C𞃳動的実行文字列(動的作成コード)

C〓〓のプログラムを編纂する時、私達は動態的にいくつかコードを生成して実行する必要があります.しかし、C〓〓はJavaScriptと違って、Eva関数があります.コードを動的に実行できます.これらの機能は全部自分で完成します.次のように実例を示します
動的作成コード:

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

namespace EvalGuy   
{   
    /// <summary>   
    ///                      
    ///      ，     ！   
    /// </summary>   
    public class Evaluator   
    { 
        #region        
        /// <summary>   
        ///             
        /// </summary>   
        /// <param name="items">   
        ///            
        /// </param>   
        public Evaluator(EvaluatorItem[] items)   
        {   
            ConstructEvaluator(items);      //                  
        }   
        /// <summary>   
        ///             
        /// </summary>   
        /// <param name="returnType">     </param>   
        /// <param name="expression">     </param>   
        /// <param name="name">       </param>   
        public Evaluator(Type returnType, string expression, string name)   
        {   
            //             
            EvaluatorItem[] items = { new EvaluatorItem(returnType, expression, name) };   
            ConstructEvaluator(items);      //                  
        }   
        /// <summary>   
        ///             
        /// </summary>   
        /// <param name="item">       </param>   
        public Evaluator(EvaluatorItem item)   
        {   
            EvaluatorItem[] items = { item };//                      
            ConstructEvaluator(items);      //                  
        }   
        /// <summary>   
        ///             
        /// </summary>   
        /// <param name="items">        </param>   
        private void ConstructEvaluator(EvaluatorItem[] items)   
        {   
            //  C#        
            ICodeCompiler comp = (new CSharpCodeProvider().CreateCompiler());   
            //           
            CompilerParameters cp = new CompilerParameters();   

            cp.ReferencedAssemblies.Add("system.dll");              //      system.dll       
            cp.ReferencedAssemblies.Add("system.data.dll");         //      system.data.dll       
            cp.ReferencedAssemblies.Add("system.xml.dll");          //      system.xml.dll       
            cp.GenerateExecutable = false;                          //           
            cp.GenerateInMemory = true;                             //         

            StringBuilder code = new StringBuilder();               //        
            /* 
             *               
             */ 
            code.Append("using System; 
");   
            code.Append("using System.Data; 
");   
            code.Append("using System.Data.SqlClient; 
");   
            code.Append("using System.Data.OleDb; 
");   
            code.Append("using System.Xml; 
");   

            code.Append("namespace EvalGuy { 
");                  //          EvalGuy，         

            code.Append(" public class _Evaluator { 
");          //   _Evaluator  ，                 
            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("}
");                                 //           
            }   
            code.Append("} }");                                 //                 

            //               
            CompilerResults cr = comp.CompileAssemblyFromSource(cp, code.ToString());   

            if (cr.Errors.HasErrors)                            //        
            {   
                StringBuilder error = new StringBuilder();          //            
                error.Append("         : ");                //         
                foreach (CompilerError err in cr.Errors)            //               
                {   
                    error.AppendFormat("{0}
", err.ErrorText);     //       ，          
                }   
                throw new Exception("    : " + error.ToString());//       
            }   
            Assembly a = cr.CompiledAssembly;                       //              
            _Compiled = a.CreateInstance("EvalGuy._Evaluator");     //           EvalGuy._Evaluator       
        } 
        #endregion 

        #region        
        /// <summary>   
        ///               
        /// </summary>   
        /// <param name="name">       </param>   
        /// <returns>    </returns>   
        public int EvaluateInt(string name)   
        {   
            return (int)Evaluate(name);   
        }   
        /// <summary>   
        ///                 
        /// </summary>   
        /// <param name="name">       </param>   
        /// <returns>    </returns>   
        public string EvaluateString(string name)   
        {   
            return (string)Evaluate(name);   
        }   
        /// <summary>   
        ///                
        /// </summary>   
        /// <param name="name">       </param>   
        /// <returns>    </returns>   
        public bool EvaluateBool(string name)   
        {   
            return (bool)Evaluate(name);   
        }   
        /// <summary>   
        ///         object      
        /// </summary>   
        /// <param name="name">       </param>   
        /// <returns>    </returns>   
        public object Evaluate(string name)   
        {   
            MethodInfo mi = _Compiled.GetType().GetMethod(name);//   _Compiled          name          
            return mi.Invoke(_Compiled, null);                  //   mi          
        } 
        #endregion 

