String Interpolation in C#: A Cleaner Way to Format Strings

Primary constructors, introduced in C# 12, offer a more concise way to define class parameters and initialize fields.

This feature reduces boilerplate code and makes classes more readable.

Traditional Approach vs Primary Constructor

Before primary constructors, you would likely write something like the following:

public class UserService
{
    private readonly ILogger _logger;
    private readonly IUserRepository _repository;

    public UserService(ILogger logger, IUserRepository repository)
    {
        _logger = logger;
        _repository = repository;
    }

    public async Task<User> GetUserById(int id)
    {
        _logger.LogInformation("Fetching user {Id}", id);
        return await _repository.GetByIdAsync(id);
    }
}

With primary constructors, this becomes:

public class UserService(ILogger logger, IUserRepository repository)
{
    public async Task<User> GetUserById(int id)
    {
        logger.LogInformation("Fetching user {Id}", id);
        return await repository.GetByIdAsync(id);
    }
}

Key Benefits

1. Reduced Boilerplate: No need to declare private fields and write constructor assignments
2. Parameters Available Throughout: Constructor parameters are accessible in all instance methods
3. Immutability by Default: Parameters are effectively readonly without explicit declaration

Real-World Example

Here's a practical example using primary constructors with dependency injection:

public class OrderProcessor(
    IOrderRepository orderRepo,
    IPaymentService paymentService,
    ILogger<OrderProcessor> logger)
{
    public async Task<OrderResult> ProcessOrder(Order order)
    {
        try
        {
            logger.LogInformation("Processing order {OrderId}", order.Id);
            
            var paymentResult = await paymentService.ProcessPayment(order.Payment);
            if (!paymentResult.Success)
            {
                return new OrderResult(false, "Payment failed");
            }

            await orderRepo.SaveOrder(order);
            return new OrderResult(true, "Order processed successfully");
        }
        catch (Exception ex)
        {
            logger.LogError(ex, "Failed to process order {OrderId}", order.Id);
            throw;
        }
    }
}

Tips and Best Practices

1. Use primary constructors when the class primarily needs dependencies for its methods
2. Combine with records for immutable data types:

public record Customer(string Name, string Email)
{
    public string FormattedEmail => $"{Name} <{Email}>";
}

3. Consider traditional constructors for complex initialization logic

Primary constructors provide a cleaner, more maintainable way to write C# classes, especially when working with dependency injection and simple data objects.

Understanding the difference between COUNT() and COUNT(DISTINCT) in SQL is crucial for accurate data analysis.

COUNT() returns the total number of rows that match your query criteria, including duplicates, while COUNT(DISTINCT) returns the number of unique values in a specified column, effectively eliminating duplicates from the count.

For example, if you have a table of customer orders where a single customer can place multiple orders, COUNT(customer_id) would give you the total number of orders, whereas COUNT(DISTINCT customer_id) would tell you how many unique customers have placed orders.

The choice between these functions depends on your specific reporting needs. Use COUNT() when you need the total number of records, such as counting all sales transactions or total number of website visits.

Use COUNT(DISTINCT) when you need to know unique occurrences, like the number of different products sold or unique visitors to your website. It's also worth noting that COUNT(*) counts all rows including NULL values, while COUNT(column_name) excludes NULL values from that specific column, which can lead to different results depending on your data structure.

Example

-- Example table: customer_orders
-- customer_id | order_date  | product_id
-- 1          | 2024-01-01  | 100
-- 1          | 2024-01-02  | 101
-- 2          | 2024-01-01  | 100
-- 3          | 2024-01-03  | 102

-- Count all orders
SELECT COUNT(*) as total_orders
FROM customer_orders;
-- Result: 4 (counts all rows)

-- Count unique customers who placed orders
SELECT COUNT(DISTINCT customer_id) as unique_customers
FROM customer_orders;
-- Result: 3 (counts unique customer_ids: 1, 2, 3)

-- Count unique products ordered
SELECT COUNT(DISTINCT product_id) as unique_products
FROM customer_orders;
-- Result: 3 (counts unique product_ids: 100, 101, 102)

-- Compare regular COUNT with COUNT DISTINCT
SELECT 
    COUNT(customer_id) as total_orders,
    COUNT(DISTINCT customer_id) as unique_customers
FROM customer_orders;
-- Result: total_orders = 4, unique_customers = 3

In C#, you can format an integer with commas (thousands separator) using ToString with a format specifier.

int number = 1234567;
string formattedNumber = number.ToString("N0"); // "1,234,567"
Console.WriteLine(formattedNumber);

Explanation:

"N0": The "N" format specifier stands for Number, and "0" means no decimal places. The output depends on the culture settings, so in regions where , is the decimal separator, you might get 1.234.567.

Alternative:

You can also specify culture explicitly if you need a specific format:

using System.Globalization;

int number = 1234567;
string formattedNumber = number.ToString("N0", CultureInfo.InvariantCulture);
Console.WriteLine(formattedNumber); // "1,234,567"