Your SlideShare is downloading. ×
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Vb.net session 12
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Vb.net session 12

551

Published on

Published in: Technology
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
551
On Slideshare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
0
Comments
0
Likes
0
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. Exception Handling, Debugging and TestingWindows ApplicationsPre-assessment Questions 1. Which of the following is a valid specific culture: a. fr b. de c. fr-France d. fr-Fr 2. Which of the following involves writing code in such a way that it is culture and language neutral? a. Globalization b. Localization c. Culture-specific formatting d. Deployment ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 1 of 50
  • 2. Exception Handling, Debugging and TestingWindows ApplicationsPre-assessment Questions (Contd.) 1. Which method is used to create an instance of the Encoding class? a. Encoding.GetEncoding b. Encoding.newEncoding c. new d. Encoding.generateEncoding 2. Which of the following properties must be set for conveying information about a control to the accessibility aids? a. Name b. AccessibleName c. AccessibleIdentity d. AidName ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 2 of 50
  • 3. Exception Handling, Debugging and TestingWindows ApplicationsPre-assessment Questions (Contd.) 1. Which of the following is not a culture-specific class? a. DateTimeFormatInfo b. Calendar c. NumberFormatInfo d. LanguageInfo ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 3 of 50
  • 4. Exception Handling, Debugging and TestingWindows ApplicationsSolutions to Pre-assessmentQuestions 1. d. fr-Fr 2. a. Globalization 3. a. Encoding.GetEncoding 4. b. AccessibleName 5. d. LanguageInfo ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 4 of 50
  • 5. Exception Handling, Debugging and TestingWindows ApplicationsObjectives In this lesson, you will learn to: • Handle and raise exceptions • Develop test plans • Configure the debugging environment • Use the Break mode to debug an application • Use debugger windows to trace and debug an application • Implement custom trace listeners • Implement trace switches ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 5 of 50
  • 6. Exception Handling, Debugging and TestingWindows ApplicationsException Handling • An exception is termed as an abnormal condition encountered by an application during execution. • Exception handling is the process of providing an alternate path of execution when the application is unable to execute in the desired way. • By handling exceptions, you can prevent an application from terminating abruptly when an error is encountered. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 6 of 50
  • 7. Exception Handling, Debugging and TestingWindows ApplicationsOverview of Exception Handling • Exceptions may be handled by placing specific code in an application that gets executed when an exception is raised. • The exception handling code prevents the program from terminating abruptly and allows you to take appropriate action. • Exception handling may be used in any method that uses operators that may generate an exception, or that calls into or accesses other procedures that may generate an exception. • If an exception occurs in a method that does not contain an exception handler, then the exception is propagated back to the calling method. • If the calling method also has no exception handler, then the exception is propagated back to that called method. • When an error occurs, an object is created automatically that stores information about the error. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 7 of 50
  • 8. Exception Handling, Debugging and TestingWindows ApplicationsTypes of Errors • There are three types of errors that can occur in an application: • Syntax Errors: A syntax error occurs when the compiler cannot compile the code. • Run-time Errors: A run-time error occurs when an application attempts to perform an operation that is not allowed. • Logical Errors: A logical error occurs when an application compiles and runs properly but does not produce the expected results. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 8 of 50
  • 9. Exception Handling, Debugging and TestingWindows ApplicationsTypes of Exception Handling • Visual Basic .NET provides these two ways to handle exceptions: • Structured Exception Handling • Unstructured Exception Handling ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 9 of 50
  • 10. Exception Handling, Debugging and TestingWindows ApplicationsStructured Exception Handling • All the exceptions are derived from the System.Exception class. • The hierarchy of the exception classes is displayed in the given figure. System.Exception System.ApplicationException System.Windows.Forms.AxHost.InvalidActiveXStateException System.Runtime.Remoting.MetadataServices.SUDSParserException System.IO.IsolatedStorage.IsolatedStorageException System.Runtime.Remoting.MetadataServices.SUDSGeneratorException System.SystemException ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 10 of 50
  • 11. Exception Handling, Debugging and TestingWindows ApplicationsStructured ExceptionHandling(Contd.) • The exception classes derived from the System.Exception class are discussed below: • System.ApplicationException— This exception is thrown by user created applications. • System.Windows.Forms.AxHost.InvalidActiveXStateException— This exception is thrown when the ActiveX control that is in an invalid state is called by an application. • System.Runtime.Remoting.MetadataServices.SUDSParserException— This exception is thrown when the parsing process of Web Services Description Language (WSDL) generates an error. • System.IO.IsolatedStorage.IsolatedStorageException— This exception is thrown when an error is generated in an isolated storage operation. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 11 of 50
