How to Resolve Error "CS0442: Abstract properties cannot have private accessors" in C#

The Compiler Error CS0442 is an access modifier conflict error. The message reads: "Property': abstract properties cannot have private accessors".

In C#, the abstract keyword on a property implies a contract: "I am not providing an implementation here; the derived class MUST provide the implementation."

However, the private keyword means: "This member is only visible inside this specific class; derived classes cannot see or touch it."

These two concepts contradict each other. If a property accessor (like set) is private, the derived class cannot see it. If the derived class cannot see it, it cannot override it to provide the required implementation. Therefore, the compiler forbids abstract properties from having private accessors.

Understanding the Conflict

To implement an abstract property in a child class, you must use the override keyword.

• Abstract Requirement: "Child class, you must implement the set logic."
• Private Restriction: "Child class, you are not allowed to know the set exists."

The compiler detects this deadlock immediately. You are requiring a child class to implement something you are simultaneously hiding from it.

Scenario: The Impossible Override

This error commonly occurs when designing a base class where you want a public getter but want to restrict setting values to the class hierarchy, and you accidentally choose private instead of protected.

Example of error:

public abstract class BankAccount
{
    // ⛔️ Error CS0442: 'BankAccount.Balance': abstract properties 
    // cannot have private accessors.
    // The compiler knows that no class inheriting from BankAccount 
    // will be able to override this specific 'set' accessor.
    public abstract decimal Balance { get; private set; }
}

Solution 1: Use protected Instead

If your intention is to prevent the "outside world" (public consumers) from setting the property, but you want derived classes to handle the implementation, use protected.

protected allows derived classes to see and override the accessor, while keeping it hidden from the public API.

Solution:

public abstract class BankAccount
{
    // ✅ Correct: 'protected' allows the derived class to implement the setter.
    public abstract decimal Balance { get; protected set; }
}

public class SavingsAccount : BankAccount
{
    private decimal _balance;

    public override decimal Balance 
    { 
        get { return _balance; }
        // We can override it because it is protected (visible to us)
        protected set { _balance = value; } 
    }
}

Solution 2: Make the Property Non-Abstract

If the base class actually knows how to store the value, and you simply want to prevent external modification, you do not need to make the property abstract. You can define it as a standard property in the base class with a private setter.

In this scenario, the base class holds the storage, and derived classes simply inherit the behavior without needing to override it.

Solution:

public abstract class BankAccount
{
    // ✅ Correct: Not abstract. The base class handles storage.
    // Derived classes can read Balance, but only BankAccount can write to it directly.
    public decimal Balance { get; private set; }

    protected void Deposit(decimal amount)
    {
        // Internal logic in the base class updates the private setter
        Balance += amount;
    }
}

note

Access logic: In this solution, SavingsAccount cannot say this.Balance = 50. It must call a method like Deposit provided by the base class, because the setter remains strictly private to BankAccount.

Conclusion

CS0442 protects you from creating an impossible contract.

1. Check the Goal: Do you want the child class to define how the setting happens?
   • Yes: Use abstract with protected set.
2. Check the Goal: Do you want the base class to handle storage, but keep it read-only for others?
   • Yes: Remove abstract and use a standard property with private set.