我使用以下扩展来扩展所有的集合(也许有人发现这些有用):

/// <summary>
/// Collection Helper
/// </summary>
/// <remarks>
/// Use IEnumerable by default, but when altering or getting item at index use IList.
/// </remarks>
public static class CollectionHelper
{

    #region Alter;

    /// <summary>
    /// Swap item to another place
    /// </summary>
    /// <typeparam name="T">Collection type</typeparam>
    /// <param name="this">Collection</param>
    /// <param name="IndexA">Index a</param>
    /// <param name="IndexB">Index b</param>
    /// <returns>New collection</returns>
    public static IList<T> Swap<T>(this IList<T> @this, Int32 IndexA, Int32 IndexB)
    {
        T Temp = @this[IndexA];
        @this[IndexA] = @this[IndexB];
        @this[IndexB] = Temp;
        return @this;
    }

    /// <summary>
    /// Swap item to the left
    /// </summary>
    /// <typeparam name="T">Collection type</typeparam>
    /// <param name="this">Collection</param>
    /// <param name="Index">Index</param>
    /// <returns>New collection</returns>
    public static IList<T> SwapLeft<T>(this IList<T> @this, Int32 Index)
    {
        return @this.Swap(Index, Index - 1);
    }

    /// <summary>
    /// Swap item to the right
    /// </summary>
    /// <typeparam name="T">Collection type</typeparam>
    /// <param name="this">Collection</param>
    /// <param name="Index">Index</param>
    /// <returns>New collection</returns>
    public static IList<T> SwapRight<T>(this IList<T> @this, Int32 Index)
    {
        return @this.Swap(Index, Index + 1);
    }

    #endregion Alter;

    #region Action;

    /// <summary>
    /// Execute action at specified index
    /// </summary>
    /// <typeparam name="T">Collection type</typeparam>
    /// <param name="this">Collection</param>
    /// <param name="Index">Index</param>
    /// <param name="ActionAt">Action to execute</param>
    /// <returns>New collection</returns>
    public static IList<T> ActionAt<T>(this IList<T> @this, Int32 Index, Action<T> ActionAt)
    {
        ActionAt(@this[Index]);
        return @this;
    }

    #endregion Action;

    #region Randomize;

    /// <summary>
    /// Take random items
    /// </summary>
    /// <typeparam name="T">Collection type</typeparam>
    /// <param name="this">Collection</param>
    /// <param name="Count">Number of items to take</param>
    /// <returns>New collection</returns>
    public static IEnumerable<T> TakeRandom<T>(this IEnumerable<T> @this, Int32 Count)
    {
        return @this.Shuffle().Take(Count);
    }

    /// <summary>
    /// Take random item
    /// </summary>
    /// <typeparam name="T">Collection type</typeparam>
    /// <param name="this">Collection</param>
    /// <returns>Item</returns>
    public static T TakeRandom<T>(this IEnumerable<T> @this)
    {
        return @this.TakeRandom(1).Single();
    }

    /// <summary>
    /// Shuffle list
    /// </summary>
    /// <typeparam name="T">Collection type</typeparam>
    /// <param name="this">Collection</param>
    /// <returns>New collection</returns>
    public static IEnumerable<T> Shuffle<T>(this IEnumerable<T> @this)
    {
        return @this.OrderBy(Item => Guid.NewGuid());
    }

    #endregion Randomize;

    #region Navigate;

    /// <summary>
    /// Get next item in collection and give first item, when last item is selected;
    /// </summary>
    /// <typeparam name="T">Collection type</typeparam>
    /// <param name="this">Collection</param>
    /// <param name="Index">Index in collection</param>
    /// <returns>Next item</returns>
    public static T Next<T>(this IList<T> @this, ref Int32 Index)
    {
        Index = ++Index >= 0 && Index < @this.Count ? Index : 0;
        return @this[Index];
    }

    /// <summary>
    /// Get previous item in collection and give last item, when first item is selected;
    /// </summary>
    /// <typeparam name="T">Collection type</typeparam>
    /// <param name="this">Collection</param>
    /// <param name="Index">Index in collection</param>
    /// <returns>Previous item</returns>
    public static T Previous<T>(this IList<T> @this, ref Int32 Index)
    {
        Index = --Index >= 0 && Index < @this.Count ? Index : @this.Count - 1;
        return @this[Index];
    }

    #endregion Navigate;

    #region Clone;

    /// <summary>
    /// 
    /// </summary>
    /// <typeparam name="T">Collection type</typeparam>
    /// <param name="this">Collection</param>
    /// <returns>Cloned collection</returns>
    public static IEnumerable<T> Clone<T>(this IEnumerable<T> @this) where T : ICloneable
    {
        return @this.Select(Item => (T)Item.Clone());
    }

    #endregion Clone;

    #region String;

    /// <summary>
    /// Joins multiple string with Separator
    /// </summary>
    /// <param name="this">Collection</param>
    /// <param name="Separator">Separator</param>
    /// <returns>Joined string</returns>
    public static String Join(this IEnumerable<String> @this, String Separator = "")
    {
        return String.Join(Separator, @this);
    }

    #endregion String;

}

类似于上面的字符串As和Is，但对所有对象都是全局的。

这很简单，但我经常使用这些方法来缓解拳击中的parens爆炸。

public static class ExtensionMethods_Object
{
    [DebuggerStepThrough()]
    public static bool Is<T>(this object item) where T : class
    {
        return item is T;
    }

