Hello, in this post, I will describe short tutorial about how to solve The specified string is not in the form required for an e-mail address. I found many people find this error on forums. Here is the error message:

As you can see above, that is the error message that you might find. So, what’s the problem?

OK, the problem in this case is not from the page itself, but it comes from your web.config file. This configuration file has a <system.net /> element that enables you to store information about the mail server and the from account. I will give you 2 examples below how it will crash your page:

<system.net>
  <mailSettings>
    <smtp from="you.yourprovider.com">
      <network host="smtp.yourprovider.com"/>
    </smtp>
  </mailSettings>
</system.net>

Please see the missing @ symbol in the mail address. And other error may come from incorrect encoded angled brackets, see this:

<system.net>
  <mailSettings>
    <smtp from="Your Name &lt;[email protected]">
      <network host="smtp.yourprovider.com"/>
    </smtp>
  </mailSettings>
</system.net>

This from attributes has an opening < character (encoded as &lt;) but lacks the closing > bracket. To avoid the error, make sure the e-mail address in the from attribute has a valid syntax and uses the right angled brackets (if you use both a name and an e-mail address) like this:

<system.net>
  <mailSettings>
    <smtp from="Your Name &lt;[email protected]&gt;">
      <network host="smtp.yourprovider.com"/>
    </smtp>
  </mailSettings>
</system.net>

If you are curious why your code crashed, then you can use Reflector and take a look in the class’s constructor code:

public MailMessage()
{
  this.body = string.Empty;
  this.message = new Message();
  if (Logging.On)
  {
    Logging.Associate(Logging.Web, this, this.message);
  }
  string from = SmtpClient.MailConfiguration.Smtp.From;
  if ((from != null) && (from.Length > 0))
  {
    this.message.From = new MailAddress(from);
  }
}

Here you can see that the code uses the (internal and static) MailConfiguration property of the SmtpClient class that in turn provides access to the From name and address. This name and address value is then passed into the constructor of the MailAddress class which performs the actual validation using its private ParseValue method.

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With more and more people and companies developing websites by Microsoft .NET technology, ASP.NET 4.5 shared web hosting comes to be the major solution provided by many web hosting companies. Most of people choose an ASP.NET 4.5 web host considering about .NET framework version, ASP.NET MVC support, SQL Server database, disk space or bandwidth but they usually ignore the most important feature “IIS security level”. That determines whether the ASP.NET 4.5 websites can run successfully on the shared web host. In result to, if you developing an ASP.NET 4.5 website that works well in the local development environment and attempt to run it in the ASP.NET 4.5 shared web host, you may get the following exception,

System.Security.SecurityException: That assembly does not allow partially trusted caller

This is caused by the security level of the ASP.NET 4.5 shared web host that your application is forced to run with the limited permission, by locking down the access to server file system, preventing the background threads, or interacting with COM interfaces, etc.

ASP.NET 4.5 Web Hosting Trust Levels

This security level is known as the Trust Level of IIS for ASP.NET 4.5 websites. 

It can be configured with the following setting:

• Full Trust: website can do everything that the account of the application pool can do on the web server. This is the most flexible configuration for running websites on the shared web hosts. You won’t have any problems unless your website accesses the system information.
• High Trust: websites are limited to call unmanaged code, e.g. Win32 APIs, COM interop.
• Medium Trust: websites are limited to access the file system except the website application directory, system registry, Code DOM, and more (we will talk it later), compared to High Trust.
• Low Trust & Minimal Trust: these two options restrict the websites seriously. Even they don’t allow websites to call the service out of process, such as database, network, etc. But we never saw an ASP.NET 4.5 shared web host configured with either one of these two options.

Full Trust and Medium Trust are two widely used levels in ASP.NET 4.5 shared web hosting. The full trust provides best flexibility but it has potential security issues to the shared server, especially when the web hosting provider doesn't have rich experience on setting up Windows permission and IIS. Compared to Full Trust, you have to review the website carefully before you go with a web host only supports Medium Trust Level. You can refer to the following checkpoints for the review,

• The website shall not call unmanaged APIs.
• The website shall not access to file system, system registry, event logs and anything else related to the system.
• The website shall not generate code for execution dynamically using Code DOM.
• The website shall not use XslTransform to transform something from XML using XSLT.
• The website has to be signed with a Strong Name.

Check with the web page from Microsoft about which namespaces and classes are not supported in Medium Trust environment. 

