10. Properties in C#

Level: Beginner

ℹ️ What You'll Learn

• What a property is
• Why properties are better than public fields
• Use get and set
• Create auto-properties
• Use private setters for safer data
• Add simple validation in a property
• Use properties in the School Management System

In the previous article, you learned classes and objects.

Now we learn how a class stores data safely.

In C#, a property is the normal way to read and write data inside a class.

The Problem: Public Fields Can Be Changed Wrongly

Imagine this class:

public class Student
{
    public string Name;
    public int Percentage;
}

This looks easy, but it is unsafe.

Student student = new Student();
student.Name = "";
student.Percentage = -50;

Problem:

Name should not be empty.
Percentage should not be negative.
But public fields allow both mistakes.

Properties help us control this.

Quick Definitions

• Field - Variable inside a class
• Property - Controlled way to read or write class data
• get - Reads the value
• set - Changes the value
• Auto-property - Short property syntax used for simple data
• Private setter - Allows reading from outside, but changing only inside the class
• Validation - Checking data before saving it

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Step 1: Auto-Properties

Auto-properties are the simplest properties.

public class Student
{
    public string Name { get; set; } = "";
    public int RollNumber { get; set; }
    public double Percentage { get; set; }
}

Use them like this:

Student student = new Student();
student.Name = "Sahasra Kumar";
student.RollNumber = 101;
student.Percentage = 84.8;

Meaning:

Code	Meaning
get	Other code can read the value
set	Other code can change the value
= ""	Starting value for text

Step 2: Read-Only from Outside

Sometimes outside code should read a value, but not change it directly.

Example: roll number should be set only when creating the student.

public class Student
{
    public string Name { get; set; } = "";
    public int RollNumber { get; private set; }

    public Student(int rollNumber)
    {
        RollNumber = rollNumber;
    }
}

Usage:

Student student = new Student(101);
student.Name = "Priya";

Console.WriteLine(student.RollNumber);

This is not allowed:

student.RollNumber = 999; // Error: setter is private

Step 3: Property with Validation

Use a full property when you need to check the value.

public class Student
{
    private double _percentage;

    public double Percentage
    {
        get { return _percentage; }
        set
        {
            if (value < 0 || value > 100)
            {
                Console.WriteLine("Percentage must be between 0 and 100.");
                return;
            }

            _percentage = value;
        }
    }
}

Here:

_percentage stores the real value.
Percentage controls access to that value.

Full Example: Student Properties

💻 Try It — Console App

💡 Paste into Program.cs and press F5⌥ GitHub

public class Student
{
    private double _percentage;

    public string Name { get; set; } = "";
    public int RollNumber { get; private set; }

    public double Percentage
    {
        get { return _percentage; }
        set
        {
            if (value < 0 || value > 100)
            {
                Console.WriteLine("Invalid percentage.");
                return;
            }

            _percentage = value;
        }
    }

    public Student(int rollNumber)
    {
        RollNumber = rollNumber;
    }

    public void PrintInfo()
    {
        Console.WriteLine($"Name: {Name}");
        Console.WriteLine($"Roll Number: {RollNumber}");
        Console.WriteLine($"Percentage: {Percentage}");
    }
}

Student student = new Student(101);
student.Name = "Sahasra Kumar";
student.Percentage = 84.8;
student.PrintInfo();

student.Percentage = -20;

Expected output:

Name: Sahasra Kumar
Roll Number: 101
Percentage: 84.8
Invalid percentage.

When You'll Use This in SMS

Properties are used in almost every School Management class.

Student:

• Name
• RollNumber
• ClassName
• Percentage

FeeAccount:

• TotalFees
• PaidAmount
• Balance

Teacher:

• Name
• EmployeeId
• Subject
• Salary

Real rule:

Use properties for class data.
Use validation when wrong data can damage the system.

Try This Now

Run the full example. Then experiment:

1. Change percentage to 95
2. Change percentage to 120
3. Try to change RollNumber after creating the object
4. Add a new property called ClassName

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ℹ️ Video Tutorial

C# properties video coming soon on NexCoding YouTube. Subscribe for updates.

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Common Mistakes

Mistake 1: Using public fields everywhere

Public fields give no control. Prefer properties.

Mistake 2: Forgetting starting values for strings

Use = "" for beginner examples to avoid null confusion.

Mistake 3: Using validation for every property

Use validation only when the value needs rules.

Practice Task

Create a Teacher class with:

• Name
• EmployeeId with private setter
• Subject
• ExperienceYears with validation: cannot be negative

Create one teacher object and print the details.

Quick Revision

Question	Answer
What is a property?	Controlled way to read/write class data
What does get do?	Reads a value
What does set do?	Changes a value
What is an auto-property?	Short property syntax
Why use private set?	To stop outside code from changing the value

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🎯 Q1: What is a property in C#?

A property is a controlled way to read and write data inside a class.

🎯 Q2: What is the difference between field and property?

A field is direct storage. A property can control access and add validation.

🎯 Q3: What does private set mean?

private set means outside code can read the value, but only the class can change it.

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🤖Use AI to Learn Faster

⚠️ Important for beginners: Do NOT use AI to write your code yet. Type every example yourself. Your brain learns by doing, not by reading AI output. Use AI only to explain and quiz you — not to code for you. Once you have strong fundamentals, AI becomes a powerful productivity tool for repetitive tasks.

Use ChatGPT, Claude, or Copilot to go deeper on C# properties. Try these prompts:

• "Explain C# properties like I am a beginner"
• "Give me 5 practice tasks for get and set"
• "Explain property validation using school examples"
• "Quiz me with 5 questions about C# properties"

💡 Tip: After reading this article, paste your own code into AI and ask "What could go wrong here and why?" — fastest way to find edge cases and deepen understanding.

Next Article

Encapsulation and Access Modifiers ->