  • 12. Exception Handling, Debugging and TestingWindows ApplicationsStructured ExceptionHandling(Contd.) • System.SystemException — This exception class acts as a base class for all the predefined system exceptions. Some of the classes derived from this class are given below: • System.IO.IOException • System.Data.DataException • Sytsem.Data.SqlClient.SqlException • System.IndexOutOfRangeException • System.NullReferenceException • In structured exception handling, the application is divided into blocks of code. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 12 of 50
  • 13. Exception Handling, Debugging and TestingWindows ApplicationsStructured ExceptionHandling(Contd.) • The structure of the Try…Catch…Finally statement is given below: Try This block includes the code that can raise an error. Catch (optional filters) This block includes the code that runs if the code in The Try block gives an error and the filter on the Catch statement is true, if specified. (Additional Catch blocks) Finally This block includes the code that will always run just before the Try statement exits. End Try ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 13 of 50
  • 14. Exception Handling, Debugging and TestingWindows ApplicationsUnstructured Exception Handling • In unstructured exception handling, an On Error statement is placed in a code block. • The On Error statement handles any error that occurs in that code block. • When an error occurs in a called procedure that does not have an On Error statement, the exception is passed back to the calling procedure and the error is handled by the calling procedure. • The Exit Sub statement should be placed immediately before the error handler block. • You can use the On Error Resume Next statement to specify that when an error occurs, the control should pass to the next line of code following the line in which the error occurred. • You can use the On Error GoTo 0 statement in a procedure to disable any error handler. • Unstructured exception handling is not recommended because it is difficult to maintain the code containing the On Error statement. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 14 of 50
  • 15. Exception Handling, Debugging and TestingWindows ApplicationsThe Error Object • When an error occurs in an application, an instance of the Error object is created and the information about the error, such as the error message and number, is stored in it. • The properties of the Error object that are commonly used are: • Number — Contains the integer value of the error. • Description — Contains the error text. • Source — Contains the information about the object that generated the error. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 15 of 50
  • 16. Exception Handling, Debugging and TestingWindows ApplicationsUser-defined Exceptions • In addition to handling pre-defined exceptions, users can create their own exceptions. • User-defined exception classes are derived from the ApplicationException class. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 16 of 50
  • 17. Exception Handling, Debugging and TestingWindows ApplicationsRaising Exceptions • There are instances when you want to raise exceptions. • Exceptions can be explicitly thrown in an application by using the Throw() method. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 17 of 50
  • 18. Exception Handling, Debugging and TestingWindows ApplicationsDebugging a Windows-basedApplication • When writing code for applications, errors may be introduced in programs, these errors are called bugs. • The process of locating and fixing bugs in a program is called Debugging. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 18 of 50
  • 19. Exception Handling, Debugging and TestingWindows ApplicationsOverview of Debugging • Visual Basic .NET provides a set of tools that allow you to trace and correct errors in your programs in the development environment itself. • To assist you in debugging logical and run-time errors, Visual Basic.NET provides extensive debugging tools. • Another method to access the debugging tools is from the Debug menu. • By using the debugging tools, you can perform the following actions: • Start execution • Break execution • Step through execution • Stop execution ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 19 of 50
  • 20. Exception Handling, Debugging and TestingWindows ApplicationsConfiguring the DebuggingEnvironment • The Debug version is built for debugging and the Release version is built for the final release distribution. • The Debug configuration of a program is compiled with full symbolic debug information and no optimization. • Optimization complicates debugging as the relationship between the source code and the generated instructions is more complex. • The Release configuration of a program is fully optimized and contains no symbolic debug information. • You can switch between Release and Debug versions by choosing Debug (or Release) from the Solution Configurations list box on the Standard toolbar. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 20 of 50
  • 21. Exception Handling, Debugging and TestingWindows ApplicationsUsing the Break Mode • When debugging, an application can be in the run mode or in the break mode. • In Visual Basic.NET, you can debug a code in the break mode. • In this mode, Visual Basic provides the ability to execute the application step-by-step. • The values of the variables and expressions can be evaluated in this mode. • When an application is running, in order to switch to the break mode, you can execute any of the following actions at run time: • Press the Ctrl and Break keys together • Select the Break option from the Run menu • Click the Break button on the Debug toolbar ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 21 of 50
