1. From Debugging to Data Conversion Operations
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2. Collapsing Code
#region … #endregion
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3. Code Outlining
Code files may contain definitions for one or more classes, structures, interfaces, or other code entities
The files may become quite large, ranging into the hundreds or thousands of lines of code
When they do become this long, programmers often find it tedious to “find” or “navigate” to the right place in the file on which to work
Moving back and forth between locations can become tedious
For example, moving between the definition of an item and a place at which it is referenced may involve scrolling hundreds or thousands of lines
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4. Can jump to previous or next bookmark
Code Outlining
Visual Studio provides a number of features that can help navigation in a large source file
Visual Studio allows you to bookmark individual lines of code
Can jump to previous or next bookmark
Bookmark
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5. Code Outlining
Another feature that aids developers in navigating large code files is code outlining
Regions of code may be designated
Each region may be collapsed into a single line in the code editor
Collapsed regions may be expanded to reveal their detail whenever the detail is needed
Some regions are “automatically” designated for you including
Method definitions
XML comment blocks
Classes
Namespaces
and more
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6. Code Outlining Region designators Region designators Odds and Ends
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7. Code Outlining
Clicking on one of the minus signs will collapse the associated region and replace the minus with a plus (for later expansion)
Note that the namespace and class may also be collapsed
Each collapsed region becomes a single line
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8. Designating Other Regions
The developer may use #region and #endregion preprocessor directives to mark the beginning and end of a region that is not automatically so designated by Visual Studio
For example, in a large class, there may be several overloaded constructor methods (the String class has 8 overloaded constructor methods)
One may use the #region … #endregion directives to designate all of them as one large region
One can then collapse or expand all constructors at once
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9. #region … #endregion The syntax of these preprocessor commands is
#region Title Phrase
. . .
#endregion
The #region and #endregion commands must be paired
Regions may be nested but not overlapping
The Title Phrase will be displayed when the region is collapsed
One is not limited to using regions that correspond to large blocks of code such as methods or classes
One may use these commands anywhere within reason – including turning a logical segment of a method into its own region
One may use the Surrounds With … capability discussed earlier to embed a selected existing segment of code with #region … #endregion
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10. Can be collapsed to this small segment
Example
Three new regions added, each of which has two or three regions already collapsed inside it
Can be collapsed to this small segment
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11. Regions
It is usually considered to be good practice to use nested regions in a reasonable way to allow developers to
See the big picture when all are collapsed
Expand only what we need to work on now
Obviously, this can be taken too far …
One doesn’t want to nest so deeply one has to spend excessive time collapsing and expanding
Don’t create a region for each line of code or anything nearly that excessive
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12. Reference Highlighter
When one instance of an identifier is selected …
… others are highlighted too
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13. Named and Optional Parameters in C# 4.0
New in Visual Studio 2010, .NET 4.0
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14. Passing Parameters
When passing parameters to a method, one must usually pass all of them in exactly the same order as specified by the method definition
When the number of parameters is large, this requirement is a source of errors, and it is tedious to the developer – even though Intellisense is great helper
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15. Named Parameters
Named parameters allow you to call a method by specifying which argument in a method call refers to which formal parameter. Example:
public static int Subtract (int left, int right) {
return (left – right); }
All three of these calls are equivalent:
result = Subtract (7, 5); // left is 7, right is 5
result = Subtract (left: 7, right: 5); // left and right
result = Subtract (right: 5, left: 7); // are clearly designated
If you don't specify a name, the normal order is used
Parameters can be specified by name in any order
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16. Optional Parameters
Optional parameters enable you to specify a default value for a parameter in a method
Omitting a parameter with a default value in a method call results in the default value being used
Providing a value for a default parameter when calling a method overrides the default value
Any parameters that have default values must be at the right end of the argument list
The first parameter with a default value must follow all parameters that do not have default values
The default values for optional parameters must be compile-time constants
One may not create new objects, use static variables, or use method returns as a default parameter value
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17. Optional Parameters
You specify a default value for an optional parameter by declaring its value in the method definition
For example, one might update the Subtract method to have a default behavior of subtracting 1
public static int Subtract (int left, int right = 1) {
return left - right; }
The following call decrements count
count = Subtract (count);
Optional and named parameters work together to provide a richer calling sequence. Callers can specify none, any, or all of the optional parameters by name.
