Interface — IRepository pattern — C# Programming

Problem

Define IRepository with GetById and implement in-memory repo.

Hints

Add GetById to interface and implement in class

Your practice code

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Solution

using System;
using System.Collections.Generic;

interface IRepository {
    string GetById(int id);
}
class InMemoryRepo : IRepository {
    private readonly Dictionary<int, string> _data = new() { [1] = "Item1" };
    public string GetById(int id) => _data.TryGetValue(id, out var v) ? v : null;
}
class Program {
    static void Main() {
        IRepository repo = new InMemoryRepo();
        Console.WriteLine(repo.GetById(1));
    }
}

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Explanation

Program to interface, not implementation—SOLID dependency inversion in .NET interviews.