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。
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...
}
}
我厌倦了乏味的空检查,而拉值从MySqlDataReader,所以:
public static DateTime? GetNullableDateTime(this MySqlDataReader dr, string fieldName)
{
DateTime? nullDate = null;
return dr.IsDBNull(dr.GetOrdinal(fieldName)) ? nullDate : dr.GetDateTime(fieldName);
}
public static string GetNullableString(this MySqlDataReader dr, string fieldName)
{
return dr.IsDBNull(dr.GetOrdinal(fieldName)) ? String.Empty : dr.GetString(fieldName);
}
public static char? GetNullableChar(this MySqlDataReader dr, string fieldName)
{
char? nullChar = null;
return dr.IsDBNull(dr.GetOrdinal(fieldName)) ? nullChar : dr.GetChar(fieldName);
}
当然,这可以用于任何SqlDataReader。
hangy和Joe都对如何做到这一点提出了一些很好的意见,我也有机会在不同的环境中实现类似的东西,所以这里是另一个版本:
public static int? GetNullableInt32(this IDataRecord dr, int ordinal)
{
int? nullInt = null;
return dr.IsDBNull(ordinal) ? nullInt : dr.GetInt32(ordinal);
}
public static int? GetNullableInt32(this IDataRecord dr, string fieldname)
{
int ordinal = dr.GetOrdinal(fieldname);
return dr.GetNullableInt32(ordinal);
}
public static bool? GetNullableBoolean(this IDataRecord dr, int ordinal)
{
bool? nullBool = null;
return dr.IsDBNull(ordinal) ? nullBool : dr.GetBoolean(ordinal);
}
public static bool? GetNullableBoolean(this IDataRecord dr, string fieldname)
{
int ordinal = dr.GetOrdinal(fieldname);
return dr.GetNullableBoolean(ordinal);
}
// 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 ];
}
}
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");
..
而与MVC工作,有很多if语句,我只关心或真或假,打印null,或字符串。在另一种情况下,我想到了:
public static TResult WhenTrue<TResult>(this Boolean value, Func<TResult> expression)
{
return value ? expression() : default(TResult);
}
public static TResult WhenTrue<TResult>(this Boolean value, TResult content)
{
return value ? content : default(TResult);
}
public static TResult WhenFalse<TResult>(this Boolean value, Func<TResult> expression)
{
return !value ? expression() : default(TResult);
}
public static TResult WhenFalse<TResult>(this Boolean value, TResult content)
{
return !value ? content : default(TResult);
}
它允许我改变<%= (someBool) ?print y:字符串。将%>空为<%= someBool。WhenTrue("print y") %>。
我只在我的视图中使用它,在这里我混合了代码和HTML,在代码文件中编写“更长的”版本更清楚。