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。


当前回答

下面是一个扩展方法,它适应Rick Strahl的代码(以及注释),使您不必在每次将字节数组或文本文件转换为字符串时猜测或阅读其字节顺序标记。

这个代码片段允许你简单地做:

byte[] buffer = File.ReadAllBytes(@"C:\file.txt");
string content = buffer.GetString();

如果你发现任何错误,请添加到评论中。请随意将它包含在Codeplex项目中。

public static class Extensions
{
    /// <summary>
    /// Converts a byte array to a string, using its byte order mark to convert it to the right encoding.
    /// Original article: http://www.west-wind.com/WebLog/posts/197245.aspx
    /// </summary>
    /// <param name="buffer">An array of bytes to convert</param>
    /// <returns>The byte as a string.</returns>
    public static string GetString(this byte[] buffer)
    {
        if (buffer == null || buffer.Length == 0)
            return "";

        // Ansi as default
        Encoding encoding = Encoding.Default;       

        /*
            EF BB BF    UTF-8 
            FF FE UTF-16    little endian 
            FE FF UTF-16    big endian 
            FF FE 00 00 UTF-32, little endian 
            00 00 FE FF UTF-32, big-endian 
         */

        if (buffer[0] == 0xef && buffer[1] == 0xbb && buffer[2] == 0xbf)
            encoding = Encoding.UTF8;
        else if (buffer[0] == 0xfe && buffer[1] == 0xff)
            encoding = Encoding.Unicode;
        else if (buffer[0] == 0xfe && buffer[1] == 0xff)
            encoding = Encoding.BigEndianUnicode; // utf-16be
        else if (buffer[0] == 0 && buffer[1] == 0 && buffer[2] == 0xfe && buffer[3] == 0xff)
            encoding = Encoding.UTF32;
        else if (buffer[0] == 0x2b && buffer[1] == 0x2f && buffer[2] == 0x76)
            encoding = Encoding.UTF7;

        using (MemoryStream stream = new MemoryStream())
        {
            stream.Write(buffer, 0, buffer.Length);
            stream.Seek(0, SeekOrigin.Begin);
            using (StreamReader reader = new StreamReader(stream, encoding))
            {
                return reader.ReadToEnd();
            }
        }
    }
}

其他回答

避免参数的解析模式:

public static bool TryParseInt32(this string input, Action<int> action)
{
    int result;
    if (Int32.TryParse(input, out result))
    {
        action(result);
        return true;
    }
    return false;
}

用法:

if (!textBox.Text.TryParseInt32(number => label.Text = SomeMathFunction(number)))
    label.Text = "Please enter a valid integer";

这可以放在codeplex项目中,如果需要的话

这是罗马数字的to-and-from。不常用,但可能很方便。用法:

if ("IV".IsValidRomanNumeral())
{
   // Do useful stuff with the number 4.
}

Console.WriteLine("MMMDCCCLXXXVIII".ParseRomanNumeral());
Console.WriteLine(3888.ToRomanNumeralString());

源:

    public static class RomanNumeralExtensions
    {
        private const int NumberOfRomanNumeralMaps = 13;

        private static readonly Dictionary<string, int> romanNumerals =
            new Dictionary<string, int>(NumberOfRomanNumeralMaps)
            {
                { "M", 1000 }, 
                { "CM", 900 }, 
                { "D", 500 }, 
                { "CD", 400 }, 
                { "C", 100 }, 
                { "XC", 90 }, 
                { "L", 50 }, 
                { "XL", 40 }, 
                { "X", 10 }, 
                { "IX", 9 }, 
                { "V", 5 }, 
                { "IV", 4 }, 
                { "I", 1 }
            };

        private static readonly Regex validRomanNumeral = new Regex(
            "^(?i:(?=[MDCLXVI])((M{0,3})((C[DM])|(D?C{0,3}))"
            + "?((X[LC])|(L?XX{0,2})|L)?((I[VX])|(V?(II{0,2}))|V)?))$", 
            RegexOptions.Compiled);

        public static bool IsValidRomanNumeral(this string value)
        {
            return validRomanNumeral.IsMatch(value);
        }

        public static int ParseRomanNumeral(this string value)
        {
            if (value == null)
            {
                throw new ArgumentNullException("value");
            }

            value = value.ToUpperInvariant().Trim();

            var length = value.Length;

            if ((length == 0) || !value.IsValidRomanNumeral())
            {
                throw new ArgumentException("Empty or invalid Roman numeral string.", "value");
            }

            var total = 0;
            var i = length;

            while (i > 0)
            {
                var digit = romanNumerals[value[--i].ToString()];

                if (i > 0)
                {
                    var previousDigit = romanNumerals[value[i - 1].ToString()];

                    if (previousDigit < digit)
                    {
                        digit -= previousDigit;
                        i--;
                    }
                }

                total += digit;
            }

            return total;
        }

        public static string ToRomanNumeralString(this int value)
        {
            const int MinValue = 1;
            const int MaxValue = 3999;

            if ((value < MinValue) || (value > MaxValue))
            {
                throw new ArgumentOutOfRangeException("value", value, "Argument out of Roman numeral range.");
            }

            const int MaxRomanNumeralLength = 15;
            var sb = new StringBuilder(MaxRomanNumeralLength);

            foreach (var pair in romanNumerals)
            {
                while (value / pair.Value > 0)
                {
                    sb.Append(pair.Key);
                    value -= pair.Value;
                }
            }

            return sb.ToString();
        }
    }

轻松序列化对象为XML:

public static string ToXml<T>(this T obj) where T : class
{
    XmlSerializer s = new XmlSerializer(obj.GetType());
    using (StringWriter writer = new StringWriter())
    {
        s.Serialize(writer, obj);
        return writer.ToString();
    }
}

"<root><child>foo</child</root>".ToXml<MyCustomType>();

我有一个扩展方法记录异常:

public static void Log(this Exception obj)
{
  //your logging logic here
}

它的用法是这样的:

try
{
    //Your stuff here
}
catch(Exception ex)
{
    ex.Log();
}

[抱歉发了两次;第二个设计得更好:-)]

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