blocks|key|3089347|text|这当然是有可能的。CodeSnippetCompileUnit类基本上做到了这一点。我给你写了一些示例用法代码。您需要包含以下名称空间：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3089348|3089349|System.CodeDom.Compiler;|unordered-list-item|3089350|System.CodeDom;|3089351|Microsoft.CSharp;|3089352|System.Reflection;|3089353|3089354|代码如下：|3089355|string+source+=+@"
class+MyType
{
++++public+static+int+Evaluate(<!parameters!>)
++++{
++++++++return+<!expression!>;
++++}
}
";

string+parameters+=+"int+a,+int+b,+int+c";
string+expression+=+"a+%2B+b+*+c";

string+finalSource+=+source.Replace("<!parameters!>",+parameters).Replace("<!expression!>",+expression);

CodeSnippetCompileUnit+compileUnit+=+new+CodeSnippetCompileUnit(finalSource);
CodeDomProvider+provider+=+new+CSharpCodeProvider();

CompilerParameters+parameters+=+new+CompilerParameters();

CompilerResults+results+=+provider.CompileAssemblyFromDom(parameters,+compileUnit);

Type+type+=+results.CompiledAssembly.GetType("MyType");
MethodInfo+method+=+type.GetMethod("Evaluate");

//+The+first+parameter+is+the+instance+to+invoke+the+method+on.+Because+our+Evaluate+method+is+static,+we+pass+null.
int+result+=+(int)method.Invoke(null,+new+object[]+{+4,+-3,+2+});|code-block|syntax|javascript|3089356|将'parameters‘和'+expression’替换成任何东西，你就得到了一个通用的表达式求值器。|3089357|如果在results.CompiledAssembly中获得FileNotFoundException，则代码片段无法编译。|3089358|您可能还想看看System.CodeDom.CodeSnippetExpression类。它用于更具体地读取表达式，但是表达式本身不能被编译，因此您需要使用更多的CodeDom来围绕它构建一个工作类和方法。如果您希望能够以编程方式操作要生成的类，这将非常有用。CodeSnippetCompileUnit一次生成整个工作类是很好的(对于示例来说更简单)，但是要操作它，您必须进行不方便的字符串操作。|3089359|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/system.codedom.codesnippetcompileunit.aspx^0|9|M|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|19|8|@]|9|@$A|1A|B|1B|1|1C]]|C|$]]|$1|D|3|-4|5|6|7|1D|8|@]|9|@]|C|$]]|$1|E|3|F|5|G|7|1E|8|@]|9|@]|C|$]]|$1|H|3|I|5|G|7|1F|8|@]|9|@]|C|$]]|$1|J|3|K|5|G|7|1G|8|@]|9|@]|C|$]]|$1|L|3|M|5|G|7|1H|8|@]|9|@]|C|$]]|$1|N|3|-4|5|6|7|1I|8|@]|9|@]|C|$]]|$1|O|3|P|5|6|7|1J|8|@]|9|@]|C|$]]|$1|Q|3|R|5|S|7|1K|8|@]|9|@]|C|$T|U]]|$1|V|3|W|5|6|7|1L|8|@]|9|@]|C|$]]|$1|X|3|Y|5|6|7|1M|8|@]|9|@]|C|$]]|$1|Z|3|10|5|6|7|1N|8|@]|9|@]|C|$]]|$1|11|3|-4|5|6|7|1O|8|@]|9|@]|C|$]]]|12|$13|$5|14|15|16|C|$17|18]]]]

It's certainly possible. The <a href="http://msdn.microsoft.com/en-us/library/system.codedom.codesnippetcompileunit.aspx" rel="noreferrer">CodeSnippetCompileUnit</a> class does basically this.
I wrote you some example usage code. You'll need to include these namespaces:

<ul>
<li>System.CodeDom.Compiler;</li>
<li>System.CodeDom;</li>
<li>Microsoft.CSharp;</li>
<li>System.Reflection;</li>
</ul>

Here's the code:

<pre><code>string source = @"
class MyType
{
 public static int Evaluate(&lt;!parameters!&gt;)
 {
 return &lt;!expression!&gt;;
 }
}
";

string parameters = "int a, int b, int c";
string expression = "a + b * c";

string finalSource = source.Replace("&lt;!parameters!&gt;", parameters).Replace("&lt;!expression!&gt;", expression);

CodeSnippetCompileUnit compileUnit = new CodeSnippetCompileUnit(finalSource);
CodeDomProvider provider = new CSharpCodeProvider();

CompilerParameters parameters = new CompilerParameters();

CompilerResults results = provider.CompileAssemblyFromDom(parameters, compileUnit);

Type type = results.CompiledAssembly.GetType("MyType");
MethodInfo method = type.GetMethod("Evaluate");

// The first parameter is the instance to invoke the method on. Because our Evaluate method is static, we pass null.
int result = (int)method.Invoke(null, new object[] { 4, -3, 2 });
</code></pre>

Replace 'parameters' and 'expression' by whatever, and you've got yourself a general expression evaluator.

