How to Read a File Line by Line in C#?

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"]);
        }
    }
}

Storing passwords as plain text is dangerous. Instead, you should hash them using a strong, slow hashing algorithm like BCrypt, which includes built-in salting and resistance to brute-force attacks.

Step 1: Install BCrypt NuGet Package

Before using BCrypt, install the BCrypt.Net-Next package:

dotnet add package BCrypt.Net-Next

or via NuGet Package Manager:

Install-Package BCrypt.Net-Next

Step 2: Hash a Password

Use BCrypt.HashPassword() to securely hash a password before storing it:

using BCrypt.Net;

string password = "mySecurePassword123";
string hashedPassword = BCrypt.HashPassword(password);

Console.WriteLine(hashedPassword); // Output: $2a$12$...

Step 3: Verify a Password

To check a user's login attempt, use BCrypt.Verify():

bool isMatch = BCrypt.Verify("mySecurePassword123", hashedPassword);
Console.WriteLine(isMatch); // Output: True

Ensuring proper hashing should be at the top of your list when it comes to building authentication systems.

When working with SQL Server, you may often need to count the number of unique values in a specific column. This is useful for analyzing data, detecting duplicates, and understanding dataset distributions.

Using COUNT(DISTINCT column_name)

To count the number of unique values in a column, SQL Server provides the COUNT(DISTINCT column_name) function. Here’s a simple example:

SELECT COUNT(DISTINCT column_name) AS distinct_count
FROM table_name;

This query will return the number of unique values in column_name.

Counting Distinct Values Across Multiple Columns

If you need to count distinct combinations of multiple columns, you can use a subquery:

SELECT COUNT(*) AS distinct_count
FROM (SELECT DISTINCT column1, column2 FROM table_name) AS subquery;

This approach ensures that only unique pairs of column1 and column2 are counted.

Why Use COUNT DISTINCT?

• Helps in identifying unique entries in a dataset.
• Useful for reporting and analytics.
• Efficient way to check for duplicates.

By leveraging COUNT(DISTINCT column_name), you can efficiently analyze your database and extract meaningful insights. Happy querying!