public class HandleConcurrencyExceptionAttribute : FilterAttribute, IExceptionFilter
    {
        private PropertyMatchingMode _propertyMatchingMode;
        /// <summary>
        /// This defines when the concurrencyexception happens, 
        /// </summary>
        public enum PropertyMatchingMode
        {
            /// <summary>
            /// Uses only the field names in the model to check against the entity. This option is best when you are using 
            /// View Models with limited fields as opposed to an entity that has many fields. The ViewModel (or model) field names will
            /// be used to check current posted values vs. db values on the entity itself.
            /// </summary>
            UseViewModelNamesToCheckEntity = 0,
            /// <summary>
            /// Use any non-matching value fields on the entity (except timestamp fields) to add errors to the ModelState.
            /// </summary>
            UseEntityFieldsOnly = 1,
            /// <summary>
            /// Tells the filter to not attempt to add field differences to the model state.
            /// This means the end user will not see the specifics of which fields caused issues
            /// </summary>
            DontDisplayFieldClashes = 2
        }


        public HandleConcurrencyExceptionAttribute()
        {
            _propertyMatchingMode = PropertyMatchingMode.UseViewModelNamesToCheckEntity;
        }

        public HandleConcurrencyExceptionAttribute(PropertyMatchingMode propertyMatchingMode)
        {
            _propertyMatchingMode = propertyMatchingMode;
        }


        /// <summary>
        /// The main method, called by the mvc runtime when an exception has occured.
        /// This must be added as a global filter, or as an attribute on a class or action method.
        /// </summary>
        /// <param name="filterContext"></param>
        public void OnException(ExceptionContext filterContext)
        {
            if (!filterContext.ExceptionHandled && filterContext.Exception is DbUpdateConcurrencyException)
            {
                //Get original and current entity values
                DbUpdateConcurrencyException ex = (DbUpdateConcurrencyException)filterContext.Exception;
                var entry = ex.Entries.Single();
                //problems with ef4.1/4.2 here because of context/model in different projects.
                //var databaseValues = entry.CurrentValues.Clone().ToObject();
                //var clientValues = entry.Entity;
                //So - if using EF 4.1/4.2 you may use this workaround
                var clientValues = entry.CurrentValues.Clone().ToObject();
                entry.Reload();
                var databaseValues = entry.CurrentValues.ToObject();

                List<string> propertyNames;

                filterContext.Controller.ViewData.ModelState.AddModelError(string.Empty, "The record you attempted to edit "
                        + "was modified by another user after you got the original value. The "
                        + "edit operation was canceled and the current values in the database "
                        + "have been displayed. If you still want to edit this record, click "
                        + "the Save button again to cause your changes to be the current saved values.");
                PropertyInfo[] entityFromDbProperties = databaseValues.GetType().GetProperties(BindingFlags.FlattenHierarchy | BindingFlags.Public | BindingFlags.Instance);

                if (_propertyMatchingMode == PropertyMatchingMode.UseViewModelNamesToCheckEntity)
                {
                    //We dont have access to the model here on an exception. Get the field names from modelstate:
                    propertyNames = filterContext.Controller.ViewData.ModelState.Keys.ToList();
                }
                else if (_propertyMatchingMode == PropertyMatchingMode.UseEntityFieldsOnly)
                {
                    propertyNames = databaseValues.GetType().GetProperties(BindingFlags.Public).Select(o => o.Name).ToList();
                }
                else
                {
                    filterContext.ExceptionHandled = true;
                    UpdateTimestampField(filterContext, entityFromDbProperties, databaseValues);
                    filterContext.Result = new ViewResult() { ViewData = filterContext.Controller.ViewData };
                    return;
                }



                UpdateTimestampField(filterContext, entityFromDbProperties, databaseValues);

                //Get all public properties of the entity that have names matching those in our modelstate.
                foreach (var propertyInfo in entityFromDbProperties)
                {

                    //If this value is not in the ModelState values, don't compare it as we don't want
                    //to attempt to emit model errors for fields that don't exist.

                    //Compare db value to the current value from the entity we posted.

                    if (propertyNames.Contains(propertyInfo.Name))
                    {
                        if (propertyInfo.GetValue(databaseValues, null) != propertyInfo.GetValue(clientValues, null))
                        {
                            var currentValue = propertyInfo.GetValue(databaseValues, null);
                            if (currentValue == null || string.IsNullOrEmpty(currentValue.ToString()))
                            {
                                currentValue = "Empty";
                            }

                            filterContext.Controller.ViewData.ModelState.AddModelError(propertyInfo.Name, "Current value: "
                                 + currentValue);
                        }
                    }

