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==A nested if statement==

<source lang="csharp">class MainClass
{
public static void Main()
{
int intValue = 1500;
string stringValue = " ";
if (intValue < 1000)
{
System.Console.WriteLine("intValue < 1000");
}
else
{
System.Console.WriteLine("intValue >= 1000");
if (stringValue == "closed")
{
System.Console.WriteLine("closed");
}
}
}
}</source>
<pre class=codeResult>intValue >= 1000</pre>

==bool values in if statement==

<source lang="csharp">using System;

class Example {
public static void Main() {
bool b;

b = false;
Console.WriteLine("b is " + b);
b = true;
Console.WriteLine("b is " + b);

// a bool value can control the if statement
if(b)
Console.WriteLine("This is executed.");

b = false;
if(b)
Console.WriteLine("This is not executed.");

}
}</source>
<pre class=codeResult>b is False
b is True
This is executed.</pre>

==Demonstrate the if statement==

<source lang="csharp">using System;

class MainClass {
public static void Main() {
int a, b, c;

a = 2;
b = 3;

if(a < b)
Console.WriteLine("a is less than b");

if(a == b)
Console.WriteLine("you won"t see this");

Console.WriteLine();

c = a - b;

Console.WriteLine("c is",c);
if(c >= 0)
Console.WriteLine("c is non-negative");
if(c < 0)
Console.WriteLine("c is negative");

Console.WriteLine();

c = b - a;
Console.WriteLine("c is",c);
if(c >= 0)
Console.WriteLine("c is non-negative");
if(c < 0)
Console.WriteLine("c is negative");
}
}</source>
<pre class=codeResult>a is less than b
c is
c is negative
c is
c is non-negative</pre>

==Determine if a value is positive, negative, or zero==

<source lang="csharp">using System;

class MainClass {
public static void Main() {
int i;

for(i=-5; i <= 5; i++) {

Console.Write("Testing " + i + ": ");

if(i < 0)
Console.WriteLine("negative");
else if(i == 0)
Console.WriteLine("no sign");
else
Console.WriteLine("positive");
}
}
}</source>
<pre class=codeResult>Testing -5: negative
Testing -4: negative
Testing -3: negative
Testing -2: negative
Testing -1: negative
Testing 0: no sign
Testing 1: positive
Testing 2: positive
Testing 3: positive
Testing 4: positive
Testing 5: positive</pre>

==If a value is positive or negative==

The semicolon signals the end of a statement.

<source lang="csharp">using System;

class MainClass {
public static void Main() {
int i;

for(i=-5; i <= 5; i++) {
Console.Write("Testing " + i + ": ");

if(i < 0)
Console.WriteLine("negative");
else
Console.WriteLine("positive");
}
}
}</source>
<pre class=codeResult>Testing -5: negative
Testing -4: negative
Testing -3: negative
Testing -2: negative
Testing -1: negative
Testing 0: positive
Testing 1: positive
Testing 2: positive
Testing 3: positive
Testing 4: positive
Testing 5: positive</pre>

==if statement with || and &&==

<source lang="csharp">using System;
class MainClass
{
static void Main(string[] args)
{
int a = 5, b = 5, c = 10;
if (a == b)
Console.WriteLine(a);
if ((a > c) || (a == b))
Console.WriteLine(b);
if ((a >= c) && (b <= c))
Console.WriteLine(c);
}
}</source>
<pre class=codeResult>5
5</pre>

==Relational operators that can be used in a conditional expression.==

Operator
Meaning
<
Less than
<=
Less than or equal
>
Greater than
>=
Greater than or equal
==
Equal to
!=
Not equal

==The if Statement==

You can selectively execute part of a program through the if statement.
Its simplest form is shown here:

<source lang="csharp">if(condition)
statement;</source>

==Use an if statement that executes a block==

A code block is a grouping of two or more statements.
This is done by enclosing the statements between opening and closing curly braces.

<source lang="csharp">class MainClass
{
public static void Main()
{
int smallNumber = 5;
int bigNumber = 100;
if (bigNumber < smallNumber)
{
System.Console.Write(bigNumber);
System.Console.Write(" is less than ");
System.Console.Write(smallNumber);
}
else
{
System.Console.Write(smallNumber);
System.Console.Write(" is less than ");
System.Console.Write(bigNumber);
}
}
}</source>
<pre class=codeResult>5 is less than 100</pre>

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