If you get a FileNotFoundException in results.CompiledAssembly, then the snippet failed to compile.

You might also want to take a look at the System.CodeDom.CodeSnippetExpression class. It's used for more specifically reading expressions, but an expression by itself can't be compiled, so you would need to use more CodeDom to build a working class and method around it. This is useful if you want to be able to programmatically manipulate what kind of class you're generating. CodeSnippetCompileUnit is nice to generate an entire working class at once (and simpler for an example) but to manipulate it you would have to do inconvenient string manipulations.

blocks|key|328514|text|尽管使用编译器服务是一种简单而有效的解决方案，但如果表达式是由用户输入的，则会带来严重的安全问题，因为它几乎可以执行任何事情。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|328515|还有另一个更安全的非常简单的解决方案:利用JScript+Eval函数。您只需要执行以下步骤：|offset|length|style|CODE|328516|创建一个名为JsMath.js的js文件：|328517|class+JsMath
{
++++static+function+Eval(expression+:+String)+:+double
++++{
++++++++return+eval(expression);
++++};
}|code-block|syntax|javascript|328518|将其编译成类库：|328519|jsc+/t:library+JsMath.js|328520|在C#项目中引用JsMath库，并像这样使用它：|328521|double+result+=+JsMath.Eval(expression);|328522|entityMap^0|0|T|4|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@$D|10|E|11|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|12|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|13|8|@]|9|@]|A|$M|N]]|$1|O|3|P|5|6|7|14|8|@]|9|@]|A|$]]|$1|Q|3|R|5|L|7|15|8|@]|9|@]|A|$M|N]]|$1|S|3|T|5|6|7|16|8|@]|9|@]|A|$]]|$1|U|3|V|5|L|7|17|8|@]|9|@]|A|$M|N]]|$1|W|3|-4|5|6|7|18|8|@]|9|@]|A|$]]]|X|$]]

Although using compiler services is a simple and efficient solution, it raises serious security issues if the expression is entered by a user, because it could execute virtually anything.

There's another very simple solution that is much more secure : take advantage of the JScript <code>Eval</code> function. You just need to follow these steps :

Create a js file named JsMath.js :

<pre><code>class JsMath
{
 static function Eval(expression : String) : double
 {
 return eval(expression);
 };
}
</code></pre>

Compile it into a class library :

<pre><code>jsc /t:library JsMath.js
</code></pre>

Reference the JsMath library in your C# project, and use it like that :

<pre><code>double result = JsMath.Eval(expression);
</code></pre>

blocks|key|333417|text|对我来说，Vici.Parser工作得非常好：check+it+out+here，它是迄今为止我发现的最灵活的表达式解析器。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|333418|(我们已经使用它来设置“人类可读的”业务规则，数据由SQL服务器数据库提供)|333419|示例是可用的，并且开发人员提供了非常好的支持(请查看网站的论坛)。|333420|entityMap|0|LINK|mutability|MUTABLE|url|http://viciproject.com/wiki/projects/parser/home^0|N|H|0|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|U|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|I|$J|$5|K|L|M|C|$N|O]]]]

For me Vici.Parser works extremely well: <a href="http://viciproject.com/wiki/projects/parser/home" rel="nofollow noreferrer">check it out here</a> , it's the most flexible expression parser I've found so far. 

(we've used it to set up 'human-readable' business rules, with data provided by an SQL server database)

Examples are available and there's a very good support by the developer (check the website's forum).

blocks|key|3089417|text|根据Thomas的回答，实际上可以直接从C#访问(不推荐使用的)+JScript库，这意味着您可以使用与JScript的eval函数等效的函数。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3089418|using+Microsoft.JScript;++++++++//+needs+a+reference+to+Microsoft.JScript.dll
using+Microsoft.JScript.Vsa;++++//+needs+a+reference+to+Microsoft.Vsa.dll

//+...

string+expr+=+"7+%2B+(5+*+4)";
Console.WriteLine(JScriptEval(expr));++++//+displays+27

//+...

public+static+double+JScriptEval(string+expr)
{
++++//+error+checking+etc+removed+for+brevity
++++return+double.Parse(Eval.JScriptEvaluate(expr,+_engine).ToString());
}

private+static+readonly+VsaEngine+_engine+=+VsaEngine.CreateEngine();|code-block|syntax|javascript|3089419|entityMap^0|1O|4|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Further to Thomas's answer, it's actually possible to access the (deprecated) JScript libraries directly from C#, which means you can use the equivalent of JScript's <code>eval</code> function.

