Object name error
This error was caught by several other readers, but you are right. The table on page 43 call the output textbox object txtResult, but the narrative on the subsequent pages refer to txtDisplayOutput. I started the code using txtResult, but then switched to txtDisplayOutput since it's a bit more descriptive. However, I forgot to change it in the table. Use txtDisplayOutput and I think you'll find everything works okay.
Jack Purdum, Ph.D.
Author: Beginning C# 3.0: Introduction to Object Oriented Programming (and 14 other programming texts)