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。
我最常用的扩展是一个可以格式化字节数组:
/// <summary>
/// Returns a string representation of a byte array.
/// </summary>
/// <param name="bytearray">The byte array to represent.</param>
/// <param name="subdivision">The number of elements per group,
/// or 0 to not restrict it. The default is 0.</param>
/// <param name="subsubdivision">The number of elements per line,
/// or 0 to not restrict it. The default is 0.</param>
/// <param name="divider">The string dividing the individual bytes. The default is " ".</param>
/// <param name="subdivider">The string dividing the groups. The default is " ".</param>
/// <param name="subsubdivider">The string dividing the lines. The default is "\r\n".</param>
/// <param name="uppercase">Whether the representation is in uppercase hexadecimal.
/// The default is <see langword="true"/>.</param>
/// <param name="prebyte">The string to put before each byte. The default is an empty string.</param>
/// <param name="postbyte">The string to put after each byte. The default is an empty string.</param>
/// <returns>The string representation.</returns>
/// <exception cref="ArgumentNullException">
/// <paramref name="bytearray"/> is <see langword="null"/>.
/// </exception>
public static string ToArrayString(this byte[] bytearray,
int subdivision = 0,
int subsubdivision = 0,
string divider = " ",
string subdivider = " ",
string subsubdivider = "\r\n",
bool uppercase = true,
string prebyte = "",
string postbyte = "")
{
#region Contract
if (bytearray == null)
throw new ArgumentNullException("bytearray");
#endregion
StringBuilder sb = new StringBuilder(
bytearray.Length * (2 + divider.Length + prebyte.Length + postbyte.Length) +
(subdivision > 0 ? (bytearray.Length / subdivision) * subdivider.Length : 0) +
(subsubdivision > 0 ? (bytearray.Length / subsubdivision) * subsubdivider.Length : 0));
int groupElements = (subdivision > 0 ? subdivision - 1 : -1);
int lineElements = (subsubdivision > 0 ? subsubdivision - 1 : -1);
for (long i = 0; i < bytearray.LongLength - 1; i++)
{
sb.Append(prebyte);
sb.Append(String.Format(CultureInfo.InvariantCulture, (uppercase ? "{0:X2}" : "{0:x2}"), bytearray[i]));
sb.Append(postbyte);
if (lineElements == 0)
{
sb.Append(subsubdivider);
groupElements = subdivision;
lineElements = subsubdivision;
}
else if (groupElements == 0)
{
sb.Append(subdivider);
groupElements = subdivision;
}
else
sb.Append(divider);
lineElements--;
groupElements--;
}
sb.Append(prebyte);
sb.Append(String.Format(CultureInfo.InvariantCulture, (uppercase ? "{0:X2}" : "{0:x2}"), bytearray[bytearray.LongLength - 1]));
sb.Append(postbyte);
return sb.ToString();
}
默认情况下,ToArrayString()只是将字节数组打印为由单个字节组成的长字符串。但是,ToArrayString(4,16)将字节分组为4个一组,一行16个字节,就像在您最喜欢的十六进制编辑器中一样。下面很好地格式化了字节数组,以便在c#代码中使用:
byte[] bytearray = new byte[]{ ... };
Console.Write(bytearray.ToArrayString(4, 16, ", ", ", ", ",\r\n", true, "0x"));
这是我写的,所以你可以用Codeplex。
我今天刚刚在博客上写了这个。它是INotifyPropertyChanged属性周围的强类型响应式包装器。
GetPropertyValues返回一个IObservable<T>的值,当它们改变时,从当前值开始。如果忽略当前值,可以对结果调用Skip(1)。
用法如下:
IObservable<int> values = viewModel.GetPropertyValues(x => x.IntProperty);
实现:
public static class NotifyPropertyChangeReactiveExtensions
{
// Returns the values of property (an Expression) as they change,
// starting with the current value
public static IObservable<TValue> GetPropertyValues<TSource, TValue>(
this TSource source, Expression<Func<TSource, TValue>> property)
where TSource : INotifyPropertyChanged
{
MemberExpression memberExpression = property.Body as MemberExpression;
if (memberExpression == null)
{
throw new ArgumentException(
"property must directly access a property of the source");
}
string propertyName = memberExpression.Member.Name;
Func<TSource, TValue> accessor = property.Compile();
return source.GetPropertyChangedEvents()
.Where(x => x.EventArgs.PropertyName == propertyName)
.Select(x => accessor(source))
.StartWith(accessor(source));
}
// This is a wrapper around FromEvent(PropertyChanged)
public static IObservable<IEvent<PropertyChangedEventArgs>>
GetPropertyChangedEvents(this INotifyPropertyChanged source)
{
return Observable.FromEvent<PropertyChangedEventHandler,
PropertyChangedEventArgs>(
h => new PropertyChangedEventHandler(h),
h => source.PropertyChanged += h,
h => source.PropertyChanged -= h);
}
}
For adding multiple elements to a collection that doesn't have AddRange, e.g., collection.Add(item1, item2, itemN);
static void Add<T>(this ICollection<T> coll, params T[] items)
{ foreach (var item in items) coll.Add(item);
}
The following is like string.Format() but with custom string representation of arguments, e.g., "{0} {1} {2}".Format<Custom>(c=>c.Name,"string",new object(),new Custom()) results in "string {System.Object} Custom1Name"
static string Format<T>( this string format
, Func<T,object> select
, params object[] args)
{ for(int i=0; i < args.Length; ++i)
{ var x = args[i] as T;
if (x != null) args[i] = select(x);
}
return string.Format(format, args);
}
在单元测试中很有用:
public static IList<T> Clone<T>(this IList<T> list) where T : ICloneable
{
var ret = new List<T>(list.Count);
foreach (var item in list)
ret.Add((T)item.Clone());
// done
return ret;
}
像TWith2Sugars这样的一系列,交替缩短语法:
public static long? ToNullableInt64(this string val)
{
long ret;
return Int64.TryParse(val, out ret) ? ret : new long?();
}
最后,在BCL中是否已经有一些东西做了下面的事情?
public static void Split<T>(this T[] array,
Func<T,bool> determinator,
IList<T> onTrue,
IList<T> onFalse)
{
if (onTrue == null)
onTrue = new List<T>();
else
onTrue.Clear();
if (onFalse == null)
onFalse = new List<T>();
else
onFalse.Clear();
if (determinator == null)
return;
foreach (var item in array)
{
if (determinator(item))
onTrue.Add(item);
else
onFalse.Add(item);
}
}
二分查找:
public static T BinarySearch<T, TKey>(this IList<T> list, Func<T, TKey> keySelector, TKey key)
where TKey : IComparable<TKey>
{
int min = 0;
int max = list.Count;
int index = 0;
while (min < max)
{
int mid = (max + min) / 2;
T midItem = list[mid];
TKey midKey = keySelector(midItem);
int comp = midKey.CompareTo(key);
if (comp < 0)
{
min = mid + 1;
}
else if (comp > 0)
{
max = mid - 1;
}
else
{
return midItem;
}
}
if (min == max &&
keySelector(list[min]).CompareTo(key) == 0)
{
return list[min];
}
throw new InvalidOperationException("Item not found");
}
用法(假设列表按Id排序):
var item = list.BinarySearch(i => i.Id, 42);
它抛出InvalidOperationException的事实可能看起来很奇怪,但这就是Enumerable。第一种情况是没有匹配项。