blocks|key|455748|text|基本上你不能。CLR类型系统不支持这种约束。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|455749|我以前曾在博客中提到过如何使用“静态接口”来描述这些约束，但我不知道有任何类似的计划。|offset|length|455750|您可能想看看MiscUtil泛型运算符支持，它允许您使用操作符--但是您必须使用struct之类的约束，这当然允许您不想要的Guid之类的东西。|style|CODE|455751|entityMap|0|LINK|mutability|MUTABLE|url|http://msmvps.com/blogs/jon_skeet/archive/2008/08/29/lessons-learned-from-protocol-buffers-part-4-static-interfaces.aspx|1|http://www.yoda.arachsys.com/csharp/miscutil/usage/genericoperators.html^0|0|F|6|0|0|14|6|1Q|4|6|F|1|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|U|8|@]|9|@$D|V|E|W|1|X]]|A|$]]|$1|F|3|G|5|6|7|Y|8|@$D|Z|E|10|H|I]|$D|11|E|12|H|I]]|9|@$D|13|E|14|1|15]]|A|$]]|$1|J|3|-4|5|6|7|16|8|@]|9|@]|A|$]]]|K|$L|$5|M|N|O|A|$P|Q]]|R|$5|M|N|O|A|$P|S]]]]

You can't, basically. The CLR type system doesn't support that kind of constraint.

I've previous blogged about how we could describe such constraints using <a href="http://msmvps.com/blogs/jon_skeet/archive/2008/08/29/lessons-learned-from-protocol-buffers-part-4-static-interfaces.aspx" rel="nofollow noreferrer">"static interfaces"</a> but I don't know of any plans to do anything similar.

You might want to look at the <a href="http://www.yoda.arachsys.com/csharp/miscutil/usage/genericoperators.html" rel="nofollow noreferrer">MiscUtil generic operator support</a> which would let you use the operators - but you'd have to use a constraint of just <code>struct</code> or something like that, which would of course allow things like <code>Guid</code> which you don't want.

blocks|key|1653488|text|最接近的匹配是值类型约束。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1653489|C#只允许三种类型的约束|1653490|推导约束|ordered-list-item|1653491|构造函数|1653492|引用/值类型。|1653493|有关完整的文档，请参阅MSDN：|1653494|topic4|offset|length|1653495|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/ms379564(VS.80).aspx#csharp_generics_topic4^0|0|0|0|0|0|0|0|6|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|10|8|@]|9|@]|A|$]]|$1|G|3|H|5|F|7|11|8|@]|9|@]|A|$]]|$1|I|3|J|5|F|7|12|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|13|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|14|8|@]|9|@$O|15|P|16|1|17]]|A|$]]|$1|Q|3|-4|5|6|7|18|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]]]

The closest match is value type constrain.

C# allows only three types of constrains 

<ol>
<li>Derivation Constrain </li>
<li>Constructor </li>
<li>Reference/Value type. </li>
</ol>

For complete documentation refer MSDN: 
<a href="http://msdn.microsoft.com/en-us/library/ms379564(VS.80).aspx#csharp_generics_topic4" rel="nofollow noreferrer">http://msdn.microsoft.com/en-us/library/ms379564(VS.80).aspx#csharp_generics_topic4</a>

blocks|key|2008527|text|您可以使用一个解决方案:为您想要支持的每个类型定义一个方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2008528|private+static+Add(float+a,+float+b)+
{return+a%2Bb;}++
private+static+Add(double+a,+double+b)+
{return+a%2Bb;}++
...|code-block|syntax|javascript|2008529|并在运行时为正确的委托创建一个委托：|2008530|MethodInfo+addMethod=this.GetType().GetMethod("Add",BindingFlags.NotPublic%7CStatic,null,new+Type[2]{typeof(T),typeof(T)},null);++
Func<T,T,T>+addFunction=(Func<T,T,T>)Delegate.CreateDelegate(typeof(Func<T,T,T>),addMethod);|2008531|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

You could use a workaround: Define a method for every type you want to suport

<pre><code>private static Add(float a, float b) 
{return a+b;} 
private static Add(double a, double b) 
{return a+b;} 
...
</code></pre>

and create a delegate for the right one at runtime:

<pre><code>MethodInfo addMethod=this.GetType().GetMethod("Add",BindingFlags.NotPublic|Static,null,new Type[2]{typeof(T),typeof(T)},null); 
Func&lt;T,T,T&gt; addFunction=(Func&lt;T,T,T&gt;)Delegate.CreateDelegate(typeof(Func&lt;T,T,T&gt;),addMethod);
</code></pre>

blocks|key|455814|text|这通常是一个严重的错误，但您可以为数字类型创建一个通用的“包装器”类，该类公开所需的操作，并防止使用不受支持的值类型(即char)实例化，然后指定算法的泛型类型参数必须是包装类。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|455815|除了代码复制之外，我喜欢Floste在各个方面的解决方案。您甚至可以简化它；指定私有方法重载，然后一个简单调用私有方法的公共泛型方法，运行时将选择正确的方法(确保包含抛出NotImplementedException的catch-all+)。|455816|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|$]]

This is generally a seriously fugly hack, but you can create a generic "wrapper" class for numeric types that exposes the operations you need and prevents instantiation using a non-supported value type (i.e. char), and then specify that the generic type parameter of your algorithm must be the wrapper class.

I like the workaround Floste posed in every respect except code duplication. You could even make it simpler; specify private method overloads, then one public generic method that will simply call the private method, and the runtime will pick the correct one (be sure to include a catch-all that throws a NotImplementedException).

<blockquote>
 Possible Duplicate: 
 <a href="https://stackoverflow.com/questions/3598341/define-a-generic-that-implements-the-operator">Define a generic that implements the + operator</a> 
</blockquote>



I am recently working on a C# class library implementing an algorithm. The point is that I would like the users of the library to be able to choose the machine precision (single or double) the algorithm should operate with, and I'm trying to do it with generics. So, for instance:

<pre><code> Algorithm&lt;double&gt; a = new Algorithm&lt;double&gt;();
 /** Some initializations here */
 double result = a.Solve();
</code></pre>

or

<pre><code> Algorithm&lt;float&gt; a = new Algorithm&lt;float&gt;();
 /** Some initializations here */
 float result = a.Solve();
</code></pre>

Thus, the type parameter for the generic classes is meant to be a decimal number (because in the algorithm code I need to use +, *, /, -), but I don't know which kind of type constraint to impose on it. I have thought about building an interface with all the operators but, unfortunately, this is not allowed. Any ideas?

Otherwise, is it possible to obtain in C# something similar to <a href="http://www.cprogramming.com/tutorial/template_specialization.html" rel="nofollow noreferrer">template specialization</a> in C++?

Thank you

Tommaso

How to impose, in a C# generic type parameter, that some operators are supported?

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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可能重复：最近，我正在开发一个实现算法的C#类库。关键是，我希望库的用户能够选择算法应该使用的机器精度(单精度或双精度)，我正在尝试使用泛型。因此，例如： Algorithm<double> a = new Algorithm<double>(); /** Some initializations here...

问如何在C#泛型参数中强制某些运算符受到支持？
EN

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问如何在C#泛型参数中强制某些运算符受到支持？EN