                    //TODO: hmm.... how can we only check values applicable to the model/modelstate rather than the entity we saved?
                    //The problem here is we may only have a few fields used in the viewmodel, but many in the entity
                    //so we could have a problem here with that.
                    //object o = propertyInfo.GetValue(myObject, null);
                }

                filterContext.ExceptionHandled = true;

                filterContext.Result = new ViewResult() { ViewData = filterContext.Controller.ViewData };
            }
        }

           string source =
           @"
               namespace Foo
               {
                    public class Bar
                    {
                        static void Main(string[] args)
                        {
                            Bar.SayHello();
                        }

                        public static void SayHello()
                        {
                            System.Console.WriteLine(""Hello World"");
                        }
                    }
               }
            ";

using System;
using System.Collections.Generic;
//دو فضای نامی که برای این منظور اضافه شده‌اند
using Microsoft.CSharp;
using System.CodeDom.Compiler;

namespace compilerTest
{
   class Program
   {
       static void compileIt1()
       {
           //سورس کد ما جهت کامپایل
           string source =
           @"
               namespace Foo
               {
                    public class Bar
                    {
                        static void Main(string[] args)
                        {
                            Bar.SayHello();
                        }

                        public static void SayHello()
                        {
                            System.Console.WriteLine(""Hello World"");
                        }
                    }
               }
            ";

           //تعیین نگارش کامپایلر مورد استفاده
           Dictionary<string, string> providerOptions = new Dictionary<string, string>
                {
                    {"CompilerVersion", "v3.5"}
                };
           //تعیین اینکه کد ما سی شارپ است
           CSharpCodeProvider provider = new CSharpCodeProvider(providerOptions);

           //تعیین اینکه خروجی یک فایل اجرایی است بعلاوه مشخص سازی محل ذخیره سازی فایل نهایی
           CompilerParameters compilerParams = new CompilerParameters
           {
               OutputAssembly = "D:\\Foo.EXE",
               GenerateExecutable = true
           };

           //عملیات کامپایل در اینجا صورت می‌گیرد
           CompilerResults results = provider.CompileAssemblyFromSource(compilerParams, source);

           //اگر خطایی وجود داشته باشد نمایش داده خواهد شد
           Console.WriteLine("Number of Errors: {0}", results.Errors.Count);
           foreach (CompilerError err in results.Errors)
           {
               Console.WriteLine("ERROR {0}", err.ErrorText);
           }
       }

       static void Main(string[] args)
       {
           compileIt1();

           Console.WriteLine("Press a key...");
           Console.ReadKey();
       }
   }
}

using System;
using System.Collections.Generic;
using Microsoft.CSharp;
using System.CodeDom.Compiler;
using System.Reflection;

namespace compilerTest
{
   class Program
   {
       static void compileIt2()
       {
           //سورس کد ما جهت کامپایل
           string source =
           @"
               namespace Foo
               {
                    public class Bar
                    {
                        static void Main(string[] args)
                        {
                            Bar.SayHello();
                        }

                        public static void SayHello()
                        {
                            System.Console.WriteLine(""Hello World"");
                        }
                    }
               }
            ";

           //تعیین نگارش کامپایلر مورد استفاده
           Dictionary<string, string> providerOptions = new Dictionary<string, string>
                {
                    {"CompilerVersion", "v3.5"}
                };
           //تعیین اینکه کد ما سی شارپ است
           CSharpCodeProvider provider = new CSharpCodeProvider(providerOptions);

           //نحوه تعیین مشخص سازی کامپایل در حافظه
           CompilerParameters compilerParams = new CompilerParameters
           {
               GenerateInMemory = true,
               GenerateExecutable = false
           };

           //عملیات کامپایل در اینجا صورت می‌گیرد
           CompilerResults results = provider.CompileAssemblyFromSource(compilerParams, source);

           // اگر خطایی در کامپایل وجود نداشت متد دلخواه را فراخوانی می‌کنیم
           if (results.Errors.Count == 0)
           {
               //استفاده از ریفلکشن برای دسترسی به متد و فراخوانی آن
               Type type = results.CompiledAssembly.GetType("Foo.Bar");
               MethodInfo method = type.GetMethod("SayHello");
               method.Invoke(null, null);
           }
       }


       static void Main(string[] args)
       {
           compileIt2();

           Console.WriteLine("Press a key...");
           Console.ReadKey();
       }
   }
}

           string source =
           @"
             namespace Foo
             {
            
                 public class Bar
                 {
                     static void Main(string[] args)
                     {
                         Bar.SayHello();
                     }
            
                     public static void SayHello()
                     {
                         System.Console.WriteLine(""Hello World"");
                         var r = new System.Drawing.Rectangle(0,0,100,100);
                         System.Console.WriteLine(r);             
                     }
                 }
             }
            ";

Number of Errors: 1
ERROR The type or namespace name 'Drawing' does not exist in the namespace 'System' (are you missing an assembly reference?)

compilerParams.ReferencedAssemblies.Add("System.Drawing.Dll");

await(.+);

await $1.ConfigureAwait(false);