Sample: Dynamically Creating Code at Runtime and Calling from your Program

This is a small sample that shows how you can build code at runtime and generate an assembly to execute code which could be defined in a database or something. This example shows how to dynamically create a class that add the values of 2 numbers via the expression =Convert.ToInt32(a) + Convert.ToInt32(b).

using System;

using System.CodeDom.Compiler;

using System.Collections.Generic;

using System.Globalization;

using System.Reflection;

using System.Text;

using Microsoft.CSharp;

namespace ExpressionTest

{

  class Program

  {

    static void Main(string[] args)

    {      

      List<KeyValuePair<string, string>> properties = new List<KeyValuePair<string, string>>();

      properties.Add(new KeyValuePair<string, string>("a", "1"));

      properties.Add(new KeyValuePair<string, string>("b", "200"));

      string expression = "=Convert.ToInt32(a) + Convert.ToInt32(b)";

      string className = "Expression1";

      string methodName = "GetSum";

      string namespaceName = "ExpressionTest";

      //Create a Class

      StringBuilder _class = new StringBuilder();

      //Start Usings

      _class.Append("using System;\r\n");

      //Start Namespace

      _class.AppendFormat("namespace {0} {{\r\n", namespaceName);

      //Start Class

      _class.AppendFormat("public class {0} {{\r\n", className);

      //Start Properties

      foreach (KeyValuePair<string, string> p in properties)

      {

        _class.AppendFormat("public string {0};\r\n", p.Key);

      }

      //Start Constructor

      _class.AppendFormat("public {0} () {{\r\n", className);

      foreach (KeyValuePair<string, string> p in properties)

      {

        _class.AppendFormat("{0}=\"{1}\";\r\n", p.Key, p.Value);

      }      

      //End Constructor

      _class.Append("}\r\n");

      //Start Expression

      _class.AppendFormat("public string {0}() {{\r\n", methodName);

      if (expression.StartsWith("="))

      {

        _class.AppendFormat("return Convert.ToString({0});\r\n", expression.Substring(1));

      }

      //End Expression

      _class.Append("}\r\n");

      //End Class

      _class.Append("}\r\n");

      //End Namespace

      _class.Append("}\r\n");

      //Compile the Class

      CompilerParameters options = new CompilerParameters();

      options.GenerateInMemory = true;

      options.GenerateExecutable = false;

      foreach (AssemblyName assembly in typeof(Program).Assembly.GetReferencedAssemblies())

      {

        options.ReferencedAssemblies.Add(string.Format("{0}.dll", assembly.Name));

      }

      CSharpCodeProvider provider = new CSharpCodeProvider();

      CompilerResults results = provider.CompileAssemblyFromSource(options, _class.ToString());

      if (!results.Errors.HasErrors)

      {

        //Invoke the Expression Method

        Type t = results.CompiledAssembly.GetType(string.Format("{0}.{1}", namespaceName, className));

        object instance = t.InvokeMember(t.Name, 

          BindingFlags.CreateInstance | 

          BindingFlags.Instance | 

          BindingFlags.NonPublic | 

          BindingFlags.Public, null, null, null, CultureInfo.CurrentCulture);

        if (instance != null)

        {

          string result = (string)t.InvokeMember(methodName, 

            BindingFlags.InvokeMethod | 

            BindingFlags.Instance | 

            BindingFlags.Public | 

            BindingFlags.NonPublic, null, instance, null, CultureInfo.CurrentCulture);

          Console.WriteLine("{0}{1}", result, expression);

        }

      }

      Console.ReadLine();

    }

  }

}

Comments

[software developers]

Hey, that was interesting,

Thanks for sharing,

Keep up the good work