Understanding Control Structures in C#
Programming requires solving complex problems using code, to be able to solve these problems you need to learn the basic building blocks for writing a good program. These building blocks will assist one in making various decisions in the program. <!--more--> One example could be wanting to obtain a positive result while disregarding the negative one. Another may be that one wishes for the program to re-run a certain section of the code, necessitating the use of control structures.
This knowledge will assist you as a programmer in choosing a specific path or direction. In this article you will understand how to work with control structures in C# using various examples.
Table of contents
Prerequisites
To follow along with this tutorial, the reader will need the following:
- A basic knowledge of C & C++ programming language.
- A code editor installed on your computer
Selection statements
First, of all, we need a recall of the definition of a statement. In programming, statements can be instructions that are initiated by the user.
For instance:
console.writeline("this is my statement");
In this sub-topic, we are going to look at; if, else, else if, and switch statements.
If statements
It has a specification to execute only a true statement.
Syntax
if(condition)
{
statement;// it must be true
}
An example written in form of a program.
using System;
namespace MyApplication
{
class demo
{
static void Main(string[] args)
{
if (90> 9) // note that 'if' should be in lowercase otherwise it will bring an error
{
Console.WriteLine("yes i agree 90 is greater");//what will be displayed
}
}
}
}
The above program has been executed since the condition given is true (90>9) otherwise it won't execute.
Else statement
This statement is opposite to that of the 'if' above. It executes if the condition is false. The compiler has to go through the if first to check whether it meets the condition. If it does not then we come to the else statement (the compiler evaluate line by line).
Syntax
if(condition)
{
statement;//executes if conditiom is true
}
else
{
statement;// executes if conditiom is false
}
An example
using System;
namespace MyApplication
{
class demo
{
static void Main(string[] args)
{
if (9>90)
// note that it should be in lowercase otherwise it will bring an error
{
Console.WriteLine("yes i agree 90 is greater");
// this will not be excuted
}
else
{
Console.WriteLine("yes 9 is not greater 90");
//this is what will be displayed.
}
}
}
}
From the code above, if the first statement doesn't meet the condition, the compiler will proceed to the next, which is the 'else statement', and execute it.
Else if statement
For this statement to execute, the other above conditions in that program (if condition) should be false.
Syntax
if(condition1)
{
statement;
}
else if(condition2)
{
statement;
}
else(condition3)
// this is executed when condition 1 and 2 are both false
{
statement;
}
An example
using System;
namespace MyApplication
{
class demo
{
static void Main(string[] args)
{
int age = 18;
if (age < 10)
{
Console.WriteLine("still child.");
// do not meet condition
}
else if (age < 15)
{
Console.WriteLine("adolescence stage.");
//do not meet condition
}
else
{
Console.WriteLine("you are a man.");
// meets condition
}
}
}
}
Code output:
you are man
In the program above, the compiler will not execute the first and the second statement since they don't meet conditions. Therefore the third statement will be executed.
Switch statements
Here the execution is done when the expression matches with the values in the case. The keyword break helps save time for execution since the compiler breaks for the next case (expression).
Syntax
switch(expression)
{
case: 1
statement;
break;
case: 2
statement;
break;
.
.
.
case: n
statement;
break;
}
An example
using System;
namespace MyApplication
{
class demo
{
static void Main(string[] args)
{
int year = 2;
switch (year)
{
case 1:
Console.WriteLine("2021");
break;
case 2:
Console.WriteLine("2022");
//it will output this we have switched it.
break;
case 3:
Console.WriteLine("2023");
break;
case 4:
Console.WriteLine("2024");
break;
}
}
}
Code output:
2022
Iteration statements
Iteration means to repeat something several times. Similarly, programming iteration is when you find an algorithm that repeats itself several times until it achieves or meets specific conditions. Iteration statements are as known as loops.
While statements
Programmers find it easy to learn and understand while statements. Here, it keeps iterating as long as the statement meets the condition (true condition).
