Returns an indication whether the specified object is of type DBNull.
true if value is of type DBNull; otherwise, false.
The Convert.IsDBNull(object) method tests whether the value parameter is equal to DBNull.Value. It is equivalent to the following code:
code reference: System.Convert.IsDBNull#1
DBNull.Value is used to indicate a value that is missing. It is not equivalent to null or to string.Empty. Therefore, code such as Convert.IsDBNull(null) in C# or Convert.IsDBNull(Nothing) in Visual Basic returns false.