>>>>>I'd say it means that tdNullable can be null http://msdn.microsoft.com/en-us/library/b3h38hb0.aspx#Y1537
>>>>>
>>>>>You may want to test tdNullable.HasValue to verify whether it contains a value
>>>>
>>>>Is there a way to avoid this question mark if there is a possiblity to receive a null value for the parameter?
>>>
>>>
>>>try
>>>

>>>Private Function GetNonNullable(ByVal tdNullable As Nullable(Of Date)) As Date
>>>

>>
>>Hence the ? is easier!
>
>
>I know that - but if one wants to avoid the ?

You can't. DateTime cannot contain null. DateTime? can. In your method, however, you'll want to check it:

   void MyMethod(datetime? value)
   {
     if(value.HasValue())
     {
         DoSomethingElse(value.Value); //passes in the value as DateTime type
     }
     ...
   }