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。
// This file contains extension methods for generic List<> class to operate on sorted lists.
// Duplicate values are OK.
// O(ln(n)) is still much faster then the O(n) of LINQ's searches/filters.
static partial class SortedList
{
// Return the index of the first element with the key greater then provided.
// If there's no such element within the provided range, it returns iAfterLast.
public static int sortedFirstGreaterIndex<tElt, tKey>( this IList<tElt> list, Func<tElt, tKey, int> comparer, tKey key, int iFirst, int iAfterLast )
{
if( iFirst < 0 || iAfterLast < 0 || iFirst > list.Count || iAfterLast > list.Count )
throw new IndexOutOfRangeException();
if( iFirst > iAfterLast )
throw new ArgumentException();
if( iFirst == iAfterLast )
return iAfterLast;
int low = iFirst, high = iAfterLast;
// The code below is inspired by the following article:
// http://en.wikipedia.org/wiki/Binary_search#Single_comparison_per_iteration
while( low < high )
{
int mid = ( high + low ) / 2;
// 'mid' might be 'iFirst' in case 'iFirst+1 == iAfterLast'.
// 'mid' will never be 'iAfterLast'.
if( comparer( list[ mid ], key ) <= 0 ) // "<=" since we gonna find the first "greater" element
low = mid + 1;
else
high = mid;
}
return low;
}
// Return the index of the first element with the key greater then the provided key.
// If there's no such element, returns list.Count.
public static int sortedFirstGreaterIndex<tElt, tKey>( this IList<tElt> list, Func<tElt, tKey, int> comparer, tKey key )
{
return list.sortedFirstGreaterIndex( comparer, key, 0, list.Count );
}
// Add an element to the sorted array.
// This could be an expensive operation if frequently adding elements that sort firstly.
// This is cheap operation when adding elements that sort near the tail of the list.
public static int sortedAdd<tElt>( this List<tElt> list, Func<tElt, tElt, int> comparer, tElt elt )
{
if( list.Count == 0 || comparer( list[ list.Count - 1 ], elt ) <= 0 )
{
// either the list is empty, or the item is greater then all elements already in the collection.
list.Add( elt );
return list.Count - 1;
}
int ind = list.sortedFirstGreaterIndex( comparer, elt );
list.Insert( ind, elt );
return ind;
}
// Find first exactly equal element, return -1 if not found.
public static int sortedFindFirstIndex<tElt, tKey>( this List<tElt> list, Func<tElt, tKey, int> comparer, tKey elt )
{
int low = 0, high = list.Count - 1;
while( low < high )
{
int mid = ( high + low ) / 2;
if( comparer( list[ mid ], elt ) < 0 )
low = mid + 1;
else
high = mid; // this includes the case when we've found an element exactly matching the key
}
if( high >= 0 && 0 == comparer( list[ high ], elt ) )
return high;
return -1;
}
// Return the IEnumerable that returns array elements in the reverse order.
public static IEnumerable<tElt> sortedReverse<tElt>( this List<tElt> list )
{
for( int i=list.Count - 1; i >= 0; i-- )
yield return list[ i ];
}
}
一些用于使用列表的扩展:
/// <summary>
/// Wrap an object in a list
/// </summary>
public static IList<T> WrapInList<T>(this T item)
{
List<T> result = new List<T>();
result.Add(item);
return result;
}
使用如:
myList = someObject.InList();
使IEnumerable包含来自一个或多个源的项,以使IEnumerable更像列表。对于高性能代码来说,这可能不是一个好主意,但对于测试来说很有用:
public static IEnumerable<T> Append<T>(this IEnumerable<T> enumerable, T newItem)
{
foreach (T item in enumerable)
{
yield return item;
}
yield return newItem;
}
public static IEnumerable<T> Append<T>(this IEnumerable<T> enumerable, params T[] newItems)
{
foreach (T item in enumerable)
{
yield return item;
}
foreach (T newItem in newItems)
{
yield return newItem;
}
}
如使用。
someEnumeration = someEnumeration.Append(newItem);
还有其他可能的变化——例如。
someEnumeration = someEnumeration.Append(otherEnumeration);
如果你正在克隆项目,你可能还想克隆它们的列表:
public static IList<T> Clone<T>(this IEnumerable<T> source) where T: ICloneable
{
List<T> result = new List<T>();
foreach (T item in source)
{
result.Add((T)item.Clone());
}
return result;
}
当我使用ObservableCollection<T>时,我通常使用AddRange方法扩展它。这里的其他答案给出了这个的实现。
如果您愿意,可以将此代码放入Codeplex项目中。
字符串。格式的快捷方式:
public static class StringExtensions
{
// Enable quick and more natural string.Format calls
public static string F(this string s, params object[] args)
{
return string.Format(s, args);
}
}
例子:
var s = "The co-ordinate is ({0}, {1})".F(point.X, point.Y);
要快速复制粘贴,请点击这里。
难道你不觉得输入“一些字符串”. f(“param”)而不是字符串更自然吗?格式(“一些字符串”,“参数”)?
想要一个更容易读懂的名字,试试下面的建议:
s = "Hello {0} world {1}!".Fmt("Stack", "Overflow");
s = "Hello {0} world {1}!".FormatBy("Stack", "Overflow");
s = "Hello {0} world {1}!".FormatWith("Stack", "Overflow");
s = "Hello {0} world {1}!".Display("Stack", "Overflow");
s = "Hello {0} world {1}!".With("Stack", "Overflow");
..