Chapter 4. Exception Handling

Chia sẻ: Nguyen Quoc Khanh | Ngày: | Loại File: PPT | Số trang:10

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An exception is any error condition or unexpected behavior encountered by an executing program. Exceptions can be raised because of a fault in your code or in code you call (such as a shared library), unavailable operating system resources, unexpected conditions the common language runtime encounters (such as code that cannot be verified), and so on.

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Nội dung Text: Chapter 4. Exception Handling

Chapter 4. Exception Handling A reference of MSDN Library for Visual Studio 2005 Hoàng Hữu Việt IT Faculty, Vinh University
Contents Introduction Chapter 4. Exception Handling  Exception Class  Try statement  Example  Slide 2
Introduction An exception is any error condition or Chapter 4. Exception Handling  unexpected behavior encountered by an executing program. Exceptions can be raised because of a fault  in your code or in code you call (such as a shared library), unavailable operating system resources, unexpected conditions the common language runtime encounters (such as code that cannot be verified), and so on. Slide 3
Introduction In the .NET Framework, an exception is an Chapter 4. Exception Handling  object that inherits from the Exception Class class. An exception is thrown from an area of code where a problem has occurred. The exception is passed up the stack until the application handles it or the program terminates. Slide 4
Exception Class The Exception class is the base class from Chapter 4. Exception Handling  which exceptions inherit. Most exception objects are instances of some derived class of Exception, but you can throw any object that derives from the Object class as an exception. Slide 5
Exception Class Common Properties Chapter 4. Exception Handling  Message: Provides details about the cause of an  exception. StackTrace: Contains a stack trace that can be  used to determine where an error occurred. The stack trace includes the source file name and program line number if debugging information is available. Slide 6
Try statement A common usage of catch and finally Chapter 4. Exception Handling  together is to obtain and use resources in a try block, deal with exceptional circumstances in a catch block, and release the resources in the finally block Slide 7
try statement try ...catch ... finally Statement Chapter 4. Exception Handling  try { 1. Include codes in which exceptions might occur. } catch (Exception ) { 2. Represent types of exceptions the catch can handle. } finally { 3.(Optional) codes present here will always execute. } Slide 8
Example Example: Divide by zero Chapter 4. Exception Handling  Error Message Error Message Slide 9
Example Code pattern Chapter 4. Exception Handling  private void btnDivide_Click(object sender, EventArgs e) { textBox3.Clear(); try { int a = Convert.ToInt32(textBox1.Text); int b = Convert.ToInt32(textBox2.Text); int c = a / b; textBox3.Text = c.ToString(); } catch(Exception ex) { MessageBox.Show(ex.Message); } } Slide 10