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Application Developer
Early and late binding

by Mark Horninger

This month’s software application development question is on VB and is written by Mark Horninger. When interviewing developers you need to make sure they understand how to apply the most effective coding principles for the job. Here is a question for your to use that mid-level developers with at least 2 years experience with Visual Basic should get correct.


What is the difference between early and late binding and which is better? Why?


What to look for in your candidate's response:

Early binding is generally better since it is faster based on the type info that is compiled into the application at compile time. Late binding requires extra calls to determine object information at run time that makes it slower. Early binding affects the speed at which an object's methods can be accessed using the object variable. A compiler will provide error checking of the object variables if they are early bound versus late bound. However, it may be desirable to declare an object variable without a type library (example: Dim oX as object) if the developer needs to be able to pass any kind of object as an argument to a procedure. When an object variable is declared "as object" it is not strongly typed and it's binding will be late.

When interviewing candidates, probe their understanding of why early binding is better, rather than accepting the answer 'it's better'.


Early binding examples:

Dim oX as excel.Spreadsheet
or
Dim oX as New excel.Spreadsheet

Late Binding Example

Dim oX as object
set oX = createobject("excel.Spreadsheet")


About the author

Mark Horninger, A+, MCSE+I, MCSD, MCDBA
is President and founder of Haverford Consultants Inc., located in the suburbs of Philadelphia, PA. He develops custom applications and system engineering solutions, specializing primarily in Microsoft operating systems and Microsoft BackOffice products. He has over 10 years of computer consulting experience and has passed 24 Microsoft Certified Exams. During his career Mark has worked on many extensive and diverse projects including database development, application development, training, embedded systems development and Windows NT and 2000 project rollout planning and implementations. Mark lives with his wife Debbie and two children in Havertown, Pa.

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