  • 22. Exception Handling, Debugging and TestingWindows ApplicationsSetting a Breakpoint • A break point can be set on an executable line of code. • To set a breakpoint, you need to identify the statement where the error starts. • You can remove a breakpoint from a code by selecting Remove Breakpoint from the shortcut menu of the code line at which the breakpoint is set. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 22 of 50
  • 23. Exception Handling, Debugging and TestingWindows ApplicationsStepping Through an Application • When you set a breakpoint in an application and start the application using the Start option, the application execution halts at the breakpoint and the execution enters the break mode. • In the break mode, you can select any of the following Debug menu options for executing the code: • Step Into • Step Over • Step Out ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 23 of 50
  • 24. Exception Handling, Debugging and TestingWindows ApplicationsThe Debugger Windows • When an application runs or is in the break mode, you can use the following windows to trace and debug an application: • Call Stack window • Watch window • Output window • Locals window • Immediate window ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 24 of 50
  • 25. Exception Handling, Debugging and TestingWindows ApplicationsCall Stack Window • When an application is in the break mode, you can find the sequence of the called procedures by using the Call Stack window. • The Call Stack window displays the procedure names, the parameter types, and the parameter values. • You can display the Call Stack window by selecting Windows from the Debug menu and then selecting the Call Stack option from the Windows submenu. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 25 of 50
  • 26. Exception Handling, Debugging and TestingWindows ApplicationsWatch Window • Using the Watch window, you can change the values of variables or expressions in the break mode and observe how these different values affect your code. • Each variable or expression that you observe in the Watch window is called a watch expression. • Visual Basic. NET automatically monitors watch expressions. • The Watch window can be displayed by selecting Windows from the Debug menu and then selecting Watch1 from the Watch submenu. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 26 of 50
  • 27. Exception Handling, Debugging and TestingWindows ApplicationsOutput Window • The Output window is useful in displaying debug messages, such as build errors and any user-defined messages during run time. • The Output window is displayed by using the ViewOther WindowsOutput option. • You can display debug messages during run time by using the methods of the Debug class. • The Debug class is derived from System.Diagnostics namespace and contains methods that you can use to debug applications. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 27 of 50
  • 28. Exception Handling, Debugging and TestingWindows ApplicationsLocals Window • The Locals window is a debugging tool that allows you to view the values present in the variables declared in the local procedures. • To display the Locals window, select DebugWindowsLocals option when debugging in the break mode. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 28 of 50
  • 29. Exception Handling, Debugging and TestingWindows ApplicationsImmediate Window • The Immediate window is a debugging tool to check the values present in the global and local variables. • The Immediate window allows you to: • Set the value of a variable to observe the change in the result based on the value that is set. • Create or destroy objects. • To start the Immediate window select DebugWindowsImmediate to open the Immediate window. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 29 of 50
  • 30. Exception Handling, Debugging and TestingWindows Applications Demo Using Breakpoints ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 30 of 50
  • 31. Exception Handling, Debugging and TestingWindows ApplicationsProblem Statement • An application has been created to display the product ID for a product that costs more than $3000. • A Windows Form has been designed with a ListBox control named lbprodid. • A data adapter named OleDbDAProduct has been created, and the Base_Cost and ProdID columns of the table Product have been retrieved. • A dataset named DsProduct1 has been generated for the data adapter. • The following code has been written for the Load event of the form to display the ProductID of the products with cost more than $3000 in the list box. Dim criteria As String Dim sort As String Dim dt As DataTable Dim result() As DataRow Dim ctr As Integer OleDbDAProduct.Fill(DsProduct1) dt = DsProduct1.Tables("Product") criteria = "Base_Cost > 3000" ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 31 of 50
  • 32. Exception Handling, Debugging and TestingWindows ApplicationsProblem Statement (Contd.) sort = "ProdID DESC" result = DsProduct1.Product.Select(criteria, sort) For ctr = 0 To (result.Length - 1) lbprodid.Items.Add(result(0)("ProdID").ToString) Next ctr • However, the application does not give the expected output. The list box displays one product ID multiple times. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 32 of 50
  • 33. Exception Handling, Debugging and TestingWindows ApplicationsSolution • To locate the error in the above program, the following steps need to be performed: 1. Identify the starting point to search for errors. 2. Set a breakpoint. 3. Run the application and trace the error. 4. Rectify the code. 5. Verify the output of the code. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 33 of 50
  • 34. Exception Handling, Debugging and TestingWindows Applications Demo Debugging a Windows-based Application ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 34 of 50
