Most .NET 4 shared hosting providers offering their customers a medium trust environment. This is not a problem for most web applications unless the applications uses MySQL in combination with the .NET MySQL driver (MySQL.Data.dll). The MySQL driver connects to the MySQL database using a socket. However, sockets are not allowed in medium trust. The application will throw a SecurityException with the following message:
Request for the permission of type 'System.Net.SocketPermission, System, Version=184.108.40.206, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed.
In order to fix this there are three solutions:
1. Instead of MySQL, use Microsoft SQL server.
2. Move to a hosting provider that supports a full trust environment or get your own server.
3. Ask your hosting provider to update the medium trust policy with SocketPermission. The steps will be explained here:
Open the following file in a text editor:
Or when you are running 64 bit:
Inside the SecurityClasses tag, add the following line:
<SecurityClass Name="SocketPermission" Description="System.Net.SocketPermission, System, Version=220.127.116.11, Culture=neutral, PublicKeyToken=b77a5c561934e089"/>
Scroll down and look for the following PermissionSet:
<PermissionSet version="1" Name="ASP.Net">
Add the following inside this PermissionSet:
<IPermission class="SocketPermission" version="1" Unrestricted="true" />
That’s all, a restart of IIS is, as far as I know, not necessary.