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18. Note default parameters: customer, description, and p
Example
Note default parameters: customer, description, and p
If description is null, set Description property to empty string – else set it to description
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19. Type conversion Casting and conversion methods Odds and Ends
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20. Data Types and Conversions
Two items may be of compatible or incompatible types
An integer is compatible with a double because both are numeric and an integer can be converted into a double without loss of data
“Ken” is a string that cannot be converted into a double in any intuitive way; the two types are not compatible
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21. Implicit/Explicit Conversions
For compatible types, there may or may not be implicit conversions from one type to another
Depends on whether the compiler knows how to make the conversion
Depends on whether there is a potential for loss of data
Example, the following produces an implicit conversion from the integer on the right-hand-side to the double on the left. No data loss is possible.
If there is a possibility of data loss, an explicit operation is required: the programmer must ask for a conversion
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22. Explicit Conversions
One way to request a conversion is to cast between compatible types
A cast operation may be an acknowledgement of possible data loss and “it is OK with me”
May be a statement that “I know the object is really of this other type and it is OK to treat it that way”
Casting as string means we can use string methods and string properties
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23. Casting The form for requesting a cast is (new type) item
Item must be of a type compatible with the requested type so that a conversion is possible
If, at run time, it is determined that one cannot make the requested conversion, an exception is thrown
For example, an array of Object may contain any types of items such as strings, doubles, PigLatin objects, Employee objects, etc. If we try to cast and use one of the items as a string, that will work only if that particular item is a string rather than one of the other types of items; it will fail for a double or an Employee object.
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24. Casting Casting is a “temporary” operation
It does not permanently change the type of data being cast
Internally, C# makes a temporary variable of the converted type and converts the item being cast into the temporary variable
The value in the temporary is used for the rest of the operation – at which time it ceases to exist
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25. Casting
An object of a derived class isa object of its base class (an Employee isa Person), but the reverse is not true (some Persons are not Employees)
Casting is required when an object is defined to be of a base type, but it actually refers to a derived type of object
To use the methods and properties of the derived type, one must first cast the object to that type
The casting is OK because the object really is of the derived type
See the Object array example several slides back.
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26. Using “as” to Cast to a Different Type

27. Check to see if the as cast was successful
The as Keyword
The as operator provides a type of casting operation
Ordinary cast operations throw an exception if the cast is not valid
If the conversion is not possible, as returns null instead of raising an exception
Use of the as keyword
Check to see if the as cast was successful

28. Was the as cast successful?
Another as Example
Trying to cast as a string. It works on those items that are strings, but returns null otherwise
Was the as cast successful?
Results

29. Other Explicit Conversions
Casting can only be used in cases in which the types are compatible and the compiler knows how to do the conversion
There are cases in which a conversion is needed but a cast cannot be done
Example: To input a salary from the keyboard, one may use Console.ReadLine ( );
This inputs a string, hopefully the string representation of a number such as “ ”
We cannot cast this string as a Decimal or a Double however since they are incompatible types
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30. Explicit Conversions
Explicit Conversions that cannot be done by casting require the programmer to invoke a method to do the conversion
Example 1:
char [ ] cArray = strVowels.ToCharArray ( );
is used to convert a string into an array of characters
Example 2:
string strLine = MyTrip.ToString ( );
may convert a decimal MilesPerGallon object to a string
Any class may have methods that convert objects of some other type to its type or vice versa
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31. String to Numeric Conversions
The standard .NET numeric data types such as Int32, Double, Decimal, and so forth have static methods named Parse
Each takes a string argument – the string representation of a number of that type
Method converts the value argument to the appropriate numeric type
Example:
Throws exception if the string cannot be parsed as the specified type
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32. String Conversions
To avoid exceptions in cases where the Parse argument is invalid, use TryParse
public static bool TryParse ( string s, out double result )
Works similar to Parse, but returns true or false to indicate whether it was successful
If it was successful, the second argument has the result in it
out specifies that the argument need not have a value going in because the method will assign one to be returned
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33. Example: String Conversions
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34. Conversion between numeric types
Conversion from one numeric type to another is typically done implicitly (if appropriate) or by casting (if needed)
However, .NET numeric structs have conversion methods
Example: Decimal has the following methods
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35. Visual Studio Debugger
Elementary Debugging Tools in VS
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36. Debugging Three types of errors that developers see frequently
Syntax errors: compile time issues
Execution time program crashes
Program logic errors – program runs successfully but does not produce desired results