  • 35. Exception Handling, Debugging and TestingWindows ApplicationsProblem Statement • An application has been developed that displays the corresponding base cost and the product name of the product ID selected by the user from a list box. • A data adapter named OleDbDAProduct has been created, and the Base_Cost and ProdID columns of the table Product have been retrieved. • A dataset named DSProduct has been generated for the data adapter. • A ListBox control named lbprodid, two TextBox controls, and a Button control with Text property set to Display have been added to the Form. The following general level declarations have been made. A ListBox control named lbprodid, two TextBox controls, and a Button control with Text property set to Display have been added to the Form. The following general level declarations have been made. Dim dt As DataTable Dim result(), resultarray As DataRow Dim prodid, criteria, sort As String Dim ctr As Integer ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 35 of 50
  • 36. Exception Handling, Debugging and TestingWindows ApplicationsProblem Statement (Contd.) • The following code has been added: Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load OleDbDAProduct.Fill(DSProduct) dt = DSProduct.Tables("Product") criteria = "Base_Cost > 3000" sort = "ProdID DESC" result = DSProduct.Product.Select(criteria, sort) For ctr = 0 To (result.Length - 1) lbprodid.Items.Add(result(ctr)("ProdID").ToString) Next ctr End Sub ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 36 of 50
  • 37. Exception Handling, Debugging and TestingWindows ApplicationsProblem Statement (Contd.) Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Display.Click prodid = lbprodid.SelectedItem prodid = "P014" dt = DSProduct.Tables("Product") resultarray = dt.Rows.Find(prodid) TextBox1.Text = resultarray(1) TextBox2.Text = resultarray(2) End Sub • However, the application displays the product name and the base cost of the product ID P014 regardless of the ID selected by the user. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 37 of 50
  • 38. Exception Handling, Debugging and TestingWindows ApplicationsSolution • To solve the preceding problem, the following steps need to be performed: 1. Identify the mechanism to debug the code. 2. Implement debugging. 3. Rectify the code. 4. Verify the output of the code. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 38 of 50
  • 39. Exception Handling, Debugging and TestingWindows ApplicationsTesting a Windows-based Application • Testing an application ensures that it fulfills the requirements for which it was designed and meets quality expectations. • An application must be tested to ensure that it meets customer expectations. • The compiler can detects only syntax errors, but the run-time errors and logical errors might not be exposed unless the application is thoroughly tested. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 39 of 50
  • 40. Exception Handling, Debugging and TestingWindows ApplicationsOverview of Testing • Testing measures the quality of the software you are developing. • Testing is undertaken to find and resolve the defects in your application. • Testing can be of various types, which include: • Unit testing: Unit testing consists of isolating the smallest piece of testable software from the remaining application and determining whether it behaves as expected. • Integration testing: Integration testing combines two or more tested units into a component and tests the interface between them. • Regression testing: In regression testing you rerun the existing tests against the modified code to determine whether the changes have affected anything that was working correctly before the modification of code. • Acceptance testing: During acceptance testing, users are allowed to use the application and give feedback about the functionality, effectiveness, and efficiency of the application as per the requirements. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 40 of 50
  • 41. Exception Handling, Debugging and TestingWindows ApplicationsDeveloping a Test Plan • Planning for a test includes budget, schedule, and performance considerations. • Preparing a proper test plan makes the testing more effective and efficient. • A test plan outlines the entire testing process and includes individual test cases. • A test plan consists of the following components: • Test Scenario: The plan for testing each module in an application is called a test scenario. • Test Cases: Testing for every possible input value is almost an impossible task so testing can be done for some representative inputs, which are called test cases. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 41 of 50
  • 42. Exception Handling, Debugging and TestingWindows ApplicationsImplementing Tracing • Tracing is a technique that allows you to log informative messages about an application’s conditions at run time. • Using tracing, you can get informative messages about the execution of your application without interrupting the application execution even after it has been deployed. • There are three phases of code tracing: • Instrumentation: In the instrumentation phase, trace code is added to your application. • Tracing: In the tracing phase, the tracing code writes information about the execution of the application to the specified target. • Analysis: In the analysis phase, tracing information is evaluated to identify and understand problems in the application. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 42 of 50
  • 43. Exception Handling, Debugging and TestingWindows ApplicationsUsing the Debug and Trace Classes • The System.Diagnostics namespace contains the Debug and Trace classes that include Shared methods which can be used to test conditions at run time and log the results. • The Debug class is mainly used in the development phase for debugging. • The Trace class is used for testing and optimization even after an application is compiled and released. • The six Debug and Trace methods that write tracing information are listed below: • Assert • Fail • Write • WriteLine • WriteIf • WriteLineIf ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 43 of 50
