Generic extension methods for strings, collections, DateTime, decimals, and entities.
Generic extension methods for common operations.
// Extensions/StringExtensions.cs
public static class StringExtensions
{
/// <summary>
/// Check if string is null, empty, or whitespace
/// </summary>
public static bool IsNullOrEmpty(this string? value)
=> string.IsNullOrWhiteSpace(value);
/// <summary>
/// Check if string has content
/// </summary>
public static bool HasValue(this string? value)
=> !string.IsNullOrWhiteSpace(value);
/// <summary>
/// Truncate string to max length with ellipsis
/// </summary>
public static string Truncate(this string value, int maxLength, string suffix = "...")
{
if (string.IsNullOrEmpty(value) || value.Length <= maxLength)
return value;
return value[..(maxLength - suffix.Length)] + suffix;
}
/// <summary>
/// Convert to title case
/// </summary>
public static string ToTitleCase(this string value)
=> CultureInfo.CurrentCulture.TextInfo.ToTitleCase(value.ToLower());
/// <summary>
/// Format phone number for Thailand
/// </summary>
public static string FormatThaiPhone(this string phone)
{
var digits = new string(phone.Where(char.IsDigit).ToArray());
return digits.Length == 10
? $"{digits[..3]}-{digits[3..6]}-{digits[6..]}"
: phone;
}
}
// Extensions/CollectionExtensions.cs
public static class CollectionExtensions
{
/// <summary>
/// Add or replace item in list
/// </summary>
public static void AddOrReplace<T>(this List<T> list, T item, Func<T, bool> predicate)
{
var index = list.FindIndex(x => predicate(x));
if (index >= 0)
list[index] = item;
else
list.Add(item);
}
/// <summary>
/// Clear and add range
/// </summary>
public static void ClearAndAddRange<T>(this List<T> list, IEnumerable<T> items)
{
list.Clear();
list.AddRange(items);
}
/// <summary>
/// Check if collection is empty
/// </summary>
public static bool IsEmpty<T>(this IEnumerable<T> source)
=> !source.Any();
/// <summary>
/// Check if collection has items
/// </summary>
public static bool HasItems<T>(this IEnumerable<T> source)
=> source.Any();
/// <summary>
/// Safe first or default with predicate
/// </summary>
public static T? SafeFirst<T>(this IEnumerable<T>? source, Func<T, bool>? predicate = null)
{
if (source is null)
return default;
return predicate is null
? source.FirstOrDefault()
: source.FirstOrDefault(predicate);
}
/// <summary>
/// ForEach for IEnumerable
/// </summary>
public static void ForEach<T>(this IEnumerable<T> source, Action<T> action)
{
foreach (var item in source)
action(item);
}
/// <summary>
/// Batch items into chunks
/// </summary>
public static IEnumerable<IEnumerable<T>> Batch<T>(this IEnumerable<T> source, int size)
{
var batch = new List<T>(size);
foreach (var item in source)
{
batch.Add(item);
if (batch.Count == size)
{
yield return batch;
batch = new List<T>(size);
}
}
if (batch.Count > 0)
yield return batch;
}
}
// Extensions/DateTimeExtensions.cs
public static class DateTimeExtensions
{
/// <summary>
/// Get Thailand timezone (UTC+7)
/// </summary>
private static readonly TimeZoneInfo ThailandTimeZone =
TimeZoneInfo.FindSystemTimeZoneById("SE Asia Standard Time");
/// <summary>
/// Convert to Thailand local time
/// </summary>
public static DateTimeOffset ToThailandTime(this DateTimeOffset utc)
=> TimeZoneInfo.ConvertTime(utc, ThailandTimeZone);
/// <summary>
/// Get current Thailand time
/// </summary>
public static DateTimeOffset ThailandNow()
=> TimeZoneInfo.ConvertTime(DateTimeOffset.UtcNow, ThailandTimeZone);
/// <summary>
/// Format for Thai display
/// </summary>
public static string ToThaiDateString(this DateTimeOffset date)
=> date.ToThailandTime().ToString("dd MMM yyyy");
/// <summary>
/// Format with time
/// </summary>
public static string ToThaiDateTimeString(this DateTimeOffset date)
=> date.ToThailandTime().ToString("dd MMM yyyy HH:mm");
/// <summary>
/// Get start of day
/// </summary>
public static DateTimeOffset StartOfDay(this DateTimeOffset date)
=> new(date.Year, date.Month, date.Day, 0, 0, 0, date.Offset);
/// <summary>
/// Get end of day
/// </summary>
public static DateTimeOffset EndOfDay(this DateTimeOffset date)
=> new(date.Year, date.Month, date.Day, 23, 59, 59, 999, date.Offset);
/// <summary>
/// Calculate age from birthdate
/// </summary>
public static int CalculateAge(this DateOnly birthDate)
{
var today = DateOnly.FromDateTime(DateTime.Today);
var age = today.Year - birthDate.Year;
if (birthDate > today.AddYears(-age))
age--;
return age;
}
/// <summary>
/// Calculate rental days
/// </summary>
public static int CalculateRentalDays(this DateTimeOffset start, DateTimeOffset end)
=> (int)Math.Ceiling((end - start).TotalDays);
}
// Extensions/DecimalExtensions.cs
public static class DecimalExtensions
{
/// <summary>
/// Format as Thai Baht
/// </summary>
public static string ToThb(this decimal amount)
=> $"{amount:N0} THB";
/// <summary>
/// Format as Thai Baht with decimals
/// </summary>
public static string ToThbDecimal(this decimal amount)
=> $"{amount:N2} THB";
/// <summary>
/// Round to 2 decimal places
/// </summary>
public static decimal RoundMoney(this decimal amount)
=> Math.Round(amount, 2, MidpointRounding.AwayFromZero);
/// <summary>
/// Check if zero
/// </summary>
public static bool IsZero(this decimal amount)
=> amount == 0m;
/// <summary>
/// Check if positive
/// </summary>
public static bool IsPositive(this decimal amount)
=> amount > 0m;
}
// Extensions/EntityExtensions.cs
public static class EntityExtensions
{
/// <summary>
/// Check if entity is new (not yet saved)
/// </summary>
public static bool IsNew(this Entity entity)
=> entity.GetId() == 0;
/// <summary>
/// Check if entity exists (already saved)
/// </summary>
public static bool Exists(this Entity entity)
=> entity.GetId() > 0;
}
// String
var truncated = "Very long text".Truncate(10); // "Very lo..."
var phone = "0812345678".FormatThaiPhone(); // "081-234-5678"
// Collection
m_rentals.AddOrReplace(rental, r => r.RentalId == rental.RentalId);
m_items.ClearAndAddRange(newItems);
// DateTime
var thaiNow = DateTimeExtensions.ThailandNow();
var displayDate = rental.StartDate.ToThaiDateString(); // "07 Jan 2026"
var days = rental.StartDate.CalculateRentalDays(rental.ExpectedEndDate);
// Decimal
var display = rental.TotalAmount.ToThb(); // "3,500 THB"
MotoRent.Domain/
└── Extensions/
├── StringExtensions.cs
├── CollectionExtensions.cs
├── DateTimeExtensions.cs
├── DecimalExtensions.cs
└── EntityExtensions.cs