        #region        
        /// <summary>   
        ///               
        /// </summary>   
        /// <param name="code">       </param>   
        /// <returns>    </returns>   
        static public int EvaluateToInteger(string code)   
        {   
            Evaluator eval = new Evaluator(typeof(int), code, staticMethodName);//   Evaluator        
            return (int)eval.Evaluate(staticMethodName);                        //            
        }   
        /// <summary>   
        ///                 
        /// </summary>   
        /// <param name="code">       </param>   
        /// <returns>    </returns>   
        static public string EvaluateToString(string code)   
        {   
            Evaluator eval = new Evaluator(typeof(string), code, staticMethodName);//   Evaluator        
            return (string)eval.Evaluate(staticMethodName);                     //              
        }   
        /// <summary>   
        ///                
        /// </summary>   
        /// <param name="code">       </param>   
        /// <returns>    </returns>   
        static public bool EvaluateToBool(string code)   
        {   
            Evaluator eval = new Evaluator(typeof(bool), code, staticMethodName);//   Evaluator        
            return (bool)eval.Evaluate(staticMethodName);                       //             
        }   
        /// <summary>   
        ///          object      
        /// </summary>   
        /// <param name="code">       </param>   
        /// <returns>    </returns>   
        static public object EvaluateToObject(string code)   
        {   
            Evaluator eval = new Evaluator(typeof(object), code, staticMethodName);//   Evaluator        
            return eval.Evaluate(staticMethodName);                             //      object       
        } 
        #endregion 

        #region        
        /// <summary>   
        ///                
        /// </summary>   
        private const string staticMethodName = "__foo";   
        /// <summary>   
        ///           ，                 
        /// </summary>   
        object _Compiled = null; 
        #endregion   
    }   
    /// <summary>   
    ///        （         ）   
    /// </summary>   
    public class EvaluatorItem   
    {   
        /// <summary>   
        ///         
        /// </summary>   
        public Type ReturnType;   
        /// <summary>   
        ///         
        /// </summary>   
        public string Expression;   
        /// <summary>   
        ///           
        /// </summary>   
        public string Name;   
        /// <summary>   
        ///               
        /// </summary>   
        /// <param name="returnType">     </param>   
        /// <param name="expression">     </param>   
        /// <param name="name">       </param>   
        public EvaluatorItem(Type returnType, string expression, string name)   
        {   
            ReturnType = returnType;   
            Expression = expression;   
            Name = name;   
        }   
    }   
}

 
呼び出し方法:EvaalGry名前空間を参照してください.

Console.WriteLine("Test0: {0}", Evaluator.EvaluateToInteger("(30 + 4) * 2"));   
Console.WriteLine("Test1: {0}", Evaluator.EvaluateToString("\"Hello \" + \"There\""));   
Console.WriteLine("Test2: {0}", Evaluator.EvaluateToBool("30 == 40"));   
Console.WriteLine("Test3: {0}", Evaluator.EvaluateToObject("new DataSet()"));   

EvaluatorItem[] items = {   
                          new EvaluatorItem(typeof(int), "(30 + 4) * 2", "GetNumber"),   
                          new EvaluatorItem(typeof(string), "\"Hello \" + \"There\"",    
                                                            "GetString"),   
                          new EvaluatorItem(typeof(bool), "30 == 40", "GetBool"),   
                          new EvaluatorItem(typeof(object), "new DataSet()", "GetDataSet")   
                        };   

Evaluator eval = new Evaluator(items);   
Console.WriteLine("TestStatic0: {0}", eval.EvaluateInt("GetNumber"));   
Console.WriteLine("TestStatic1: {0}", eval.EvaluateString("GetString"));   
Console.WriteLine("TestStatic2: {0}", eval.EvaluateBool("GetBool"));   
Console.WriteLine("TestStatic3: {0}", eval.Evaluate("GetDataSet"));

 
回転:http://hi.baidu.com/yxw740/item/e4d256f2208590d342c36acc