Review Materials
Lesson 5-6. Conditional Instruction IF.

Lesson Objective
The goal of the lesson is to present the IF conditional instruction.

Conditional instructions allow for executing specific parts of a program depending on the conditions met. The IF instruction appears in almost every programming language, although its syntax may vary slightly.

This instruction has several variants. In C#, the simplest syntax looks like this:
```csharp
if (logical expression)
{
    //code block that executes if the logical expression is true;
}
```

A more advanced version, assuming the existence of several possible variants:
```csharp
if (condition_1)
{
    //if the condition is met, this piece of code will execute;
}
else if (condition_2)
{
    //executes if condition_1 is not met, but condition_2 is;
}
else // in all other cases, this piece of code will execute
{
    //code block;
}
```
Example 1:
```csharp
int age = Console.Readline();
if (age == 17)
{
    Console.WriteLine("You will reach adulthood this year");
}
```

Example 2:
```csharp
int number1 = 4;
int number2 = 5;

if (number1 > number2)
{
    Console.WriteLine($"{number1} is greater than {number2}");
}
else if (number2 > number1)
{
    Console.WriteLine($"{number2} is greater than {number1}");
}
else
{
    Console.WriteLine("The numbers are equal");
}
Console.WriteLine(number1);
```

Nesting instructions allows for adding conditional instructions inside another instruction.

Example task - A presidential candidate must be at least 35 years old and have collected 100,000 votes. Check if you can run for president.

```csharp
if( are you 35 years old? )
{
    if( Have you collected 100,000 votes? )
    {
        You can run for president!
    }
    else
    {
        You cannot run for president
    }
}
else
{
    You cannot run for president
}
```

Try to convert the above pseudocode into a working program 😉

Watch out for these mistakes!
- Never place a semicolon after the parentheses in if.
```csharp
if(condition);  <- WRONG!
{
}
```

- Remember that a variable declared inside a block is not accessible outside it.
```csharp
if(condition)
{
    int x = 1;
}
x++; <- Error! The variable x is not accessible here!
```

Additional Programmer's Mission:
Create a program that draws 2 numbers from the range of 0 to 100, then check (using the If conditional instruction) if their sum is greater than 50. The program should display a message indicating whether the condition is met or not.

Hint - the draw can be implemented as follows:
```csharp
Random randomMachine = new Random();
int drawnValue = randomMachine.Next(1, 101);
```