Inside Methods in visual studio .net

Often you'll want to have more than one method with the same name. The most common example of this is to have more than one constructor with the same name, which allows you to create the object with different parameters. For example, if you were creating a Time object, you might have circumstances where you want to create the Time object by passing in the date, hours, minutes, and seconds. Other times, you might want to create a Time object by passing in an existing Time object. Still other times, you might want to pass in just a date, without hours and minutes. Overloading the constructor allows you to provide these various options.

It would be convenient also to allow the client to create a new Time object by passing in year, month, date, hour, minute, and second values. Some clients might prefer one or the other constructor; you can provide both and the client can decide which better fits the situation.

In order to overload your constructor, you must make sure that each constructor has a unique signature. The signature of a method is composed of its name and its parameter list. Two methods differ in their signatures if they have different names or different parameter lists. Parameter lists can differ by having different numbers or types of parameters.

Encapsulating Data with Properties :

It is generally desirable to designate the member variables of a class as private. This means that only member methods of that class can access their value. You make member variables private to support data hiding, which is part of the encapsulation of a class.

Object-oriented programmers are told that member variables should be private. That is fine, but how do you provide access to this data to your clients? The answer for C# programmers is properties. Properties allow clients to access class state as if they were accessing member fields directly, while actually implementing that access through a class method.

This is ideal. The client wants direct access to the state of the object. The class designer, however, wants to hide the internal state of the class in class fields and provide indirect access through a method. The property provides both: the illusion of direct access for the client and the reality of indirect access for the class developer.

By decoupling the class state from the method that accesses that state, the designer is free to change the internal state of the object as needed. When the Time class is first created, the Hour value might be stored as a member variable. When the class is redesigned, the Hour value might be computed or retrieved from a database. If the client had direct access to the original Hour member variable, the change to computing the value would break the client. By decoupling and forcing the client to go through a property, the Time class can change how it manages its internal state without breaking client code.

In short, properties provide the data hiding required by good object-oriented design.

Returning Multiple Values

Methods can return only a single value. But this isn't always convenient. Let's return to the Time class. It would be great to create a GetTime() method to return the hour, minutes, and seconds. You can't return all three of these as return values, but perhaps you can pass in three parameters, let the GetTime() method modify the parameters, and then examine the result in the calling method, in this case Run().

Passing by Value and by Reference

C# divides the world of types into value types and reference types. All intrinsic types (such as int and long) are value types. Classes are reference types.

When you pass a value type (such as an int) into a method, a copy is made. When you make changes to the parameter, you make changes to the copy. Back in the Run() method, the original integer variables, theHour, theMinute, and theSecond are unaffected by the changes made in GetTime().

What you need is a way to pass in the integer parameters by reference. When you pass an object by reference, no copy is made. A reference to the original variable is passed in. Thus when you make changes in GetTime(), the changes are also made to the original variables in Run().

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DAY 1 MICROSOFT DOT NET FRAME WORK

DAY 2 MICROSOFT DOT NET BASE CLASS LIBRARY

DAY 3 MICROSOFT DOT NET CLASSES AND STRECTURES

DAY 4 METHODS IN FRAME WORK

DAY 5 INPUT VALIDATIONS IN DOT NET PART ONE

DAY 6 INPUT VALIDATIONS IN DOT NET PART TWO

DAY 7 DATA TYPES IN DOT NET

DAY 8 DATA TYPES IN DOT NET PART TWO

DAY 9 IMPLEMENTING PROPERTIES IN DOT NET

DAY 10 DELEGATES AND EVENTS

DAY 11 OOPS INTRODUCTION

DAY 12 POLYMORPHISM

DAY 13 INHERITANCE AND POLYMORPHISM

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DAY 15 DEBUG AND TRACE IN CLASSES

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DAY 19 ADO.NET INTRODUCTION

DAY 20 DATA ACCESSING IN DOT NET

DAY 21 DATA BASE OBJECTS

Methods in .net frame work

You can add methods as members to your classes. Methods represent actions your class can take. Methods generally come in two varieties: those that return a value (functions in Visual Basic) and those that do not return a value (Subs in Visual Basic).

The following code shows an example of both kinds of methods:

Visual Basic .NET

Public Sub MySub()
MessageBox.Show("This is a non-value returning method")
End Sub

Public Function Add(ByVal first as Integer, ByVal second as _
Integer)
Dim Result as Integer
Result = first + second
End Function

Visual C# makes no distinction between methods that return a value and methods that do not. In either case, you must specify the return value type. If the method does not return a value, its return type is void. Here are examples of C# methods:

Visual C#

public void myVoidMethod()
{
MessageBox.Show("This method doesn't return a value");
}
public int Add(int first, int second)
{
int Result;
Result = first + second;
}

Calling Methods:

A method does not execute until it is called. You can call a method by referencing its method name along with any required parameters.

