让我们把你的优秀和最喜欢的扩展方法列一个列表。
要求是必须发布完整的代码，以及如何使用它的示例和解释。
基于对这个主题的高度兴趣，我在Codeplex上建立了一个名为extensionoverflow的开源项目。
请将您的回答标记为接受，以便将代码放入Codeplex项目。
请张贴完整的源代码，而不是一个链接。
Codeplex上新闻:
24.08.2010 Codeplex页面现在在这里:http://extensionoverflow.codeplex.com/
11.11.2008 XmlSerialize / XmlDeserialize现在是实现和单元测试。
11.11.2008仍有发展空间。;-)现在就加入!
11.11.2008第三位贡献者加入了ExtensionOverflow，欢迎加入BKristensen
11.11.2008 FormatWith现在是实现和单元测试。
09.11.2008第二个贡献者加入ExtensionOverflow。欢迎来到chakrit。
我们需要更多的开发人员。: -)
09.11.2008 ThrowIfArgumentIsNull现已在Codeplex上实现和单元测试。
下面是我用来减少提取单个属性的一些方法:
public static T GetAttribute<T>(this ICustomAttributeProvider provider, bool inherit = false, int index = 0) where T : Attribute
{
return provider.GetAttribute(typeof(T), inherit, index) as T;
}
public static Attribute GetAttribute(this ICustomAttributeProvider provider, Type type, bool inherit = false, int index = 0)
{
bool exists = provider.IsDefined(type, inherit);
if (!exists)
{
return null;
}
object[] attributes = provider.GetCustomAttributes(type, inherit);
if (attributes != null && attributes.Length != 0)
{
return attributes[index] as Attribute;
}
else
{
return null;
}
}
用法(枚举描述hack的实现):
public static string GetDescription(this Enum value)
{
var fieldInfo = value.GetType().GetField(value.ToString());
var attribute = fieldInfo.GetAttribute<DescriptionAttribute>();
return attribute != null ? attribute.Description : null;
}
请随意将其包含在CodePlex项目中!
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;
}
这是我今天刚创建的一个。
// requires .NET 4
public static TReturn NullOr<TIn, TReturn>(this TIn obj, Func<TIn, TReturn> func,
TReturn elseValue = default(TReturn)) where TIn : class
{ return obj != null ? func(obj) : elseValue; }
// versions for CLR 2, which doesn't support optional params
public static TReturn NullOr<TIn, TReturn>(this TIn obj, Func<TIn, TReturn> func,
TReturn elseValue) where TIn : class
{ return obj != null ? func(obj) : elseValue; }
public static TReturn NullOr<TIn, TReturn>(this TIn obj, Func<TIn, TReturn> func)
where TIn : class
{ return obj != null ? func(obj) : default(TReturn); }
它让你这样做:
var lname = thingy.NullOr(t => t.Name).NullOr(n => n.ToLower());
哪个比这个更流畅，(依我看)更容易阅读:
var lname = (thingy != null ? thingy.Name : null) != null
? thingy.Name.ToLower() : null;
使用反射查找TryParse方法并在字符串目标上调用它。可选参数指定转换失败时应返回的内容。我发现这个方法在大多数时候都很有用。很清楚皈依者。ChangeType选项，但我发现这更有用的什么与默认结果方便和什么。请注意，找到的方法保存在字典中，尽管我确实怀疑装箱最终会降低一点速度。
这种方法是我最喜欢的，因为它合理地使用了许多语言特性。
private static readonly Dictionary<Type, MethodInfo> Parsers = new Dictionary<Type, MethodInfo>();
public static T Parse<T>(this string value, T defaultValue = default(T))
{
if (string.IsNullOrEmpty(value)) return defaultValue;
if (!Parsers.ContainsKey(typeof(T)))
Parsers[typeof (T)] = typeof (T).GetMethods(BindingFlags.Public | BindingFlags.Static)
.Where(mi => mi.Name == "TryParse")
.Single(mi =>
{
var parameters = mi.GetParameters();
if (parameters.Length != 2) return false;
return parameters[0].ParameterType == typeof (string) &&
parameters[1].ParameterType == typeof (T).MakeByRefType();
});
var @params = new object[] {value, default(T)};
return (bool) Parsers[typeof (T)].Invoke(null, @params) ?
(T) @params[1] : defaultValue;
}
用法:
var hundredTwentyThree = "123".Parse(0);
var badnumber = "test".Parse(-1);
var date = "01/01/01".Parse<DateTime>();
