如何动态评估 C# 表达式? [英] How can I evaluate a C# expression dynamically?

问题描述

我想做相当于:

object result = Eval("1 + 3");
string now    = Eval("System.DateTime.Now().ToString()") as string

在 Biri s link 之后，我得到了这个片段(修改以删除过时的方法 ICodeCompiler.CreateCompiler():

Following Biri s link, I got this snippet (modified to remove obsolete method ICodeCompiler.CreateCompiler():

private object Eval(string sExpression)
{
    CSharpCodeProvider c = new CSharpCodeProvider();
    CompilerParameters cp = new CompilerParameters();

    cp.ReferencedAssemblies.Add("system.dll");

    cp.CompilerOptions = "/t:library";
    cp.GenerateInMemory = true;

    StringBuilder sb = new StringBuilder("");
    sb.Append("using System;
");

    sb.Append("namespace CSCodeEvaler{ 
");
    sb.Append("public class CSCodeEvaler{ 
");
    sb.Append("public object EvalCode(){
");
    sb.Append("return " + sExpression + "; 
");
    sb.Append("} 
");
    sb.Append("} 
");
    sb.Append("}
");

    CompilerResults cr = c.CompileAssemblyFromSource(cp, sb.ToString());
    if (cr.Errors.Count > 0)
    {
        throw new InvalidExpressionException(
            string.Format("Error ({0}) evaluating: {1}", 
            cr.Errors[0].ErrorText, sExpression));
    }

    System.Reflection.Assembly a = cr.CompiledAssembly;
    object o = a.CreateInstance("CSCodeEvaler.CSCodeEvaler");

    Type t = o.GetType();
    MethodInfo mi = t.GetMethod("EvalCode");

    object s = mi.Invoke(o, null);
    return s;

}  

推荐答案

老话题，但考虑到这是谷歌搜索时出现的第一个线程，这里有一个更新的解决方案.

Old topic, but considering this is one of the first threads showing up when googling, here is an updated solution.

您可以使用 Roslyn 的新脚本 API 来计算表达式.

如果您使用的是 NuGet，只需将依赖项添加到 Microsoft.CodeAnalysis.CSharp.Scripting.要评估您提供的示例，很简单:

If you are using NuGet, just add a dependency to Microsoft.CodeAnalysis.CSharp.Scripting. To evaluate the examples you provided, it is as simple as:

var result = CSharpScript.EvaluateAsync("1 + 3").Result;

这显然没有利用脚本引擎的异步功能.

This obviously does not make use of the scripting engine's async capabilities.

您还可以根据需要指定评估结果类型:

You can also specify the evaluated result type as you intended:

var now = CSharpScript.EvaluateAsync<string>("System.DateTime.Now.ToString()").Result;

要评估更高级的代码片段、传递参数、提供引用、命名空间等，请查看上面链接的 wiki.

To evaluate more advanced code snippets, pass parameters, provide references, namespaces and whatnot, check the wiki linked above.

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