Visual Basic .NET

' This line calls the Rotate method, with two parameters
Rotate(45, "Degrees")

Visual C#

// This line calls the Rotate method, with two parameters
Rotate(45, "Degrees");

The Main method is a special case. It is called upon initiation of program execution. Destructors, another special case, are called by the run time just prior to the destruction of an object. Constructors, a third special case, are executed by an object during its initialization.

Method Variables:

Variables declared within methods are said to have method scope. This means that once the method completes execution, they are destroyed and their memory reclaimed. They are said to have gone out of scope.

Variables within smaller divisions of methods have even more limited scope. For example, variables declared within a For-Next (for) loop are accessible only within the loop.

Visual Basic allows you to create method variables that are not destroyed after a method finishes execution. These variables, called static method variables, persist in memory and retain their values through multiple executions of a method.

Although this variable persists in memory, it is still only available during execution of this method. You would use a static variable for a method that needed to keep track of how many times it had been called.

Parameters:

A method can take one or more parameters. A parameter is an argument that is passed to the method by the method that calls it. Parameters are enclosed in parentheses after the method name in the method declaration, and types must be specified for parameters.

This method requires two parameters. A String parameter, which is given the local name name, and a Byte parameter, which is given the local name age. These variables have scope only for the duration of the method and cannot be used after the method returns.

Parameters can be passed in two ways: by value or by reference. In the .NET Framework, parameters are passed by value by default. This means that whenever a parameter is supplied, a copy of the data contained in the variable is made and passed to the method.

Any changes made in the value passed to the method are not reflected in the original variable. Although it is the default setting, you can explicitly indicate that a variable be passed by value in Visual Basic with the ByVal keyword.

When parameters are passed by reference, on the other hand, a reference to the memory location where the variable resides is supplied instead of an actual value. Thus, every time the method performs a manipulation on that variable, the changes are reflected in the actual object. To pass a parameter by reference in Visual Basic .NET, you use the keyword ByRef. In Visual C#, the keyword ref is used.

If your parameter is a reference type, it makes no difference if the parameter is passed by value or by reference—the behavior will be the same. In both cases, any manipulations done on the parameter will be reflected in the object passed as a parameter.

Output Parameters:

In Visual C#, you can also use output parameters. This feature is not available in Visual Basic .NET. An output parameter is a parameter that is passed from a called method to the method that called it—that is, the reverse direction.

Output parameters are useful if you want a method to return more than a single value. An output parameter is specified by using the out keyword. Output parameters are always passed by reference and do not need to be initialized before use.

Optional Parameters:

In Visual Basic .NET, you are able to specify optional parameters for your methods. This feature is not available in Visual C#. You specify a parameter as optional using the Optional keyword. Optional parameters must be the last parameters in a method declaration, and you must supply default values for optional parameters.

Constructors and Destructors:

The constructor is the first method that is run when an instance of a type is created. In Visual Basic, the constructor is always Sub New. In Visual C#, it is a method with the same name as the class. You use a constructor to initialize class and structure data before use. Constructors can never return a value, and can be overridden to provide custom intitialization functionality . A constructor can also contain calls to other methods.

Similarly, a destructor is the last method run by a class. A destructor (known as a finalizer in Visual Basic) contains code to "clean up" when a class is destroyed. This might include decrementing counters or releasing resources. A finalizer in Visual Basic .NET is always Sub Finalize(), and a destructor in Visual C# is a method with the same name as the class preceded by a tilde (~).

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DAY 1 MICROSOFT DOT NET FRAME WORK

DAY 2 MICROSOFT DOT NET BASE CLASS LIBRARY

DAY 3 MICROSOFT DOT NET CLASSES AND STRECTURES

DAY 4 METHODS IN FRAME WORK

DAY 5 INPUT VALIDATIONS IN DOT NET PART ONE

DAY 6 INPUT VALIDATIONS IN DOT NET PART TWO

DAY 7 DATA TYPES IN DOT NET

DAY 8 DATA TYPES IN DOT NET PART TWO

DAY 9 IMPLEMENTING PROPERTIES IN DOT NET

DAY 10 DELEGATES AND EVENTS