  • 44. Exception Handling, Debugging and TestingWindows ApplicationsWorking with Listeners • The Listeners collection includes classes that can receive output from the Shared methods of the Trace and Debug classes. • Each member of the Listeners collection collects, stores, and routes tracing messages. • There are three types of predefined listeners: • DefaultTraceListener: It is an instance of the DefaultTraceListener class and is a default member of the Listeners collection. • TextWriterTraceListener: It is an instance of the TextWriterTraceListener class and it redirects trace output to an instance of the TextWriter class or to a Stream object. • EventLogTraceListener: It is an instance of the EventLogTraceListener class and it redirects trace output to an event log. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 44 of 50
  • 45. Exception Handling, Debugging and TestingWindows ApplicationsLogging Trace Output to Text Files • The TextWriterTraceListener class is used to log trace output to text files. • To log trace output to a text file, the following steps must be performed: 1. Create an instance of a FileStream object that specifies the appropriate text file. Dim myFile As New System.IO.FileStream _ (“C:myFile.txt”, IO.FileMode.OpenOrCreate) 4. Create an instance of TextWriterTraceListener that specifies the new FileStream object as its target. Dim myListener As New TextWriterTraceListener(myFile) 6. Add the new listener to the Trace.Listeners collection. Trace.Listeners.Add(myListener) flush the Trace buffer by calling the Flush method to write output to the text file. Trace.Flush() ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 45 of 50
  • 46. Exception Handling, Debugging and TestingWindows ApplicationsLogging Trace Output to an EventLog • You use the EventLogTraceListener class to log the trace output to an EventLog object. • To log the trace output to an EventLog, the following steps must be performed: 1. Create an instance of a EventLog object and assign it to a new event log or an existing event log. Dim myLog As New EventLog (“Event Log”) 2. Set the Source property of the EventLog. myLog.Source = “Trace Output” 3. Create an instance of EventLogTraceListener that specifies the new log as its target. Dim myListener As New EventLogTraceListener(myLog) 4. Add the new listener to the Trace.Listeners collection. Trace.Listeners.Add(myListener) ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 46 of 50
  • 47. Exception Handling, Debugging and TestingWindows ApplicationsImplementing Trace Switches • Trace switches allow you to enable, disable, and filter tracing output. • Two types of trace switches are provided in the .NET Framework: • BooleanSwitch Class: The BooleanSwitch class acts as a toggle switch that may either enable or disable a variety of trace statements. • TraceSwitch Class: The TraceSwitch class allows you to enable a trace switch for a particular tracing level. • To use the BooleanSwitch or the TraceSwitch class you need to create an instance of these classes. • The TraceSwitch class exposes four read-only properties that represent the Trace levels. These are: • TraceSwitch.TraceError Property • TraceSwitch.TraceWarning Property • TraceSwitch.TraceInfo Property • TraceSwitch.TraceVerbose Property ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 47 of 50
  • 48. Exception Handling, Debugging and TestingWindows ApplicationsSummary In this lesson, you learned that: • The types of errors that can occur in an application are syntax errors, run- time errors, and logical errors. • An exception is an abnormal condition that an application encounters during execution. • Exception handling is the process of providing an alternate path to be executed when the application is not able to execute in the desired way. • Visual Basic .NET provides two methods to handle exceptions: • Structured exception handling • Unstructured exception handling • In addition to handling pre-defined exceptions, users can create their own exceptions by deriving an exception class from the ApplicationException class. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 48 of 50
  • 49. Exception Handling, Debugging and TestingWindows ApplicationsSummary (Contd.) • Once an application has been coded, it must be tested to ensure that it fulfills the requirements for which it was designed and meets quality expectations. • There are various types of testing that an application has to go through. These include unit testing, integration testing, regression testing and acceptance testing. • For testing to be successful, a test plan must be created that outlines the entire process of testing and includes budget, schedule and performance considerations. • In order to assist you in debugging logical and runtime errors, Visual Basic .NET provides extensive debugging tools. You can use the Visual Basic .NET Debug toolbar to access these tools. • By using the debugging tools, you can perform the following actions: • Start execution • Step through execution • Stop execution ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 49 of 50
  • 50. Exception Handling, Debugging and TestingWindows ApplicationsSummary (Contd.) • You can log informative messages about your application’s conditions at run time by using tracing. • Tracing can be implemented by using the Trace and Debug classes. • The Listeners collection is a group of classes capable of receiving output from the Debug and Trace classes. • Trace switches allow you to enable, disable, and filter tracing output. • Conditional compilation is a means of selectively compiling portions of your program code. This can be used for creating multiple versions of your application without the need to maintain multiple copies of code. ©NIIT Enhancing and Distributing Applications Lesson 1B / Slide 50 of 50

×