Turn on CLS compliance checking in Visual Studio 2010

• 1 Open file called AssemblyInfo.cs under the Properties node for the project in Solution Explorer
  
• 2 To make the assembly CLS-compliant and to have the compiler check this claim,
  add the following line somewhere in the file (at the bottom will do)
  
• 3 [assembly: CLSCompliant(true)]
  
• N You must be using System namespace