Wei-Meng Lee - C# 2008 Programmer's Reference

///

/// The entry point for the program

///

///

static void Main(string[] args) {

Console.Write("Hello, ");

for (int i = 0; i < args.Length; i++)

Console.Write("{0} ", args[i]);

Console.Write("! This is my first C# program!");

Console.ReadLine();

return;

}

///

/// Adds two numbers and returns the result

///

/// Number 1

/// Number 2

/// Sum of Number 1 and 2

private int AddNumbers(int num1, int num2) {

//---implementations here---

}

}

}

To enable generation of the XML document containing the XML comments, right-click the project name in Solution Explorer and select Properties.

You can also generate the XML documentation file using the csc.execompiler at the command prompt using the /docoption:

csc Program.cs /doc:HelloWorld.xml

In the Build tab, tick the XML Documentation File checkbox and use the default path suggested: bin\Debug\HelloWorld.XML(see Figure 3-7).

Figure 3-7

Build the project by right-clicking the project name in Solution Explorer and selecting Build.

You will now find the HelloWorld.xmlfile (see Figure 3-8) located in the bin\Debug\ folder of the project.

Figure 3-8

You can now convert this XML file into a MSDN-style documentation file. Appendix C shows you how to use the SandCastle tool to do this.

C# is a strongly typed language and as such all variables and objects must have a declared data type. The data type can be one of the following:

□ Value

□ Reference

□ User-defined

□ Anonymous

You'll find more information about user-defined types in Chapter 4 and about anonymous types in Chapter 14.

A value type variable contains the data that it is assigned. For example, when you declare an int (integer) variable and assign a value to it, the variable directly contains that value. And when you assign a value type variable to another, you make a copy of it. The following example makes this clear:

class Program {

static void Main(string[] args) {

int num1, num2;

num1 = 5;

num2 = num1;

Console.WriteLine("num1 is {0}. num2 is {1}", num1, num2);

num2 = 3;

Console.WriteLine("num1 is {0}. num2 is {1}", num1, num2);

Console.ReadLine();

return;

}

}

The output of this program is:

num1 is 5. num2 is 5

num1 is 5. num2 is 3

As you can observe, num2is initially assigned a value of num1(which is 5). When num2is later modified to become 3, the value of num1remains unchanged (it is still 5). This proves that the num1and num2each contains a copy of its own value.

Following is another example of value type. Point is a structure that represents an ordered pair of integer x and y coordinates that defines a point in a two-dimensional plane (structure is another example of value types). The Pointclass is found in the System.Drawingnamespace and hence to test the following statements you need to import the System.Drawingnamespace.

Chapter 4 discusses structures in more detail.

Point pointA, pointB;

pointA = new Point(3, 4);

pointB = pointA;

Console.WriteLine("point A is {0}. pointB is {1}",

pointA.ToString(), pointB.ToString());

pointB.X = 5;

pointB.Y = 6;

Console.WriteLine("point A is {0}. pointB is {1}",

pointA.ToString(), pointB.ToString());

These statements yield the following output:

point A is {X=3,Y=4}. pointB is {X=3,Y=4}

point A is {X=3,Y=4}. pointB is {X=5,Y=6}

As in the earlier example, changing the value of the pointB does not change the value of pointA.

The .NET Framework ships with a set of predefined C# and .NET value types. These are described in the following table.

To declare a variable of a predefined type, you can either use the C# type or the .NET Framework type. For example, to declare an integer variable, you can either use the int or System.Int32type, as shown here:

int num1 = 5;

//---or---

System.Int32 num2 = 5;

To get the type of a variable, use the GetType()method:

Console.WriteLine(num1.GetType()); //---System.Int32---

To get the .NET equivalent of a C# type, use the typeof()method. For example, to learn the .NET type equivalent of C#'s float type, you can use the following statements:

Type t = typeof(float);

Console.WriteLine(t.ToString()); //---System.Single---