Invalid Column Error

Question

 I am a beginner of ADO.net. When i try to retrieve a column data by giving a condition an exception is raised saying that the AccountNo is invalid.Could u please help me out. My table name is Bank_Account1 with three columns 
AccountNo-int type with IsIncrement-true
Name-varchar(20)
Age-int
Balance-float
The code is Uploaded in a zip file

Thank You