C#.NET 动态计算表达式值

 

  
    

   
     
   
     using
   
      System;

   
     using
   
      System.CodeDom.Compiler;

   
     using
   
      Microsoft.CSharp;

   
     using
   
      System.Reflection;


   
     namespace
   
      Pub.Class {
 
   
     ///
   
      
   
     <summary>
   
     
 
   
     ///
   
      处理表达试运算---动态生成数学表达式并计算其值
 
   
     ///
   
      表达式使用 C# 语法，可带一个的自变量(x)。
 
   
     ///
   
      表达式的自变量和值均为(double)类型。
 
   
     ///
   
      
   
     </summary>
   
     
 
   
     ///
   
      
   
     <example>
   
     
 
   
     ///
   
      
   
     <code>
   
     
 
   
     ///
   
      Expression expression = new Expression("Math.Sin(x)"); 
 
   
     ///
   
      Console.WriteLine(expression.Compute(Math.PI / 2)); 
 
   
     ///
   
      expression = new Expression("double u = Math.PI - x;" + 
 
   
     ///
   
      "double pi2 = Math.PI * Math.PI;" + 
 
   
     ///
   
      "return 3 * x * x + Math.Log(u * u) / pi2 / pi2 + 1;"); 
 
   
     ///
   
      Console.WriteLine(expression.Compute(0)); 
 
   
     ///
   
      
 
   
     ///
   
      Expression expression = new Expression("return 10*(5+5)/10;");
 
   
     ///
   
      Response.Write(expression.Compute(0));
 
   
     ///
   
      Response.End();
 
   
     ///
   
      
   
     </code>
   
     
 
   
     ///
   
      
   
     </example>
   
     

   
      
   
     public
   
      
   
     class
   
      Expression {
 
   
     object
   
      instance;
 MethodInfo method;
 
   
     ///
   
      
   
     <summary>
   
     
 
   
     ///
   
      表达试运算
 
   
     ///
   
      
   
     </summary>
   
     
 
   
     ///
   
      
   
     <param name="expression">
   
     表达试
   
     </param>
   
     

   
      
   
     public
   
      Expression(
   
     string
   
      expression) {
 
   
     if
   
      (expression.IndexOf(
   
     "
   
     return
   
     "
   
     ) 
   
     <
   
      
   
     0
   
     ) expression 
   
     =
   
      
   
     "
   
     return 
   
     "
   
      
   
     +
   
      expression 
   
     +
   
      
   
     "
   
     ;
   
     "
   
     ;
 
   
     string
   
      className 
   
     =
   
      
   
     "
   
     Expression
   
     "
   
     ;
 
   
     string
   
      methodName 
   
     =
   
      
   
     "
   
     Compute
   
     "
   
     ;
 CompilerParameters p 
   
     =
   
      
   
     new
   
      CompilerParameters();
 p.GenerateInMemory 
   
     =
   
      
   
     true
   
     ;
 CompilerResults cr 
   
     =
   
      
   
     new
   
      CSharpCodeProvider().CompileAssemblyFromSource(p, 
   
     string
   
     .
 Format(
   
     "
   
     using System;sealed class {0}{{public double {1}(double x){{{2}}}}}
   
     "
   
     ,
 className, methodName, expression));
 
   
     if
   
      (cr.Errors.Count 
   
     >
   
      
   
     0
   
     ) {
 
   
     string
   
      msg 
   
     =
   
      
   
     "
   
     Expression(\
   
     ""
   
      + expression + 
   
     "
   
     \
   
     "
   
     ): \n
   
     "
   
     ;
 
   
     foreach
   
      (CompilerError err 
   
     in
   
      cr.Errors) msg 
   
     +=
   
      err.ToString() 
   
     +
   
      
   
     "
   
     \n
   
     "
   
     ;
 
   
     throw
   
      
   
     new
   
      Exception(msg);
 }
 instance 
   
     =
   
      cr.CompiledAssembly.CreateInstance(className);
 method 
   
     =
   
      instance.GetType().GetMethod(methodName);
 }
 
   
     ///
   
      
   
     <summary>
   
     
 
   
     ///
   
      处理数据
 
   
     ///
   
      
   
     </summary>
   
     
 
   
     ///
   
      
   
     <param name="x"></param>
   
     
 
   
     ///
   
      
   
     <returns>
   
     返回计算值
   
     </returns>
   
     

   
      
   
     public
   
      
   
     double
   
      Compute(
   
     double
   
      x) {
 
   
     return
   
      (
   
     double
   
     )method.Invoke(instance, 
   
     new
   
      
   
     object
   
     [] { x });
 }
 }
}