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。
我的转换扩展，允许你做:
int i = myString.To<int>();
这是在TheSoftwareJedi.com上发布的
public static T To<T>(this IConvertible obj)
{
return (T)Convert.ChangeType(obj, typeof(T));
}
public static T ToOrDefault<T>
(this IConvertible obj)
{
try
{
return To<T>(obj);
}
catch
{
return default(T);
}
}
public static bool ToOrDefault<T>
(this IConvertible obj,
out T newObj)
{
try
{
newObj = To<T>(obj);
return true;
}
catch
{
newObj = default(T);
return false;
}
}
public static T ToOrOther<T>
(this IConvertible obj,
T other)
{
try
{
return To<T>obj);
}
catch
{
return other;
}
}
public static bool ToOrOther<T>
(this IConvertible obj,
out T newObj,
T other)
{
try
{
newObj = To<T>(obj);
return true;
}
catch
{
newObj = other;
return false;
}
}
public static T ToOrNull<T>
(this IConvertible obj)
where T : class
{
try
{
return To<T>(obj);
}
catch
{
return null;
}
}
public static bool ToOrNull<T>
(this IConvertible obj,
out T newObj)
where T : class
{
try
{
newObj = To<T>(obj);
return true;
}
catch
{
newObj = null;
return false;
}
}
您可以在失败时请求default(调用空白构造函数或“0”作为数字)，指定一个“default”值(我称之为“other”)，或请求null(其中T: class)。我还提供了两个静默异常模型和一个典型的TryParse模型，该模型返回一个bool值，指示所采取的操作，一个out参数保存新值。
我们的代码可以这样做
int i = myString.To<int>();
string a = myInt.ToOrDefault<string>();
//note type inference
DateTime d = myString.ToOrOther(DateTime.MAX_VALUE);
double d;
//note type inference
bool didItGiveDefault = myString.ToOrDefault(out d);
string s = myDateTime.ToOrNull<string>();
我不能让Nullable类型非常干净地滚入整个东西。我试了大约20分钟才认输。
public static class EnumerableExtensions
{
[Pure]
public static U MapReduce<T, U>(this IEnumerable<T> enumerable, Func<T, U> map, Func<U, U, U> reduce)
{
CodeContract.RequiresAlways(enumerable != null);
CodeContract.RequiresAlways(enumerable.Skip(1).Any());
CodeContract.RequiresAlways(map != null);
CodeContract.RequiresAlways(reduce != null);
return enumerable.AsParallel().Select(map).Aggregate(reduce);
}
[Pure]
public static U MapReduce<T, U>(this IList<T> list, Func<T, U> map, Func<U, U, U> reduce)
{
CodeContract.RequiresAlways(list != null);
CodeContract.RequiresAlways(list.Count >= 2);
CodeContract.RequiresAlways(map != null);
CodeContract.RequiresAlways(reduce != null);
U result = map(list[0]);
for (int i = 1; i < list.Count; i++)
{
result = reduce(result,map(list[i]));
}
return result;
}
//Parallel version; creates garbage
[Pure]
public static U MapReduce<T, U>(this IList<T> list, Func<T, U> map, Func<U, U, U> reduce)
{
CodeContract.RequiresAlways(list != null);
CodeContract.RequiresAlways(list.Skip(1).Any());
CodeContract.RequiresAlways(map != null);
CodeContract.RequiresAlways(reduce != null);
U[] mapped = new U[list.Count];
Parallel.For(0, mapped.Length, i =>
{
mapped[i] = map(list[i]);
});
U result = mapped[0];
for (int i = 1; i < list.Count; i++)
{
result = reduce(result, mapped[i]);
}
return result;
}
}
通过操作系统文件系统信息比较文件/目录。这对于比较共享和本地文件非常有用。
用法:
DirectoryInfo dir = new DirectoryInfo(@"C:\test\myShareDir");
Console.WriteLine(dir.IsSameFileAs(@"\\myMachineName\myShareDir"));
FileInfo file = new FileInfo(@"C:\test\myShareDir\file.txt");
Console.WriteLine(file.IsSameFileAs(@"\\myMachineName\myShareDir\file.txt"));
代码:
public static class FileExtensions
{
struct BY_HANDLE_FILE_INFORMATION
{
public uint FileAttributes;
public System.Runtime.InteropServices.ComTypes.FILETIME CreationTime;
public System.Runtime.InteropServices.ComTypes.FILETIME LastAccessTime;
public System.Runtime.InteropServices.ComTypes.FILETIME LastWriteTime;
public uint VolumeSerialNumber;
public uint FileSizeHigh;
public uint FileSizeLow;
public uint NumberOfLinks;
public uint FileIndexHigh;
public uint FileIndexLow;
}
//
// CreateFile constants
//
const uint FILE_SHARE_READ = 0x00000001;
const uint OPEN_EXISTING = 3;
const uint GENERIC_READ = (0x80000000);
const uint FILE_FLAG_BACKUP_SEMANTICS = 0x02000000;
[DllImport("kernel32.dll", SetLastError = true)]
static extern IntPtr CreateFile(
string lpFileName,
uint dwDesiredAccess,
uint dwShareMode,
IntPtr lpSecurityAttributes,
uint dwCreationDisposition,
uint dwFlagsAndAttributes,
IntPtr hTemplateFile);
[DllImport("kernel32.dll", SetLastError = true)]
static extern bool GetFileInformationByHandle(IntPtr hFile, out BY_HANDLE_FILE_INFORMATION lpFileInformation);
public static bool IsSameFileAs(this FileSystemInfo file, string path)
{
BY_HANDLE_FILE_INFORMATION fileInfo1, fileInfo2;
IntPtr ptr1 = CreateFile(file.FullName, GENERIC_READ, FILE_SHARE_READ, IntPtr.Zero, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, IntPtr.Zero);
if ((int)ptr1 == -1)
{
System.ComponentModel.Win32Exception e = new System.ComponentModel.Win32Exception(Marshal.GetLastWin32Error());
throw e;
}
IntPtr ptr2 = CreateFile(path, GENERIC_READ, FILE_SHARE_READ, IntPtr.Zero, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, IntPtr.Zero);
if ((int)ptr2 == -1)
{
System.ComponentModel.Win32Exception e = new System.ComponentModel.Win32Exception(Marshal.GetLastWin32Error());
throw e;
}
GetFileInformationByHandle(ptr1, out fileInfo1);
GetFileInformationByHandle(ptr2, out fileInfo2);
return ((fileInfo1.FileIndexHigh == fileInfo2.FileIndexHigh) &&
(fileInfo1.FileIndexLow == fileInfo2.FileIndexLow));
}
}
