这一个是MVC，它添加了生成一个<label />标签到Html变量的能力，在每个ViewPage中可用。希望它能对其他试图开发类似扩展的人有所帮助。

Use:

<%= Html.Label("LabelId", "ForId", "Text")%>

输出:

<label id="LabelId" for="ForId">Text</label>

代码:

public static class HtmlHelperExtensions
{
    public static string Label(this HtmlHelper Html, string @for, string text)
    {
        return Html.Label(null, @for, text);
    }

    public static string Label(this HtmlHelper Html, string @for, string text, object htmlAttributes)
    {
        return Html.Label(null, @for, text, htmlAttributes);
    }

    public static string Label(this HtmlHelper Html, string @for, string text, IDictionary<string, object> htmlAttributes)
    {
        return Html.Label(null, @for, text, htmlAttributes);
    }

    public static string Label(this HtmlHelper Html, string id, string @for, string text)
    {
        return Html.Label(id, @for, text, null);
    }

    public static string Label(this HtmlHelper Html, string id, string @for, string text, object htmlAttributes)
    {
        return Html.Label(id, @for, text, new RouteValueDictionary(htmlAttributes));
    }

    public static string Label(this HtmlHelper Html, string id, string @for, string text, IDictionary<string, object> htmlAttributes)
    {
        TagBuilder tag = new TagBuilder("label");

        tag.MergeAttributes(htmlAttributes);

        if (!string.IsNullOrEmpty(id))
            tag.MergeAttribute("id", Html.AttributeEncode(id));

        tag.MergeAttribute("for", Html.AttributeEncode(@for));

        tag.SetInnerText(Html.Encode(text));

        return tag.ToString(TagRenderMode.Normal);
    }
}

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。

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));
    }
}

这些有用吗?

public static bool CoinToss(this Random rng)
{
    return rng.Next(2) == 0;
}

public static T OneOf<T>(this Random rng, params T[] things)
{
    return things[rng.Next(things.Length)];
}

Random rand;
bool luckyDay = rand.CoinToss();
string babyName = rand.OneOf("John", "George", "Radio XBR74 ROCKS!");

您可以从Random类中获得许多功能。

下面是我经常使用的一些扩展方法。有了这些，除了Next和NextDouble, Random类还提供了NextBool, NextChar, NextDateTime, NextTimeSpan, NextDouble(接受minValue和maxValue参数)，以及我个人最喜欢的NextString。还有更多(NextByte, NextShort, NextLong等);但这些主要是为了完整性，并不经常使用。所以我没有在这里包含它们(这段代码已经足够长了!)。

// todo: implement additional CharType values (e.g., AsciiAny)
public enum CharType {
    AlphabeticLower,
    AlphabeticUpper,
    AlphabeticAny,
    AlphanumericLower,
    AlphanumericUpper,
    AlphanumericAny,
    Numeric
}

public static class RandomExtensions {
    // 10 digits vs. 52 alphabetic characters (upper & lower);
    // probability of being numeric: 10 / 62 = 0.1612903225806452
    private const double AlphanumericProbabilityNumericAny = 10.0 / 62.0;

    // 10 digits vs. 26 alphabetic characters (upper OR lower);
    // probability of being numeric: 10 / 36 = 0.2777777777777778
    private const double AlphanumericProbabilityNumericCased = 10.0 / 36.0;

    public static bool NextBool(this Random random, double probability) {
        return random.NextDouble() <= probability;
    }

    public static bool NextBool(this Random random) {
        return random.NextDouble() <= 0.5;
    }

    public static char NextChar(this Random random, CharType mode) {
        switch (mode) {
            case CharType.AlphabeticAny:
                return random.NextAlphabeticChar();
            case CharType.AlphabeticLower:
                return random.NextAlphabeticChar(false);
            case CharType.AlphabeticUpper:
                return random.NextAlphabeticChar(true);
            case CharType.AlphanumericAny:
                return random.NextAlphanumericChar();
            case CharType.AlphanumericLower:
                return random.NextAlphanumericChar(false);
            case CharType.AlphanumericUpper:
                return random.NextAlphanumericChar(true);
            case CharType.Numeric:
                return random.NextNumericChar();
            default:
                return random.NextAlphanumericChar();
        }
    }

    public static char NextChar(this Random random) {
        return random.NextChar(CharType.AlphanumericAny);
    }

    private static char NextAlphanumericChar(this Random random, bool uppercase) {
        bool numeric = random.NextBool(AlphanumericProbabilityNumericCased);

        if (numeric)
            return random.NextNumericChar();
        else
            return random.NextAlphabeticChar(uppercase);
    }

    private static char NextAlphanumericChar(this Random random) {
        bool numeric = random.NextBool(AlphanumericProbabilityNumericAny);

        if (numeric)
            return random.NextNumericChar();
        else
            return random.NextAlphabeticChar(random.NextBool());
    }

    private static char NextAlphabeticChar(this Random random, bool uppercase) {
        if (uppercase)
            return (char)random.Next(65, 91);
        else
            return (char)random.Next(97, 123);
    }

    private static char NextAlphabeticChar(this Random random) {
        return random.NextAlphabeticChar(random.NextBool());
    }

    private static char NextNumericChar(this Random random) {
        return (char)random.Next(48, 58);
    }

    public static DateTime NextDateTime(this Random random, DateTime minValue, DateTime maxValue) {
        return DateTime.FromOADate(
            random.NextDouble(minValue.ToOADate(), maxValue.ToOADate())
        );
    }

    public static DateTime NextDateTime(this Random random) {
        return random.NextDateTime(DateTime.MinValue, DateTime.MaxValue);
    }

    public static double NextDouble(this Random random, double minValue, double maxValue) {
        if (maxValue < minValue)
            throw new ArgumentException("Minimum value must be less than maximum value.");

        double difference = maxValue - minValue;
        if (!double.IsInfinity(difference))
            return minValue + (random.NextDouble() * difference);

        else {
            // to avoid evaluating to Double.Infinity, we split the range into two halves:
            double halfDifference = (maxValue * 0.5) - (minValue * 0.5);

            // 50/50 chance of returning a value from the first or second half of the range
            if (random.NextBool())
                return minValue + (random.NextDouble() * halfDifference);
            else
                return (minValue + halfDifference) + (random.NextDouble() * halfDifference);
        }
    }

    public static string NextString(this Random random, int numChars, CharType mode) {
        char[] chars = new char[numChars];

        for (int i = 0; i < numChars; ++i)
            chars[i] = random.NextChar(mode);

        return new string(chars);
    }

    public static string NextString(this Random random, int numChars) {
        return random.NextString(numChars, CharType.AlphanumericAny);
    }

    public static TimeSpan NextTimeSpan(this Random random, TimeSpan minValue, TimeSpan maxValue) {
        return TimeSpan.FromMilliseconds(
            random.NextDouble(minValue.TotalMilliseconds, maxValue.TotalMilliseconds)
        );
    }

    public static TimeSpan NextTimeSpan(this Random random) {
        return random.NextTimeSpan(TimeSpan.MinValue, TimeSpan.MaxValue);
    }
}

我经常用这个…

原始代码:

if (guid != Guid.Empty) return guid;
else return Guid.NewGuid();

新代码:

return guid.NewGuidIfEmpty();

扩展方法:

public static Guid NewGuidIfEmpty(this Guid uuid)
{
    return (uuid != Guid.Empty ? uuid : Guid.NewGuid());
}