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。
字符串。As<T>,可用于将字符串值转换为某种类型(主要用于支持IConvertable的原语和类型)。工作伟大的空类型,甚至枚举!
public static partial class StringExtensions
{
/// <summary>
/// Converts the string to the specified type, using the default value configured for the type.
/// </summary>
/// <typeparam name="T">Type the string will be converted to. The type must implement IConvertable.</typeparam>
/// <param name="original">The original string.</param>
/// <returns>The converted value.</returns>
public static T As<T>(this String original)
{
return As(original, CultureInfo.CurrentCulture,
default(T));
}
/// <summary>
/// Converts the string to the specified type, using the default value configured for the type.
/// </summary>
/// <typeparam name="T">Type the string will be converted to.</typeparam>
/// <param name="original">The original string.</param>
/// <param name="defaultValue">The default value to use in case the original string is null or empty, or can't be converted.</param>
/// <returns>The converted value.</returns>
public static T As<T>(this String original, T defaultValue)
{
return As(original, CultureInfo.CurrentCulture, defaultValue);
}
/// <summary>
/// Converts the string to the specified type, using the default value configured for the type.
/// </summary>
/// <typeparam name="T">Type the string will be converted to.</typeparam>
/// <param name="original">The original string.</param>
/// <param name="provider">Format provider used during the type conversion.</param>
/// <returns>The converted value.</returns>
public static T As<T>(this String original, IFormatProvider provider)
{
return As(original, provider, default(T));
}
/// <summary>
/// Converts the string to the specified type.
/// </summary>
/// <typeparam name="T">Type the string will be converted to.</typeparam>
/// <param name="original">The original string.</param>
/// <param name="provider">Format provider used during the type conversion.</param>
/// <param name="defaultValue">The default value to use in case the original string is null or empty, or can't be converted.</param>
/// <returns>The converted value.</returns>
/// <remarks>
/// If an error occurs while converting the specified value to the requested type, the exception is caught and the default is returned. It is strongly recommended you
/// do NOT use this method if it is important that conversion failures are not swallowed up.
///
/// This method is intended to be used to convert string values to primatives, not for parsing, converting, or deserializing complex types.
/// </remarks>
public static T As<T>(this String original, IFormatProvider provider,
T defaultValue)
{
T result;
Type type = typeof (T);
if (String.IsNullOrEmpty(original)) result = defaultValue;
else
{
// need to get the underlying type if T is Nullable<>.
if (type.IsNullableType())
{
type = Nullable.GetUnderlyingType(type);
}
try
{
// ChangeType doesn't work properly on Enums
result = type.IsEnum
? (T) Enum.Parse(type, original, true)
: (T) Convert.ChangeType(original, type, provider);
}
catch // HACK: what can we do to minimize or avoid raising exceptions as part of normal operation? custom string parsing (regex?) for well-known types? it would be best to know if you can convert to the desired type before you attempt to do so.
{
result = defaultValue;
}
}
return result;
}
}
这依赖于Type的另一个简单扩展:
/// <summary>
/// Extension methods for <see cref="Type"/>.
/// </summary>
public static class TypeExtensions
{
/// <summary>
/// Returns whether or not the specified type is <see cref="Nullable{T}"/>.
/// </summary>
/// <param name="type">A <see cref="Type"/>.</param>
/// <returns>True if the specified type is <see cref="Nullable{T}"/>; otherwise, false.</returns>
/// <remarks>Use <see cref="Nullable.GetUnderlyingType"/> to access the underlying type.</remarks>
public static bool IsNullableType(this Type type)
{
if (type == null) throw new ArgumentNullException("type");
return type.IsGenericType && type.GetGenericTypeDefinition().Equals(typeof (Nullable<>));
}
}
用法:
var someInt = "1".As<int>();
var someIntDefault = "bad value".As(1); // "bad value" won't convert, so the default value 1 is returned.
var someEnum = "Sunday".As<DayOfWeek>();
someEnum = "0".As<DayOfWeek>(); // returns Sunday
var someNullableEnum = "".As<DayOfWeek?>(null); // returns a null value since "" can't be converted
public static bool In<T>(this T source, params T[] list)
{
if(null==source) throw new ArgumentNullException("source");
return list.Contains(source);
}
允许我替换:
if(reallyLongIntegerVariableName == 1 ||
reallyLongIntegerVariableName == 6 ||
reallyLongIntegerVariableName == 9 ||
reallyLongIntegerVariableName == 11)
{
// do something....
