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Debugging

K. R. C. Wijesinghe

TrainerVirtusa Corporation

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Debugging using Visual Studio .Net IDE

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Types of Errors

• Compile Time Errors (Syntax Errors)E.g. for (int i = 0; i < V.Length; i++] {

V [ i ] = 0; }

• Run-time Errors (Exceptions)E.g. for (int i = 0; i <= V.Length; i++) {

V [ i ] = 0; }

• Logical ErrorsE.g. for (int i = 1; i < V.Length; i++) {

V [ i ] = 0; }

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Debug and Trace classes

• These classes are defined in System.Diagnosis namespace.

• Both classes has the same methods and properties.

• Methods in Debug class will work only if “DEBUG” macro is defined. (This is defined in Debug builds by default).

• Methods in Trace class will work only if “TRACE” macro is defined. (This is defined in Visual Studio.NET projects by default).

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ASSERTS

• Asserts are used to ensure that a given condition is true at a given point in the program.

• Asserts will stop the program execution temporarily, if the condition is false, and provide you with three options. They are “Abort”, ”Retry” and “Ignore”.• Abort – Stop the program execution.• Retry – Take you to the Debug mode.• Ignore – Continue with the program.

E.g.

Stop execution if Obj is nullTrace.Assert (Obj != null);

Stop execution and display the message “Out of Range” if n > 100.Trace.Assert (n > 100, “Out of Range”);

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Logging

• Dumping information about intermediate steps of the program to an output device, without stopping the execution.

• This is very important in locating errors in complex programs.

• The default output is going to the “Output” window of Visual Studio.NET IDE.

• It can be send to console, a file or Windows event log.

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Logging Example

Trace.WriteLine (“Begin Section 1”);int n = 100;Trace.Indent( );Trace.WriteLine(“Inside Section 1”);Trace.WriteLine( n );n += 100;Trace.WriteLineIf (n > 150, “n greater than 150”);Trace.Unindent( );Trace.WriteLine(“End Section 1”);

Output:

Begin Section1Inside Section 1100 n greater than 150

End Section 1

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Sending output to Other devices

// Output to Console Trace. Listeners.Add (new TextStreamTraceListener(Console.Out);

// Output to a file TextWriterTraceListener TraceFile = new TextWriterTraceListener(@“C:\Temp\

Test.log”); Trace.Listeners.Add (TraceFile ); ... TraceFile.Close();

// Output to event log EventLogTraceListener ELog = new EventLogTraceListener("TestLog1"); Trace.Listeners.Add (ELog);

Trace.WriteLine( “Test Log Message”);