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

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"

Reading a file line by line is useful when handling large files without loading everything into memory at once.

✅ Best Practice: Use File.ReadLines() which is more memory efficient.

Example

foreach (string line in File.ReadLines("file.txt"))
{
    Console.WriteLine(line);
}

Why use ReadLines()?

Reads one line at a time, reducing overall memory usage. Ideal for large files (e.g., logs, CSVs).

Alternative: Use StreamReader (More Control)

For scenarios where you need custom processing while reading the contents of the file:

using (StreamReader reader = new StreamReader("file.txt"))
{
    string? line;
    while ((line = reader.ReadLine()) != null)
    {
        Console.WriteLine(line);
    }
}

Why use StreamReader?

Lets you handle exceptions, encoding, and buffering. Supports custom processing (e.g., search for a keyword while reading).

When to Use ReadAllLines()? If you need all lines at once, use:

string[] lines = File.ReadAllLines("file.txt");

Caution: Loads the entire file into memory—avoid for large files!

Using SqlDataReader asynchronously prevents blocking the main thread, improving performance in web apps and large queries. Here’s how to do it properly.

Use await with ExecuteReaderAsync()

using (SqlConnection conn = new SqlConnection(connectionString))
{
    await conn.OpenAsync();
    using (SqlCommand cmd = new SqlCommand("SELECT * FROM Users", conn))
    using (SqlDataReader reader = await cmd.ExecuteReaderAsync()) 
    {
        while (await reader.ReadAsync()) 
        {
            Console.WriteLine(reader["Username"]);
        }
    } // ✅ Auto-closes reader
} // ✅ Auto-closes connection

Why use async?

A couple of reasons:

• Frees up the thread while waiting for the database.
• Improves scalability in ASP.NET Core and web apps.

⚡ Alternative: ConfigureAwait(false) for ASP.NET

Use ConfigureAwait(false) in library code to avoid deadlocks in UI frameworks like ASP.NET.

using (SqlConnection conn = new SqlConnection(connectionString))
{
    await conn.OpenAsync().ConfigureAwait(false);
    using (SqlCommand cmd = new SqlCommand("SELECT * FROM Users", conn))
    using (SqlDataReader reader = await cmd.ExecuteReaderAsync().ConfigureAwait(false)) 
    {
        while (await reader.ReadAsync().ConfigureAwait(false)) 
        {
            Console.WriteLine(reader["Username"]);
        }
    }
}