}
and
if(reallyLongStringVariableName == "string1" ||
reallyLongStringVariableName == "string2" ||
reallyLongStringVariableName == "string3")
{
// do something....
}
and
if(reallyLongMethodParameterName == SomeEnum.Value1 ||
reallyLongMethodParameterName == SomeEnum.Value2 ||
reallyLongMethodParameterName == SomeEnum.Value3 ||
reallyLongMethodParameterName == SomeEnum.Value4)
{
// do something....
}
:
if(reallyLongIntegerVariableName.In(1,6,9,11))
{
// do something....
}
and
if(reallyLongStringVariableName.In("string1","string2","string3"))
{
// do something....
}
and
if(reallyLongMethodParameterName.In(SomeEnum.Value1, SomeEnum.Value2, SomeEnum.Value3, SomeEnum.Value4)
{
// do something....
}
ThrowIfArgumentIsNull是做空检查的好方法,我们都应该这样做。
public static class Extensions
{
public static void ThrowIfArgumentIsNull<T>(this T obj, string parameterName) where T : class
{
if (obj == null) throw new ArgumentNullException(parameterName + " not allowed to be null");
}
}
下面是使用它的方法,它适用于您的命名空间中的所有类或任何您使用该命名空间的地方。
internal class Test
{
public Test(string input1)
{
input1.ThrowIfArgumentIsNull("input1");
}
}
在CodePlex项目上使用这段代码是可以的。
在我的MiscUtil项目中有各种扩展方法(完整的源代码在那里可用-我不打算在这里重复它)。我最喜欢的,其中一些涉及其他类(如范围):
日期和时间——主要用于单元测试。我不确定我会在生产中使用它们:)
var birthday = 19.June(1976);
var workingDay = 7.Hours() + 30.Minutes();
范围和步进——非常感谢Marc Gravell的运算符使这成为可能:
var evenNaturals = 2.To(int.MaxValue).Step(2);
var daysSinceBirth = birthday.To(DateTime.Today).Step(1.Days());
比较:
var myComparer = ProjectionComparer.Create(Person p => p.Name);
var next = myComparer.ThenBy(p => p.Age);
var reversed = myComparer.Reverse();
参数检查:
x.ThrowIfNull("x");
LINQ to XML应用于匿名类型(或其他具有适当属性的类型):
// <Name>Jon</Name><Age>32</Age>
new { Name="Jon", Age=32}.ToXElements();
// Name="Jon" Age="32" (as XAttributes, obviously)
new { Name="Jon", Age=32}.ToXAttributes()
Push LINQ -在这里解释太长了,但是可以搜索一下。
为什么不呢!这是一个扩展到IList(不能是IEnumerable,因为我使用列表特定的功能)插入排序。
internal static class SortingHelpers
{
/// <summary>
/// Performs an insertion sort on this list.
/// </summary>
/// <typeparam name="T">The type of the list supplied.</typeparam>
/// <param name="list">the list to sort.</param>
/// <param name="comparison">the method for comparison of two elements.</param>
/// <returns></returns>
public static void InsertionSort<T>(this IList<T> list, Comparison<T> comparison)
{
for (int i = 2; i < list.Count; i++)
{
for (int j = i; j > 1 && comparison(list[j], list[j - 1]) < 0; j--)
{
T tempItem = list[j];
list.RemoveAt(j);
list.Insert(j - 1, tempItem);
}
}
}
}
一个例子:
List<int> list1 = { 3, 5, 1, 2, 9, 4, 6 };
list1.InsertionSort((a,b) => a - b);
//list is now in order of 1,2,3,4,5,6,9