The debugger is a set of tools that can be used to
monitor a running program
inspect object values during execution
collect execution history so that at any point we know how we got to that point
and more
The debugger may be used to help the developer gather information need to deal with runtime errors, not syntax errors
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37. VS Debugger
The debugger can be used for some quite sophisticated debugging situations such as
Distributed solutions with parts running on separate computers in diverse locations
Parallel algorithms running on multiple processors within a single computer (or super computer)
Debug suspected bugs within VS itself
Monitor memory, registers, and other hardware features
The discussion here is limited to much more common debugging scenarios
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38. “Watching Code Run”
To use the debugger’s features, execution must be started with “Start Debugging”
Start Debugging
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39. Code Breakpoints
In debug mode, one may pause program execution at a specified point called a breakpoint
Once paused, one can inspect the current values of variables, properties, and so forth
One may step through subsequent instructions one at a time
One may inspect program history to determine what execution path led to this point (a method may have been called from many different places, for example, and it may be helpful to where it was called this time)
One may even modify something and continue
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40. Click here to toggle the breakpoint on/off
Breakpoints
The easiest way to set a breakpoint on or off is to click in the margin to the left of the line number
Click here to toggle the breakpoint on/off
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41. Breakpoints One may set as many breakpoints as desired
When execution reaches a breakpoint
Execution pauses at that line (it has not been executed - yet)
Program runs full speed up to the first breakpoint
At the breakpoint, one may inspect the values of objects as they are at that point in the program
Easiest way to do this is to hover over the object with the cursor, and a tool tip will reveal the value
For a complex object such as an array, one may have to expand the tool tip to see the details
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42. Example Yellow arrow marks place where execution is paused
Tooltip shows current value of strFrom – line 20 has not been executed yet.
Hovering over a different variable shows its value – as of line 20
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43. Debugging Toolbar Continue to next breakpoint
Stop debugging and resume editing
Restart the debugging session
Highlight next instruction to be executed
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44. Debugging Toolbar, cont.
Step Into – a method one is trying to execute on this line – to watch it run, a line at a time
Step over – execute the line at full speed but pause on the following line
Step Out Of – execute rest of this method and return to the calling method; most useful when in code you did not write
Display a value in hexadecimal so one can see its internal form
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45. Step Through Code and Watch it Run
Execution point moves to next line and result of the executed line can be observed
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46. Where that method was called
Call Stack
The Call Stack shows the program’s execution history
For example:
This shows we got to the MilesPerGallon constructor from a call to it on Line 17 of Main
Where we are now
Where that method was called
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47. Locals Watch
The Locals Watch window shows values of all locally defined variables at the point in time where execution is temporarily frozen
Stepping through allows one to watch these values change
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48. Autos Watch
The Autos Watch Window shows information similar to the Locals Watch Window
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49. Disassembly
One can even see the pseudo assembly language code that has been generated …
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50. More On Breakpoints
Right-clicking on a breakpoint brings up a context menu that allows one to make breakpoints work in more sophisticated ways
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51. Conditional Breakpoints
Sometimes, a breakpoint may be in a loop and you may not want to pause every time through the loop, but you do want to break on specific passes
Specify a condition that determines when to break
User-specified condition
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52. Conditional Breakpoints
You may want to stop after the breakpoint is hit a certain number of times
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53. Conditional Breakpoints
You may also specify action other than pausing when a breakpoint is hit
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54. Intellitrace
Using the techniques described so far, one may watch a program run, examining variable values as the program advances
One can only go forward in execution or quit debugging after a pause
One cannot go backward if the result of some previous step has been forgotten
Intellitrace is a new feature of VS2010 that allows one to move backwards as well as forward
Intellitrace “records” the state of the program as it executes
One may “back up” and review a previously recorded state
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55. Using Intellitrace Only available for x86 target output
To set the target, right click on project and choose Properties from the context menu
On the Build tab, choose x86 CPU target
Choose x86
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56. Open the Intellitrace Window
Using Intellitrace
Open the Intellitrace Window
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57. Intellitrace Event Window
Hit breakpoint line 32 in Main
Stepped to next line
Entered ctor on line 54
Stepping one line at a time … at line 60 now
Now we can click on any line here to review the state at that point in the execution
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58. Current line where execute is paused
Icons
Intellitrace Icons
Current line where execute is paused
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