这一次是为了使UriBuilder在处理查询参数时更加友好。

    /// <summary>
    /// Adds the specified query parameter to the URI builder.
    /// </summary>
    /// <param name="builder">The builder.</param>
    /// <param name="parameterName">Name of the parameter.</param>
    /// <param name="value">The URI escaped value.</param>
    /// <returns>The final full query string.</returns>
    public static string AddQueryParam(this UriBuilder builder, string parameterName, string value)
    {
        if (parameterName == null)
            throw new ArgumentNullException("parameterName");

        if (parameterName.Length == 0)
            throw new ArgumentException("The parameter name is empty.");

        if (value == null)
            throw new ArgumentNullException("value");

        if (value.Length == 0)
            throw new ArgumentException("The value is empty.");

        if (builder.Query.Length == 0)
        {
            builder.Query = String.Concat(parameterName, "=", value);
        }
        else if
            (builder.Query.Contains(String.Concat("&", parameterName, "="))
            || builder.Query.Contains(String.Concat("?", parameterName, "=")))
        {
            throw new InvalidOperationException(String.Format("The parameter {0} already exists.", parameterName));
        }
        else
        {
            builder.Query = String.Concat(builder.Query.Substring(1), "&", parameterName, "=", value);
        }

        return builder.Query;
    }

gitorious.org/cadenza是我所见过的一些最有用的扩展方法的完整库。

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));
    }
}

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。

IEnumerable < >洗牌

我用Fisher-Yates算法实现了一个shuffle函数。

通过使用yield return和将代码分解为两个函数，它实现了适当的参数验证和延迟执行。(谢谢丹，在我的第一个版本中指出了这个缺陷)

static public IEnumerable<T> Shuffle<T>(this IEnumerable<T> source)
{
    if (source == null) throw new ArgumentNullException("source");

    return ShuffleIterator(source);
}

static private IEnumerable<T> ShuffleIterator<T>(this IEnumerable<T> source)
{
    T[] array = source.ToArray();
    Random rnd = new Random();          
    for (int n = array.Length; n > 1;)
    {
        int k = rnd.Next(n--); // 0 <= k < n

        //Swap items
        if (n != k)
        {
            T tmp = array[k];
            array[k] = array[n];
            array[n] = tmp;
        }
    }

    foreach (var item in array) yield return item;
}

我相信以前有人这样做过，但我发现自己经常使用这种方法(和更简单的导数):

public static bool CompareEx(this string strA, string strB, CultureInfo culture, bool ignoreCase)
{
    return string.Compare(strA, strB, ignoreCase, culture) == 0;
}

您可以以多种方式编写它，但我喜欢它，因为它非常快速地统一了比较字符串的方法，同时节省了代码行数(或代码字符)。