c#解析类 Evaluator 实现动态流程

最新推荐文章于 2021-07-01 17:23:32 发布

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最新推荐文章于 2021-07-01 17:23:32 发布

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分类专栏： c#技巧 .NET 文章标签： c# string object class assembly exception

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这个叫Evaluator的类，可以实现你的功能。
使用方法：Console.WriteLine("Test0: {0}", Evaluator.EvaluateToInteger("(30 + 4) * 2"));

using System;
using System.CodeDom;
using System.CodeDom.Compiler;
using Microsoft.CSharp;
using System.Text;
using System.Reflection;

namespace ADOGuy
{
/// <summary>
/// Summary description for Class1.
/// </summary>
public class Evaluator
{
    #region Construction
  public Evaluator(EvaluatorItem[] items)
  {
      ConstructEvaluator(items);
  }

    public Evaluator(Type returnType, string expression, string name)
    {
      EvaluatorItem[] items = { new EvaluatorItem(returnType, expression, name) };
      ConstructEvaluator(items);
    }

    public Evaluator(EvaluatorItem item)
    {
      EvaluatorItem[] items = { item };
      ConstructEvaluator(items);
    }

    private void ConstructEvaluator(EvaluatorItem[] items)
    {
      ICodeCompiler comp = (new CSharpCodeProvider().CreateCompiler());
      CompilerParameters cp = new CompilerParameters();
      cp.ReferencedAssemblies.Add("system.dll");
      cp.ReferencedAssemblies.Add("system.data.dll");
      cp.ReferencedAssemblies.Add("system.xml.dll");
      cp.GenerateExecutable = false;
      cp.GenerateInMemory = true;

      StringBuilder code = new StringBuilder();
      code.Append("using System; /n");
      code.Append("using System.Data; /n");
      code.Append("using System.Data.SqlClient; /n");
      code.Append("using System.Data.OleDb; /n");
      code.Append("using System.Xml; /n");
      code.Append("namespace ADOGuy { /n");
      code.Append(" public class _Evaluator { /n");
      foreach(EvaluatorItem item in items)
      {
        code.AppendFormat("    public {0} {1}() ",
                          item.ReturnType.Name,
                          item.Name);
        code.Append("{ ");
        code.AppendFormat("      return ({0}); ", item.Expression);
        code.Append("}/n");
      }
      code.Append("} }");

      CompilerResults cr = comp.CompileAssemblyFromSource(cp, code.ToString());
      if (cr.Errors.HasErrors)
      {
        StringBuilder error = new StringBuilder();
        error.Append("Error Compiling Expression: ");
        foreach (CompilerError err in cr.Errors)
        {
          error.AppendFormat("{0}/n", err.ErrorText);
        }
        throw new Exception("Error Compiling Expression: " + error.ToString());
      }
      Assembly a = cr.CompiledAssembly;
      _Compiled = a.CreateInstance("ADOGuy._Evaluator");
    }
    #endregion

    #region Public Members
    public int EvaluateInt(string name)
    {
      return (int) Evaluate(name);
    }

    public string EvaluateString(string name)
    {
      return (string) Evaluate(name);
    }

    public bool EvaluateBool(string name)
    {
      return (bool) Evaluate(name);
    }

    public object Evaluate(string name)
    {
      MethodInfo mi = _Compiled.GetType().GetMethod(name);
      return mi.Invoke(_Compiled, null);
    }
    #endregion

    #region Static Members
    static public int EvaluateToInteger(string code)
    {
      Evaluator eval = new Evaluator(typeof(int), code, staticMethodName);
      return (int) eval.Evaluate(staticMethodName);
    }

    static public string EvaluateToString(string code)
    {
      Evaluator eval = new Evaluator(typeof(string), code, staticMethodName);
      return (string) eval.Evaluate(staticMethodName);
    }

    static public bool EvaluateToBool(string code)
    {
      Evaluator eval = new Evaluator(typeof(bool), code, staticMethodName);
      return (bool) eval.Evaluate(staticMethodName);
    }

    static public object EvaluateToObject(string code)
    {
      Evaluator eval = new Evaluator(typeof(object), code, staticMethodName);
      return eval.Evaluate(staticMethodName);
    }
    #endregion

    #region Private
    const string staticMethodName = "__foo";
    Type _CompiledType = null;
    object _Compiled = null;
    #endregion
}

public class EvaluatorItem
{
    public EvaluatorItem(Type returnType, string expression, string name)
    {
      ReturnType = returnType;
      Expression = expression;
      Name = name;
    }

    public Type ReturnType;
    public string Name;
    public string Expression;
}
}