13.1 Overview of the .NET Framework
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13.1 Overview of the .NET Framework - A component is an encapsulation of software that can stand by itself and be used by other components - .NET is based in in part its predecessor, COM - .NET Framework is a collection of technologies

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13.1 Overview of the .NET Framework - A component is an encapsulation of software

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13 1 overview of the net framework a component is an encapsulation of software

13.1 Overview of the .NET Framework

- A component is an encapsulation of software

that can stand by itself and be used by other

components

- .NET is based in in part its predecessor, COM

- .NET Framework is a collection of technologies

for the development and deployment of .NET

software systems

- The .NET Common Language Runtime (CLR)

- Assembly integrity checking – using a hash

code

- JIT compilation

- Garbage collection – can be forced

- Exception handling

- .NET languages from Microsoft:

VB .NET

Managed C++ .NET

JScript .NET

J# .NET

C#

+ many more from other sources


13 1 overview of the net framework a component is an encapsulation of software

13.1 Overview of the .NET Framework

(continued)

- .NET languages from Microsoft:

VB .NET

Managed C++ .NET

JScript .NET

J# .NET

C#

- There are now >20 .NET languages, including

COBOL, Fortran, Perl, and Python

- Every .NET language has a compiler that

produces IL, which is JIT compiled to machine

code

- There is no IL interpreter

- Advantage of multi-language systems:

- Can use old components

- Easy transition to .NET

- Disadvantage of multi-language systems:

- Maintenance is difficult


13 1 overview of the net framework a component is an encapsulation of software

13.1 Overview of the .NET Framework

(continued)

- Common Language Infrastructure (CLI)

- Common Type System (CTS)

- Minimum type set for .NET

- All .NET languages must support them

- e.g., Int32, which corresponds to int in C#

- All CTS types are derived from System.object

- Two categories of data types: value and

reference

- Common Language System (CLS)

- Minimum language constructs and rules

- e.g., no operator overloading, no pointers,

identifiers are not case sensitive, etc.

- Framework Class Libraries (FCL)

- > 4000 classes


13 1 overview of the net framework a component is an encapsulation of software

13.1 Overview of the .NET Framework

(continued)

- Aim of CLI and CLR: interoperability

- A component in any .NET language can:

- Inherit from any other .NET language class

- Call the methods of any other .NET language

class

- Subclass any class from any .NET language


13 1 overview of the net framework a component is an encapsulation of software

  • 13.2 Introduction to C#

  • - C# heritage:

  • - From Java:

  • - Single inheritance

  • - Interfaces

  • - Garbage collection

  • - No global types or variables

  • - Level of coercion

  • - From C++:

  • - Pointers

  • - Operator overloading

  • - Preprocessor

  • - structs, enums, …

  • - From Delphi and VB:

  • - Properties

  • - From J# (actually, J++):

  • - Delegates


13 1 overview of the net framework a component is an encapsulation of software

13.2 Introduction to C# (continued)

- C# heritage (continued):

- New Features:

- Indexes

- Attributes

- Events

- A safer switch statement

- A new kind of struct

- Primitive Types and Expressions

- Similar to Java, except C# has unsigned integers,

a 16-byte decimal type, and pointers

- Data Structures

- Similar to Java and C++: class library support for

Array, ArrayList, Queue, and Stack

- Array class has many methods and a Length

property

- An enumeration type, similar to that of C++,

except no coercions to or from other types


13 1 overview of the net framework a component is an encapsulation of software

13.2 Introduction to C# (continued)

- Control Statements

- Like Java, except:

1. There is a goto,

2. There is a foreach statement

foreach (int myInt in myIntArray) { … }

3. The switch has a static semantics rule that

requires each selectable segment to end in an

unconditional transfer (either break or goto)

case 0:

Zeros++;

goto case 1;

case 1:

- Classes, Methods, and Structures

- Like Java, except:

1. Parameters can be passed by value (default),

passed by reference, or passed by result

- Pass by reference - ref

- Pass by result - out


13 1 overview of the net framework a component is an encapsulation of software

13.2 Introduction to C# (continued)

2. A method that can be overriden must be marked

virtual

A method that overrides must be marked

override

A method that has the same protocol as an

inherited method but is NOT to override it is

marked new

3. A method can take a variable number of

parameters, if they are the same type

void SumInts(params int[] intValues) { … }

int [] myIntArray = new int[6] {2, 4, 6,

8, 10, 12};

...

sum1 = SumInts(myArray);

sum2 = SumInts(10, i, 17, k);

4. A C# struct is a lightweight class

- Supports constructors and can implement

interfaces

- Does not support inheritance or subclasses

- Is allocated from the stack


13 1 overview of the net framework a component is an encapsulation of software

13.2 Introduction to C# (continued)

- Properties

A property is a special data field of a class that can

provide implicitly called get and set accessors

public class Weather {

public int DegreeDays {

get {

return degreeDays;

}

set {

degreeDays = value;

}

private int degreeDays;

} //** end of property DegreeDays

...