And here is quick way to confirm the compatibility of websites to Medium Trust Level, in the local environment,

1. Add partially trusted callers attribute into AssemblyInfo.cs file of the website project, as following code snippet,

[assembly: AllowPartiallyTrustedCallers]

2. Add the following line into the web.config,

<trust level="Medium" />

Suggestion

It's a tradeoff between these two trust level. But if you confirm that the website can run successfully with Medium Trust in your local environment, we suggest you choose an ASP.NET 4.5 web host with Medium Trust only. It shall be more secure and reliable anyway. If you host the website based on 3rd party framework such as DotNetNuke, or using 3rd party component, we recommend you going with Full Trust web host.

This articles describe one of the newest runtime features in ASP.NET 4.5. I will describe about Muticore Just-In-Compiler (JIT) in the .NET framework 4.5.

Multicore Just-in-Time (JIT) 

In the .NET framework 4.5, Microsoft has introduced an enhancement of the pervious JIT compiler by making it a Multicore JIT compiler, that runs on the two cores and supports parallelism in the compilation process in order to improve the launch performance during application startup.

From the developer point of view the Multicore JIT is a very cool runtime feature in .NET Framework 4.5 to improve their productivity and speed up the overall performance of an application. Now the developer can benefit from multicore processors to speed up the application compilation process.

The Multicore JIT compiler works in parallel with two cores. Because of the two cores, Multicore JIT can make your application start the process faster at startup. Multicore JIT provides significant improvements to Web based applications as well as Desktop Windows Presentation Foundation (WPF) applications.

Working of Multicore JIT

Nowadays, every PC has at least two cores, so the JIT compiler is built to make the investment worthwhile. Using the Multicore JIT, methods are compiled on two CPUs so that the application is able to reach the end of its startup execution quickly.

The compilation process is done in two cores that run in parallel executing the Multicore JIT compiler. The more effective Multicore JIT will reduce the startup time of an .NET application. 

Multicore JIT uses the two modes of operation.

Recording mode: It is the first mode, when JIT compiles the entire program and creates a JIT profile using a profile optimization class and saves the profile that was executed to a given folder to disk.

Playback mode: This mode is used when the application is launched subsequently. Playback mode is used to load the profile that was saved during the Recording mode from the disk using the background JIT thread in order to support the main thread.

The feature works by the JIT compiling the methods likely to be executed based on profiles created during previous compilations, that will runs on a separate processor core taking care of the JIT Compilation while the main execution thread runs on a different core.

In the ideal case, the second core quickly gets ahead of the mainline execution of the application, so whenever a method is required it is already compiled. As a result, the main thread doesn't need to do as much compilation, and your application launches faster.

In order to know which methods to compile, the feature generates profile data in the Recording mode that keeps track of the methods that are executed. Then the next time the application runs the call will look for that profile and when it finds it then it plays back; that means it starts compiling all the methods that was saved for that profile.

Note: MultiCore JIT requires a multicore machine to take advantage of its algorithms otherwise the CLR will ignore it on single core machines.

How to enable Multicore JIT in an .NET 4.5 application.

You can use this feature of the runtime to significantly improve the startup times of both client applications and Web sites in .NET framework 4.5.

Since ASP.NET applications run in a hosted environment, this feature is turned on for these applications automatically. Therefore JIT compiling using multiple cores is enabled by default in ASP.NET 4.5 and Silverlight 5.

But, if you want to disable this feature in your ASP.NET 4.5 applications then write the following code in the web.config file.

<system.web>
  <compilation profileGuidedOptimizations="None" />
</system.web>

But in a Windows based application, you will need to enable Multicore JIT feature explicitly.

Let's see how.

It is simple to use Multicore JIT, there is a class in the .NET Framework named "System.Runtime.ProfileOptimization" that you can use to start profiling at the entry point of your application. 

Optimization Profilers

The ProfileOptimization is a new type introduced in .Net 4.5 to improve the startup performance of application domains in applications that require the just-in-time (JIT) compiler by performing background compilation of methods that are likely to be executed, based on profiles created during previous compilations.

See the MSDN documentation for more information.

http://msdn.microsoft.com/en-IN/library/system.runtime.profileoptimization.aspx

The two methods that you can call at the entry point of your application.

SetProfileRoot: This method is used to specify the root path, where to save the JIT profile compiled information for optimization.

StartProfile: This method is used to start Multcore just in-time compilation.

You must write the following code in your application constructor in order to enable Multicore JIT.

public App()
{

 ProfileOptimization.SetProfileRoot(@"C:\MyAppFolder");
 ProfileOptimization.StartProfile("Startup.Profile");

}

Now that's all to enable the Multicore feature in your application; the rest of the work will be handled by the CLR automatically.