text: (or which namespace do I need
  for type <type-name>?)
  When compiling a VB.Net application the compiler generates the following
  error:
  error BC30002: Type 'TTTT' is not defined.'
  Earlier versions of visual studio may not include the error code
  ("error BC30002:").
  error BC30002:
  where 'TTTT' is the name of a class.
  TTTT
  If you are using C# then the error is slightly different:
  error CS0246: The type or namespace name 'TTTT' could not be found
  (are you missing a using directive or an assembly reference?)
  in this case please refer to the C# version of this article "The
  type or namespace name could not be found".
  The compiler does not recognise the class name 'TTTT'.
  This is either because the class name is miss-spelt or because the compiler
  could not find a corresponding definition.
  For example:
  dim connection as OdbcConection
  Here the class name should have been 'OdbcConnection',
  so the solution is to correct the spelling.
  OdbcConnection
  dim connection as OdbcConnection
  .
  .
  [Error] Type 'OdbcConnection' is not defined.
  In this example 'OdbcConnection' is defined in the namespace 'System.Data.Odbc'
  (although this differs been the .Net framework 1.0 and later versions).
  Try importing the necessary namespace, so in this case:
  Imports System.Data.Odbc
  Note that this "Imports" statement must be included
  at the very top of the file (i.e. before any code).
  The following table (which is not exhaustive)
  lists .NET class names together with the namespace that defines them:
  I expect to add to this table over time.
  These notes are believed to be correct for VB.Net and
  C# for
  .NET 1.1, .NET 2, .NET 3.5 and .NET 4, and may apply to other versions as well.
  For the corresponding C# version of this article
  please see "The
  type or namespace name could not be found".
  About the author: Brian Cryer
  is a dedicated software developer and webmaster. For his day job he
  develops websites and desktop applications as well as providing
  IT services. He moonlights as a technical author and consultant.