Bits of .NET

🔌 Extension Methods = Add Functionality

Can’t modify existing types? Extension methods add functionality. Use like instance methods.

📝 Extension Examples

// Static class, static methods
public static class StringExtensions
{
    public static string ToTitleCase(this string input)
    {
        if (string.IsNullOrEmpty(input)) return input;
        return char.ToUpper(input[0]) + input.Substring(1).ToLower();
    }
    
    public static bool IsValidEmail(this string email)
    {
        try {
            var addr = new System.Net.Mail.MailAddress(email);
            return addr.Address == email;
        } catch {
            return false;
        }
    }
    
    public static string Truncate(this string value, int maxLength)
    {
        return value?.Length > maxLength ? value.Substring(0, maxLength) + "..." : value;
    }
}

// Usage
string name = "john doe";
name = name.ToTitleCase();  // "John Doe"

string email = "user@example.com";
bool valid = email.IsValidEmail();  // true

// DateTime extensions
public static class DateTimeExtensions
{
    public static bool IsWeekend(this DateTime date)
    {
        return date.DayOfWeek == DayOfWeek.Saturday || date.DayOfWeek == DayOfWeek.Sunday;
    }
    
    public static DateTime StartOfWeek(this DateTime date)
    {
        var diff = (7 + (date.DayOfWeek - DayOfWeek.Monday)) % 7;
        return date.AddDays(-diff).Date;
    }
}

// IEnumerable extensions
public static class EnumerableExtensions
{
    public static IEnumerable ForEach(this IEnumerable source, Action action)
    {
        foreach (var item in source)
        {
            action(item);
            yield return item;
        }
    }
}

// Extension Method Tips
- Put in dedicated namespace
- Use meaningful method names
- Keep extensions focused
- Don't override existing methods
- Use with LINQ for readability

💡 Extension Tips

• Put in dedicated namespace
• Use meaningful method names
• Keep extensions focused
• Don’t override existing methods
• Use with LINQ for readability