    [DebuggerStepThrough()]
    public static bool IsNot<T>(this object item) where T : class
    {
        return !(item.Is<T>());
    }

    [DebuggerStepThrough()]
    public static T As<T>(this object item) where T : class
    {
        return item as T;
    }
}

我很高兴这段代码能在codeplex上使用，事实上它已经在使用了。

// Checks for an empty collection, and sends the value set in the default constructor for the desired field
public static TResult MinGuarded<T, TResult>(this IEnumerable<T> items, Func<T, TResult> expression) where T : new() {
    if(items.IsEmpty()) {
        return (new List<T> { new T() }).Min(expression);
    }
    return items.Min(expression);
}

// Checks for an empty collection, and sends the value set in the default constructor for the desired field
public static TResult MaxGuarded<T, TResult>(this IEnumerable<T> items, Func<T, TResult> expression) where T : new() {
    if(items.IsEmpty()) {
        return (new List<T> { new T() }).Max(expression);
    }
    return items.Max(expression);
}

我不确定是否有更好的方法来做到这一点，但这个扩展是非常有用的，每当我想要控制我的对象中的字段的默认值。 例如，如果我想控制DateTime的值，并希望根据我的业务逻辑进行设置，那么我可以在默认构造函数中这样做。否则，它将显示为DateTime.MinDate。

public static class ComparableExtensions
{
  public static bool Between<T>(this T actual, T lower, T upper) where T : IComparable<T>
  {
    return actual.CompareTo(lower) >= 0 && actual.CompareTo(upper) < 0;
  }
}

例子:

if (myNumber.Between(3,7))
{
  // ....
}

我不想添加任何已经说过的东西，所以这里有一些我没有提到的东西。(如果这太长了，对不起):

public static class MyExtensions
{
    public static bool IsInteger(this string input)
    {
        int temp;

        return int.TryParse(input, out temp);
    }

    public static bool IsDecimal(this string input)
    {
        decimal temp;

        return decimal.TryParse(input, out temp);
    }

    public static int ToInteger(this string input, int defaultValue)
    {
        int temp;

        return (int.TryParse(input, out temp)) ? temp : defaultValue;
    }

    public static decimal ToDecimal(this string input, decimal defaultValue)
    {
        decimal temp;

        return (decimal.TryParse(input, out temp)) ? temp : defaultValue;
    }

    public static DateTime ToFirstOfTheMonth(this DateTime input)
    {
        return input.Date.AddDays(-1 * input.Day + 1);
    }

    // Intentionally returns 0 if the target date is before the input date.
    public static int MonthsUntil(this DateTime input, DateTime targetDate)
    {
        input = input.ToFirstOfTheMonth();

        targetDate = targetDate.ToFirstOfTheMonth();

        int result = 0;

        while (input < targetDate)
        {
        input = input.AddMonths(1);
            result++;
        }

        return result;
    }

    // Used for backwards compatibility in a system built before my time.
    public static DataTable ToDataTable(this IEnumerable input)
    {
        // too much code to show here right now...
    }
}

我的转换扩展，允许你做:

int i = myString.To<int>();

这是在TheSoftwareJedi.com上发布的

public static T To<T>(this IConvertible obj)
{
  return (T)Convert.ChangeType(obj, typeof(T));
}

public static T ToOrDefault<T>
             (this IConvertible obj)
{
    try
    {
        return To<T>(obj);
    }
    catch
    {
        return default(T);
    }
}

public static bool ToOrDefault<T>
                    (this IConvertible obj,
                     out T newObj)
{
    try
    {
        newObj = To<T>(obj); 
        return true;
    }
    catch
    {
        newObj = default(T); 
        return false;
    }
}

public static T ToOrOther<T>
                       (this IConvertible obj,
                       T other)
{
  try
  {
      return To<T>obj);
  }
  catch
  {
      return other;
  }
}

public static bool ToOrOther<T>
                         (this IConvertible obj,
                         out T newObj,
                         T other)
{
    try
    {
        newObj = To<T>(obj);
        return true;
    }
    catch
    {
        newObj = other;
        return false;
    }
}

public static T ToOrNull<T>
                      (this IConvertible obj)
                      where T : class
{
    try
    {
        return To<T>(obj);
    }
    catch
    {
        return null;
    }
}

public static bool ToOrNull<T>
                  (this IConvertible obj,
                  out T newObj)
                  where T : class
{
    try
    {
        newObj = To<T>(obj);
        return true;
    }
    catch
    {
        newObj = null;
        return false;
    }
}

您可以在失败时请求default(调用空白构造函数或“0”作为数字)，指定一个“default”值(我称之为“other”)，或请求null(其中T: class)。我还提供了两个静默异常模型和一个典型的TryParse模型，该模型返回一个bool值，指示所采取的操作，一个out参数保存新值。 我们的代码可以这样做

int i = myString.To<int>();
string a = myInt.ToOrDefault<string>();
//note type inference
DateTime d = myString.ToOrOther(DateTime.MAX_VALUE);
double d;
//note type inference
bool didItGiveDefault = myString.ToOrDefault(out d);
string s = myDateTime.ToOrNull<string>();

我不能让Nullable类型非常干净地滚入整个东西。我试了大约20分钟才认输。