It seems that I have encountered a scenario where many aspects of C# 2.0+ come into play.  I needed to handle conversion from an IDataReader.GetValue() result to a generic type, including Nullable<>.  It took me a while to figure it out and with a little help from this snippet, I was quite please with the result.  So, I decided to share.

   1: private static T NullValue<T>( object testValue, T nullValue )

   2: {

   3:     T returnValue;

   4:     if( testValue is DBNull )

   5:     {

   6:         returnValue = nullValue;

   7:     }

   8:     else if( typeof(T).GetGenericTypeDefinition().Equals( typeof(Nullable<>) ) )

   9:     {

  10:         returnValue = (T)Convert.ChangeType( testValue, Nullable.GetUnderlyingType( typeof(T) ) );

  11:     }

  12:     else

  13:     {

  14:         returnValue = (T)Convert.ChangeType( testValue, typeof(T) );

  15:     }

  16:     return returnValue;

  17: }

It turns out that System.Decimal cannot be converted directly to Nullable<Int32>.  However, it can be converted to Int32, which can be converted to Nullable<Int32>.  I guess the transitive property doesn't apply to type conversion.