferrer">code contracts</a> which would allow you to perform some rich static analysis.

blocks|key|4033234|text|为了补充山姆上面的答案，这里有一个链接，告诉你如何使用PostSharp实现这些属性：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4033235|http://dpatrickcaldwell.blogspot.com/2009/03/validate-parameters-using-attributes.html|offset|length|4033236|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|2E|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@$D|O|E|P|1|Q]]|A|$]]|$1|F|3|-4|5|6|7|R|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|C]]]]

Just to add to Sam's answer above, here's a link which tells you how you can go about implementing such attributes with PostSharp:

<a href="http://dpatrickcaldwell.blogspot.com/2009/03/validate-parameters-using-attributes.html" rel="nofollow noreferrer">http://dpatrickcaldwell.blogspot.com/2009/03/validate-parameters-using-attributes.html</a>

blocks|key|2625128|text|我最近发布了Guard的第一个稳定版本，这是一个帮助您编写如下保护子句的库：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2625129|public+ConnectionSettings(
++++Uri+url,+string+username,+string+password,+bool+checkPermissions)
{
++++this.username+=+Guard.Argument(()+=>+username).NotNull();
++++this.password+=+Guard.Argument(()+=>+password).NotNull();
++++this.url+=+Guard.Argument(()+=>+url).NotNull().Https();
++++this.checkPermissions+=+checkPermissions;
}|code-block|syntax|javascript|2625130|2625131|它比你想象的要快，this+document深入研究了performance+this+document可以以扩展方法的形式添加新的验证，this+document详细解释了这一点。|unordered-list-item|2625132|2625133|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/safakgur/guard|1|https://github.com/safakgur/guard/blob/master/docs/design-decisions.md|2|https://github.com/safakgur/guard/blob/master/docs/extensibility.md|3^0|6|5|0|0|0|0|9|D|1|13|D|2|1X|D|3|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]]|C|$]]|$1|D|3|E|5|F|7|14|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|15|8|@]|9|@]|C|$]]|$1|J|3|K|5|L|7|16|8|@]|9|@$A|17|B|18|1|19]|$A|1A|B|1B|1|1C]|$A|1D|B|1E|1|1F]]|C|$]]|$1|M|3|-4|5|6|7|1G|8|@]|9|@]|C|$]]|$1|N|3|-4|5|6|7|1H|8|@]|9|@]|C|$]]]|O|$P|$5|Q|R|S|C|$T|U]]|V|$5|Q|R|S|C|$T|W]]|X|$5|Q|R|S|C|$T|Y]]|Z|$5|Q|R|S|C|$T|Y]]]]

I recently released the first stable version of <a href="https://github.com/safakgur/guard" rel="nofollow noreferrer">Guard</a>, a library that helps you write guard clauses like these:

<pre><code>public ConnectionSettings(
 Uri url, string username, string password, bool checkPermissions)
{
 this.username = Guard.Argument(() =&gt; username).NotNull();
 this.password = Guard.Argument(() =&gt; password).NotNull();
 this.url = Guard.Argument(() =&gt; url).NotNull().Https();
 this.checkPermissions = checkPermissions;
}
</code></pre>

<ul>
<li>It's faster than you may think, <a href="https://github.com/safakgur/guard/blob/master/docs/design-decisions.md" rel="nofollow noreferrer">this document</a> delves deeper into the performance considerations.</li>
<li>You can add new validations in the form of extension methods, <a href="https://github.com/safakgur/guard/blob/master/docs/extensibility.md" rel="nofollow noreferrer">this document</a> explains it in detail.</li>
</ul>

We use the .NET 2.0 framework with C# 3.0 (I think it's the last version of C# which can run on the 2.0 version of the framework, correct me if I am wrong).

Is there something built into C# which can make this type of parameter validation more convenient?

<pre><code>public ConnectionSettings(string url, string username, string password,
 bool checkPermissions)
{
 if (username == null) {
 throw new ArgumentNullException("username");
 }

 if (password == null) {
 throw new ArgumentNullException("password");
 }

 if (String.IsNullOrEmpty(url)) {
 throw new ArgumentException("Must not be null or empty, it was " +
 (url == null ? url : "empty"), "url");
 }

 this.url = url;
 this.username = username;
 this.password = password;
 this.checkPermissions = checkPermissions;
}
</code></pre>

That sort of parameter validation becomes a common pattern and results in a lot of "almost boilerplate" code to wade through in our public methods.

If there is nothing built in. Are there any great free libraries which we could use?

Nicer way of parameter checking?

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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我们使用.NET 2.0框架和C# 3.0 (我认为这是可以在2.0版本的框架上运行的C#的最后一个版本，如果我错了，请纠正我)。C#中有什么内置的东西可以让这种类型的参数验证更方便吗？public ConnectionSettings(string url, string username, string passw...

问更好的参数检查方式？
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问更好的参数检查方式？EN