} //** end of class Weather

...

Weather w = new Weather();

..

w.degreeDays += degreeDaysToday;

- Delegates – object-oriented method pointers

public delegate void AHandler (

object o, System.EventArgs e);

AHandler can reference any method with this

protocol


13 1 overview of the net framework a component is an encapsulation of software

13.2 Introduction to C# (continued)

- Program Structure

- System is a namespace of FCL that provides

input & output, string manipulation, threading,

and collections

- Abbreviations of elements of System are

premitted by:

using System;

Complete program example:

using System;

public class myTester {

public static void Main() {

Console.WriteLine(″Howdy!″);

}

}

- File Storage for Programs

- A file can store any number of public classes

and/or interfaces

- Every class can define a Main method, but if

there are more than one in a file, you must tell

the system where to begin


13 1 overview of the net framework a component is an encapsulation of software

13.3 Introduction to ASP.NET

-The Basics of ASP.NET

- Based on ASP, but revolutionarily different

- ASP documents could have embedded scripts in

either Jscript or VB – both purely interpreted

- Disadvantages:

1. Inefficient

2. Mixing script and markup is confusing

3. Scripting languages are unreliable

- ASP.NET differs from JSP in two ways:

1. Any .NET language can be used

2. All ASP.NET code is compiled

- Code can be embedded in ASP.NET documents,

or can be separate in a code-behind file

- Every ASP.NET document is compiled into a

class

- Base class is System.Web.UI.Page, unless there

is a code-behind class (then it is the base)


13 1 overview of the net framework a component is an encapsulation of software

13.3 Introduction to ASP.NET (continued)

- ASP.NET documents

- Can include:

1. XHTML markup

2. Directives – appear in <% … %> blocks

3. Render blocks <% … %>

- No method definitions

- Put into a function in the document class

4. Declaration blocks

- Script elements - method definitions

5. Server-side comments <%-- … --%>

- The only directive covered here is @Page

- The only necessary attribute is Language

 SHOW ex1.aspx

- Code-behind Files

- The @Page directive must specify the code-behind

file in a Inherits attribute

- If you want the code-behind file implicitly

compiled, include a Src attribute

 SHOW ex2.aspx and ex2.aspx.cs


13 1 overview of the net framework a component is an encapsulation of software

13.4 ASP.NET Controls

- Two collections of server controls:

HTML controls and Web controls

- HTML Controls

- One-to-one correspondence with the XHTML

elements

HtmlInputButton - <input type = ″submit″ …/>

HtmlInputRadioButton - <input type = ″radio″

- Difference between XHTML elements and their

corresponding HTML controls:

- Server-side code can interact with HTML

controls

- Many HTML controls can raise events

- ServerClick and ServerChange

- Any element that will be used by server-side code

must include the runat = ″server″ attribute

- A form that has server-side elements must also

include the runat = ″server″ attribute

- Some HTML controls are not form elements


13 1 overview of the net framework a component is an encapsulation of software

13.4 ASP.NET Controls (continued)

<form runat = ″server″>

<input type = ″text″ id = ″address″

runat = ″server″ />

</form>

- The form has no action attribute

- The server-side code (the document class) would

have:

protected HtmlInputText address;

- All HTML controls are converted to objects in the

document class

- An ASP.NET document with a form has two

purposes:

1. Describe the form to be displayed by the

browser

2. Process the form when its data is submitted

- Each of these has its own kind of request –

initial and postback

 SHOW ex3.aspx (after the form is filled)


13 1 overview of the net framework a component is an encapsulation of software

13.4 ASP.NET Controls (continued)

- Document classes maintain form data state

between postbacks

- In the ViewState hidden element of the form

- The life of an ASP.NET document:

1. The client requests the document

2. A document class is created by compiling the

requested document; then its constructor is

called

3. The control state of the document is initialized

with ViewState

4. Request form data is used to set the control state

5. The current control state is saved in ViewState

6. The instance is executed and the results are

returned to the client

7. The class and its instance are deleted on the

server

8. The client interacts with the form

9. The client causes a postback

10. A document class is compiled and its

constructor is called

11. The control state is initialized from ViewState

12. The control state is set with the form data

13. The current state is saved in ViewState

14. The instance is executed and the results are

returned to the client

 SHOW ex3.aspx


13 1 overview of the net framework a component is an encapsulation of software

13.4 ASP.NET Controls (continued)

- There are two levels of events – control events

and page-level events

- Four page-level events are implicitly raised

during the process of processing a request

Load, Unload, PreRender, and Init

- There are two ways to write and register handlers

for these events

1. Write handlers with preassigned names and

a specific protocol – implicitly registered

public void Page_Init(System.EventArgs e)

{ … }

- Called auto event wireup

2. Overload virtual methods and manually

register them

- Control Events

- ServerClick and ServerChange

- Two ways to write and register handlers


13 1 overview of the net framework a component is an encapsulation of software

13.4 ASP.NET Controls (continued)

1. Write them as functions and register them in

the XHTML

(OnServerClick and OnServerChange)

- The protocol for control event handlers is

protected void TextBoxHandler (

object src, System.EventArgs e) { ... }

<input type = ″text″ id = ″Name″

OnServerChange = ″TextBoxHandler″

runat = ″server″ />

2. The second way to register a control event

handler is to use the standard CLR approach

- Write the handler, as before

- Create a handler delegate instance, passing

the name of the handler to the constructor

- Subscribe the new delegate instance to the

control and the event name

protected void Page_Init(

object src, EventArgs e) {

Name.ServerChange +=

new EventHandler(TextboxHandler);

}


13 1 overview of the net framework a component is an encapsulation of software

13.4 ASP.NET Controls (continued)

- Revised list of what happens:

1. Client requests the document

2. A document class is compiled and its

constructor is called

3. The Page event Init is raised

4. The control state of the instance is initialized with

ViewState

5. The form data is used to initialize the control state

6. The Page event Load is raised

7. Server-side control events are raised

8. The Page event PreRender is raised

9. The current control state of the instance is

saved in ViewState

10. The instance is executed and the results

returned to the client

11. The Page event Unload is raised

12. The class and its instance are deleted on the

server

- Web Controls

- A larger and richer collection than the HTML

controls – based on those of VB

- A weaker connection to the XHTML elements


13 1 overview of the net framework a component is an encapsulation of software

13.4 ASP.NET Controls (continued)

- A more consistent programming interface

- Web controls include:

- Xml – allows the inclusion of XSL

transformations

- Panel – allows collections of elements to be

handled together (placement, etc.)

- AdRotator – Easy way to have different content

appear on different requests

- Validator controls – later

- Controls can be created by either markup or by

programming code

- For example,

<asp.button id = ″helpButton″ Text = ″help″

OnClick = ″OnClickHandler″

runat = “server” />

-


13 1 overview of the net framework a component is an encapsulation of software

13.4 ASP.NET Controls (continued)

protected Button helpButton = new Button();

helpButton.Text = ″help″;

helpButton.id = ″helpButton″;

helpButton.OnClick = ″OnClickHandler″;

helpButton.runat = ″server″;

- There are two problems with doing it this way:

1. It required more typing

2. Placement of the control in the document is

cumbersome

- Can use a placeholder

<asp:placeholder id = ″buttonPlace″

runat = ″server″ />

buttonPlace.Controls.Add(helpButton);

- Although creating elements is easier with

markup, modifying them is a good use of code

- Example: put the list items in a drop down list

with code


13 1 overview of the net framework a component is an encapsulation of software

13.4 ASP.NET Controls (continued)

- Response output from controls

- Can’t use Response.Write, because the output

goes to the beginning of the buffer, rather than

close to the controls

- Alternative:

- Create a label element where you want the

output to appear

- Set the content of the label by assigning to

its Text property

- Use string.Format for output with text and

values

<asp:label id = ″output″

runat = ″server″ />

<% string msg = string.Format{

″The result is {0} <br />″, result);

output.Text = msg; %>

 SHOW ex4.aspx and ex4.aspx.cs


13 1 overview of the net framework a component is an encapsulation of software

13.4 ASP.NET Controls (continued)

- Validation Controls

- There are six; the most commonly used four:

- RequiredFieldValidator

- CompareValidator

- RangeValidator

- RegularExpressionValidator

- Validation controls are placed just after the

controls whose values they are to validate

- Use the ControlToValidate attribute to specify

the control to be validated

- Use the ErrorMessage attribute to specify the

error message

 SHOW ex5.aspx


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