<pre><code>using Microsoft.JScript; // needs a reference to Microsoft.JScript.dll
using Microsoft.JScript.Vsa; // needs a reference to Microsoft.Vsa.dll

// ...

string expr = "7 + (5 * 4)";
Console.WriteLine(JScriptEval(expr)); // displays 27

// ...

public static double JScriptEval(string expr)
{
 // error checking etc removed for brevity
 return double.Parse(Eval.JScriptEvaluate(expr, _engine).ToString());
}

private static readonly VsaEngine _engine = VsaEngine.CreateEngine();
</code></pre>

blocks|key|331190|text|ncalc是最好的。你可以在codeplex中找到它，也可以在nugget中找到它。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|331191|NCalc是.NET中的一个数学表达式求值器。NCalc可以解析任何表达式并计算结果，包括静态或动态参数和自定义函数。|331192|entityMap|0|LINK|mutability|MUTABLE|url|http://ncalc.codeplex.com/|1^0|0|5|0|E|8|1|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@$A|P|B|Q|1|R]|$A|S|B|T|1|U]]|C|$]]|$1|D|3|E|5|6|7|V|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|W|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|M]]]]

<a href="http://ncalc.codeplex.com/" rel="nofollow">ncalc</a> is the best. you can find it in <a href="http://ncalc.codeplex.com/" rel="nofollow">codeplex</a> also in nugget. 
NCalc is a mathematical expressions evaluator in .NET. NCalc can parse any expression and evaluate the result, including static or dynamic parameters and custom functions.

blocks|key|3302431|text|我认为这是最好的方式。Petar+Repac's+answer令人惊叹。使用DataColumn对象的'expression‘参数可以非常容易地解决这个问题：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3302432|static+double+Evaluate(string+expression)
{
++++var+loDataTable+=+new+DataTable();
++++var+loDataColumn+=+new+DataColumn("Eval",+typeof(double),+expression);
++++loDataTable.Columns.Add(loDataColumn);
++++loDataTable.Rows.Add(0);
++++return+(double)(loDataTable.Rows[0]["Eval"]);
}|code-block|syntax|javascript|3302433|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/333737/c-sharp-evaluating-string-342-yield-int-18^0|B|K|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

I think this is the best way of all. <a href="https://stackoverflow.com/questions/333737/c-sharp-evaluating-string-342-yield-int-18">Petar Repac's answer</a> is amazing.
Using the 'expression' argument of the DataColumn object solves incredibly and easily the topic:

<pre><code>static double Evaluate(string expression)
{
 var loDataTable = new DataTable();
 var loDataColumn = new DataColumn("Eval", typeof(double), expression);
 loDataTable.Columns.Add(loDataColumn);
 loDataTable.Rows.Add(0);
 return (double)(loDataTable.Rows[0]["Eval"]);
}
</code></pre>

blocks|key|331221|text|您可以使用Math-Expression-Evaluator库，它实现了我的作者之一的分流堆场算法。它支持简单的表达式，如2.5%2B5.9、17.89-2.47%2B7.16、5/2/2%2B1.5*3%2B4.58、带括号的表达式(((9-6/2)*2-4)/2-6-1)/(2%2B24/(2%2B4))和带变量的表达式：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|331222|var+a+=+6;
var+b+=+4.32m;
var+c+=+24.15m;
var+engine+=+new+ExpressionEvaluator();
engine.Evaluate("(((9-a/2)*2-b)/2-a-1)/(2%2Bc/(2%2B4))",+new+{+a,+b,+c});|code-block|syntax|javascript|331223|您还可以将参数作为命名变量进行传递：|331224|dynamic+dynamicEngine+=+new+ExpressionEvaluator();

var+a+=+6;
var+b+=+4.5m;
var+c+=+2.6m;

dynamicEngine.Evaluate("(c%2Bb)*a",+a:+6,+b:+4.5,+c:+2.6);|331225|它支持.Net标准2.0，因此可以在.Net核心以及.Net完整框架项目中使用，并且它没有任何外部依赖。|331226|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/Giorgi/Math-Expression-Evaluator^0|1P|7|1X|F|2D|G|31|Y|5|P|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@$9|17|A|18|1|19]]|E|$]]|$1|F|3|G|5|H|7|1A|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1B|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|1C|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1D|8|@]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|1E|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]]]

You can use <a href="https://github.com/Giorgi/Math-Expression-Evaluator" rel="nofollow noreferrer">Math-Expression-Evaluator</a> library which implements Shunting Yard algorithm that I am author of. It supports simple expressions such as <code>2.5+5.9</code>, <code>17.89-2.47+7.16</code>, <code>5/2/2+1.5*3+4.58</code>, expressions with parentheses <code>(((9-6/2)*2-4)/2-6-1)/(2+24/(2+4))</code> and expressions with variables:

<pre><code>var a = 6;
var b = 4.32m;
var c = 24.15m;
var engine = new ExpressionEvaluator();
engine.Evaluate("(((9-a/2)*2-b)/2-a-1)/(2+c/(2+4))", new { a, b, c});
</code></pre>

You can also pass parameters as named variables:

<pre><code>dynamic dynamicEngine = new ExpressionEvaluator();

var a = 6;
var b = 4.5m;
var c = 2.6m;

dynamicEngine.Evaluate("(c+b)*a", a: 6, b: 4.5, c: 2.6);
</code></pre>

It supports .Net Standard 2.0 so can be used from .Net Core as well as .Net Full Framework projects and it doesn't have any external dependencies.

blocks|key|331233|text|使用新的Roslyn+API动态编译代码，并将程序集加载到.net核心项目中；|type|unstyled|depth|inlineStyleRanges|entityRanges|data|331234|++++string+finalSource+=+...;
++++IEnumerable<Assembly>+references+=+...;

++++var+compilation+=+CSharpCompilation.Create("Dynamic",
++++++++new[]+{+
++++++++++++SyntaxFactory.ParseSyntaxTree(
++++++++++++++++finalSource,
++++++++++++++++CSharpParseOptions.Default
++++++++++++++++++++.WithLanguageVersion(LanguageVersion.Latest)
++++++++++++)+},
++++++++references.Select(a+=>+MetadataReference.CreateFromFile(a.Location)),

++++++++new+CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary)
++++++++++++.WithAssemblyIdentityComparer(DesktopAssemblyIdentityComparer.Default)
++++);

++++using+var+ms+=+new+MemoryStream();
++++var+e+=+compilation.Emit(ms);
++++if+(!e.Success)
++++++++throw+new+Exception("Compilation+failed");
++++ms.Seek(0,+SeekOrigin.Begin);

++++var+context+=+new+AssemblyLoadContext(null,+true);
++++var+assembly+=+context.LoadFromStream(ms);|code-block|syntax|javascript|331235|请注意，以及您正在编译的源代码所需的任何其他类型。为了在同一进程中加载已编译的程序集，引用将需要包括；|331236|++++AppDomain.CurrentDomain.GetAssemblies().Where(a+=>+a.GetName().Name+==+"netstandard").Single(),
++++typeof(object).Assembly|331237|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|$]]

To dynamically compile code using the new Roslyn API's, and load the assembly in a .net core project;

<pre class="lang-cs prettyprint-override"><code> string finalSource = ...;
 IEnumerable&lt;Assembly&gt; references = ...;

 var compilation = CSharpCompilation.Create("Dynamic",
 new[] { 
 SyntaxFactory.ParseSyntaxTree(
 finalSource,
 CSharpParseOptions.Default
 .WithLanguageVersion(LanguageVersion.Latest)
 ) },
 references.Select(a =&gt; MetadataReference.CreateFromFile(a.Location)),

 new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary)
 .WithAssemblyIdentityComparer(DesktopAssemblyIdentityComparer.Default)
 );

 using var ms = new MemoryStream();
 var e = compilation.Emit(ms);
 if (!e.Success)
 throw new Exception("Compilation failed");
 ms.Seek(0, SeekOrigin.Begin);

 var context = new AssemblyLoadContext(null, true);
 var assembly = context.LoadFromStream(ms);
</code></pre>

Note that along with any other types required by the source you are compiling. In order to load the compiled assembly within the same process, references will need to include;

<pre class="lang-cs prettyprint-override"><code> AppDomain.CurrentDomain.GetAssemblies().Where(a =&gt; a.GetName().Name == "netstandard").Single(),
 typeof(object).Assembly
</code></pre>

There are many algorithms to evaluate expressions, for example:

<ol>
<li><a href="http://www.engr.mun.ca/~theo/Misc/exp_parsing.htm" rel="noreferrer">By Recursive Descent</a> </li>
<li><a href="http://en.wikipedia.org/wiki/Shunting_yard_algorithm" rel="noreferrer">Shunting-yard algorithm</a></li>
<li><a href="http://en.wikipedia.org/wiki/Reverse_Polish_notation" rel="noreferrer">Reverse Polish notation</a></li>
</ol>

Is there any way to evaluate any mathematical expression using C# .net reflection or other modern .net technology?

Best and shortest way to evaluate mathematical expressions

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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计算表达式的算法有很多，例如： 有没有办法使用C#、.net反射或其他现代.net技术来计算任何数学表达式？

问计算数学表达式的最佳和最短方法
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