还有一点:

public enum ParseFailBehavior
{
   ReturnNull,
   ReturnDefault,
   ThrowException
}

public static T? ParseNullableEnum<T>(this string theValue, ParseFailBehavior desiredBehavior = ParseFailBehavior.ReturnNull) where T:struct
{
   T output;
   T? result = Enum.TryParse<T>(theValue, out output) 
      ? (T?)output
      : desiredBehavior == ParseFailBehavior.ReturnDefault
         ? (T?)default(T)
         : null;

   if(result == null && desiredBehavior == ParseFailBehavior.ThrowException)
      throw new ArgumentException("Parse Failed for value {0} of enum type {1}".
         FormatWith(theValue, typeof(T).Name));       
}

这个版本需要。net 4.0;在3.5中你没有TryParse和可选参数;你就只能使用enumel . parse()，你必须尝试捕获它。它在3.5中仍然是完全可行的(而且更有用，因为enumel . parse()是oogly的，也是你唯一的其他选择):

public static T? ParseNummableEnum<T>(this string theValue)
{
    return theValue.ParseNullableEnum<T>(ParseFailBehavior.ReturnNull);
}

public static T? ParseNullableEnum<T>(this string theValue, 
    ParseFailBehavior desiredBehavior) where T:struct
{
    try
    {
        return (T?) Enum.Parse(typeof (T), theValue);
    }
    catch (Exception)
    {
        if(desiredBehavior == ParseFailBehavior.ThrowException) throw;
    }

    return desiredBehavior == ParseFailBehavior.ReturnDefault ? (T?)default(T) : null;
}

用法:

//returns null if OptionOne isn't an enum constant
var myEnum = "OptionOne".ParseNullableEnum<OptionEnum>(); 

//guarantees a return value IF the enum has a "zero" constant value (generally a good practice)
var myEnum = "OptionTwo".ParseNullableEnum<OptionEnum>(ParseFailBehavior.ReturnDefault).Value 

每n个字符换行一个字符串。

public static string WrapAt(this string str, int WrapPos)
{
    if (string.IsNullOrEmpty(str))
        throw new ArgumentNullException("str", "Cannot wrap a null string");
    str = str.Replace("\r", "").Replace("\n", "");

    if (str.Length <= WrapPos)
        return str;

    for (int i = str.Length; i >= 0; i--)
        if (i % WrapPos == 0 && i > 0 && i != str.Length)
            str = str.Insert(i, "\r\n");
    return str;
}

……怎么样?

public static bool IsWinXPOrHigher(this OperatingSystem OS)
{
  return (OS.Platform == PlatformID.Win32NT)
    && ((OS.Version.Major > 5) || ((OS.Version.Major == 5) && (OS.Version.Minor >= 1)));
}

public static bool IsWinVistaOrHigher(this OperatingSystem OS)
{
  return (OS.Platform == PlatformID.Win32NT)
    && (OS.Version.Major >= 6);
}

public static bool IsWin7OrHigher(this OperatingSystem OS)
{
  return (OS.Platform == PlatformID.Win32NT)
    && ((OS.Version.Major > 6) || ((OS.Version.Major == 6) && (OS.Version.Minor >= 1)));
}

public static bool IsWin8OrHigher(this OperatingSystem OS)
{
  return (OS.Platform == PlatformID.Win32NT)
    && ((OS.Version.Major > 6) || ((OS.Version.Major == 6) && (OS.Version.Minor >= 2)));
}

用法:

if (Environment.OSVersion.IsWinXPOrHigher())
{
  // do stuff
}

if (Environment.OSVersion.IsWinVistaOrHigher())
{
  // do stuff
}

if (Environment.OSVersion.IsWin7OrHigher())
{
  // do stuff
}

if (Environment.OSVersion.IsWin8OrHigher())
{
  // do stuff
}

讨厌这种代码?

CloneableClass cc1 = new CloneableClass ();
CloneableClass cc2 = null;
CloneableClass cc3 = null;

cc3 = (CloneableClass) cc1.Clone (); // this is ok
cc3 = cc2.Clone (); // this throws null ref exception
// code to handle both cases
cc3 = cc1 != null ? (CloneableClass) cc1.Clone () : null;

它有点笨拙，所以我用这个扩展替换它，我称之为CloneOrNull -

public static T CloneOrNull<T> (this T self) where T : class, ICloneable
{
    if (self == null) return null;
    return (T) self.Clone ();
}

用法如下:

CloneableClass cc1 = new CloneableClass ();
CloneableClass cc2 = null;
CloneableClass cc3 = null;

cc3 = cc1.CloneOrNull (); // clone of cc1
cc3 = cc2.CloneOrNull (); // null
// look mom, no casts!

请随意在任何地方使用这个!

如果有Unix时间戳和ISO 8601格式的日期和时间就太好了。大量用于网站和休息服务。

我在我的Facebook图书馆里使用它。你可以找到源代码http://github.com/prabirshrestha/FacebookSharp/blob/master/src/FacebookSharp.Core/FacebookUtils/DateUtils.cs

private static readonly DateTime EPOCH = DateTime.SpecifyKind(new DateTime(1970, 1, 1, 0, 0, 0, 0),DateTimeKind.Utc);

public static DateTime FromUnixTimestamp(long timestamp)
{
    return EPOCH.AddSeconds(timestamp);
}

public static long ToUnixTimestamp(DateTime date)
{
    TimeSpan diff = date.ToUniversalTime() - EPOCH;
    return (long)diff.TotalSeconds;
}

public static DateTime FromIso8601FormattedDateTime(string iso8601DateTime){
    return DateTime.ParseExact(iso8601DateTime, "o", System.Globalization.CultureInfo.InvariantCulture);
}

public static string ToIso8601FormattedDateTime(DateTime dateTime)
{
    return dateTime.ToString("o");
}

请随意在codeplex项目中使用。

我经常用这个来表示可为空的数字。我帮助用0,NaN，无穷大…

public static bool IsNullOrDefault<T>(this T? o) 
    where T : struct
{
        return o == null || o.Value.Equals(default(T));
}