Opc data Access Automation Specification

Watching for Errors

 

An error trap is enabled when Visual Basic executes the On Error statement, which specifies an error handler. 

The error trap remains enabled while the procedure containing it is active — that is, until an Exit Sub, Exit 

Function, Exit Property, End Sub, End Function, or End Property statement is executed for that procedure.  

To set an error trap that jumps to an error-handling routine, use a On Error GoTo 

line

 statement, where 

line

 

indicates the label identifying the error-handling code. 

 

Handling the Errors

 

The first step in writing an error-handling routine is adding a line label to mark the beginning of the error 

handling routine. The line label should have a descriptive name and must be followed by a colon.  

The body of the error handling routine contains the code that actually handles the error, usually in the form of 

a Case or If…Then…Else statement. You need to determine which errors are likely to occur and provide a 

course of action for each. 

The Number property of the Err object contains a numeric code representing the most recent run-time error.  

The error number from the Number property on the Err object contains the value that you would call 

GetErrorString with to covert the error number into a readable string.