Syntax
while(condition)
statement;
An example
using System;
namespace MyApplication
{
class demo
{
static void Main(string[] args)
{
int j = 10;
// we assign a value
while (j <20 )
// then the condition
{
Console.WriteLine(j);
j++;
//incrementing
}
}
}
}
The code above will execute numbers from 10 to 19 since the condition says to output j when j<20 and we already know our j is equal to 10.
Do while
Do while is unlike other while loop where we first look at the condition. Do while will first do/execute the statement before it looks whether the statement is true and thereafter it checks if it is true to repeat the loop.
Syntax
do
{
statement;
}
while (condition)
An example
using System;
namespace MyApplication
{
class demo
{
static void Main(string[] args)
{
int j = 10;
do
{
Console.WriteLine(j);
//we output before checking the condition
j++;
} while(j<20);
}
}
}
For loop
The good thing about a "for loop" is that one can easily know how many times the system will iterate or at what point will it stop and give feedback.
Syntax
for(initialization;condition; increment/decrement)
{
statement;
}
An example
using System;
namespace MyApplication
{
class demo
{
static void Main(string[] args)
{
int j = 10;
for (j=10; j<15;j++)//the loop
{
Console.WriteLine(j);
}
}
}
}
We have first initialized our 'j' to be equal to 10, then the condition is that 'j' can be valued between 9 and 15 since 10 is already involved, so it will output values from 10 to 14.
Jump statements
As the name suggests jump statements will transfer control from one place to another as per the condition. In this sub, the topic will learn some of the jump statements.
Break statement
The break statement is used when one needs the code to terminate some statement and perhaps go to the next. Like in switch statements it is used to terminate one statement and go to the next one or terminate the whole program.
An example
using System;
class demo
{
static public void Main()
{
for (int j = 0; j < 5; j++)
{
if (j == 4)
// it will break when it reaches here
break;
Console.WriteLine("hello");
}
}
}
Code output:
hello
hello
hello
hello
The code output above will display 'hello,' four times since the condition says it should break out of the loop when it reaches 4th time.
Go to statements
This is a statement that once encountered jumps to the specified location. Below we are going to learn (through an example) how to implement the goto statement.
using System;
namespace demo
{
class Program
{
static void Main(string[] args)
{
int j;
for (j=5; j<15;j++)
{
if(j ==10 )
{
goto endloop;//it will end the program once it gets that j is equal to ten
}
Console.WriteLine("j value: {0}", j);//outputing j
}
endloop: Console.WriteLine("Thank you for your time");
Console.ReadLine();
}
}
}
Code output:
j value: 5
j value:6
j value:7
j value:8
j value:9
Thank you for your time
The program above will display 5 to 9 since 'j' we already initiated it and gave it 5. Therefore the compiler will jump up to 10 since our goto statement directs to 10.
Continue statement
These kinds of statements are mostly used when a programmer wants the program to skip a certain part of an execution, for example in loop statements. Here once the compiler meets the continue statement, it jumps to begin the loop again as per the condition statement.
An example
using System;
class demo{
public static void Main()// Main Method
{
for (int j = 1; j <= 7; j++)
{
if (j == 3) // once the compiler reaches 3,it will skip it and continue with the next number after 3 which is 4
continue;
Console.WriteLine(j); // j is values from 1 to 7 , when 3 is excluded
}
}
}
Return statement
Usually, the return statement in C# is used to stop the execution of the method where it appears and return control to the calling function.
For example:
using System;
class demo {
static int sub(int b)
{
int sub = b - b;
// the return statement
return sub;
}
// Main Method
static public void Main()
{
int number = 4;
// now calling subtraction function
int result = sub(number);
Console.WriteLine("The answer is {0}", result);
}
}
The program above will return 0 since we have declared the same number 4, therefore our answer will be 0.
Conclusion
In this article, you learned about the control structures in C#. We looked at how to work with selection statements, iteration statements (loops), and the jump statements where in each case you were given examples on how they are implemented.
Happy coding!
Peer Review Contributions by: Jethro Magaji
