将任何字符串转换为类型Int32

// Calls the underlying int.TryParse method to convert a string
// representation of a number to its 32-bit signed integer equivalent.
// Returns Zero if conversion fails. 
public static int ToInt32(this string s)
{
    int retInt;
    int.TryParse(s, out retInt);
    return retInt;
}

示例使用: 字符串s = "999"; int i = s.ToInt32();

将字符串的长度减少到toLength，并在缩短的字符串的末尾添加一个额外的字符串，以表示字符串被缩短(默认值…)

public static string Shorten(this string str, int toLength, string cutOffReplacement = " ...")
{
    if (string.IsNullOrEmpty(str) || str.Length <= toLength)
        return str;
    else
        return str.Remove(toLength) + cutOffReplacement;
}

一些工具IEnumerable: ToString(格式)，ToString(函数)和Join(分隔符)。

例如:

var names = new[] { "Wagner", "Francine", "Arthur", "Bernardo" };

names.ToString("Name: {0}\n");
// Name: Wagner
// Name: Francine
// Name: Arthur
// Name: Bernardo

names.ToString(name => name.Length > 6 ? String.Format("{0} ", name) : String.Empty);
// Francine Bernardo

names.Join(" - ");
// Wagner - Francine - Arthur - Bernardo

扩展:

public static string ToString<T>(this IEnumerable<T> self, string format)
{
    return self.ToString(i => String.Format(format, i));
}

public static string ToString<T>(this IEnumerable<T> self, Func<T, object> function)
{
    var result = new StringBuilder();

    foreach (var item in self) result.Append(function(item));

    return result.ToString();
}

public static string Join<T>(this IEnumerable<T> self, string separator)
{
    return String.Join(separator, values: self.ToArray());
}

我已经实现了一个扩展方法包(在http://foop.codeplex.com/上可用)，其中一些是我日常使用的:

// the most beloved extension method for me is Pipe:
<%= variable.Pipe(x => this.SomeFunction(x)).Pipe(y =>
{
    ...;
    return this.SomeOtherFunction(y);
}) %>

var d = 28.December(2009); // some extension methods for creating DateTime
DateTime justDatePart = d.JustDate();
TimeSpan justTimePart = d.JustTime();
var nextTime = d.Add(5.Hours());

using(StreamReader reader = new StreamReader("lines-of-data-file-for-example")) {
    ...
    // for reading streams line by line and usable in LINQ
    var query = from line in reader.Lines(); 
                where line.Contains(_today)
                select new { Parts = PartsOf(line), Time = _now };
}

500.Sleep();

XmlSerialize and XmlDeserialize

IsNull and IsNotNull

IfTrue, IfFalse and Iff:
true.IfTrue(() => Console.WriteLine("it is true then!");

IfNull and IfNotNull

NullPartial用于ASP MVC的HTML helper。

当传递一个空模型时，HTML。Partial和HTML。RenderPartial将提供视图的模型，如果这个部分是强类型的，而视图有不同的类型，它将抛出一个异常，而不是传递一个空引用。这些帮助程序允许您指定两个不同的部分，这样您就可以将空测试排除在视图之外。

您有权在Codeplex页面上包含此内容

public static class nullpartials
    {
        public static MvcHtmlString NullPartial(this HtmlHelper helper, string Partial, string NullPartial, object Model)
        {
            if (Model == null)
                return helper.Partial(NullPartial);
            else
                return helper.Partial(Partial, Model);
        }

        public static MvcHtmlString NullPartial(this HtmlHelper helper, string Partial, string NullPartial, object Model, ViewDataDictionary viewdata)
        {
            if (Model == null)
                return helper.Partial(NullPartial, viewdata);
            else
                return helper.Partial(Partial, Model, viewdata);
        }

        public static void RenderNullPartial(this HtmlHelper helper, string Partial, string NullPartial, object Model)
        {
            if (Model == null)
            {
                helper.RenderPartial(NullPartial);
                return;
            }
            else
            {
                helper.RenderPartial(Partial, Model);
                return;
            }
        }

        public static void RenderNullPartial(this HtmlHelper helper, string Partial, string NullPartial, object Model, ViewDataDictionary viewdata)
        {
            if (Model == null)
            {
                helper.RenderPartial(NullPartial, viewdata);
                return;
            }
            else
            {
                helper.RenderPartial(Partial, Model, viewdata);
                return;
            }
        }
    }

您可能已经知道扩展方法的一个有趣用法是作为一种mixin。一些扩展方法，比如XmlSerializable，几乎污染了所有类;这对大多数人来说没有意义，比如Thread和SqlConnection。

一些功能应该显式地混合到希望拥有它的类中。我对这种类型提出了一种新的表示法，以M为前缀。

XmlSerializable是这样的:

public interface MXmlSerializable { }
public static class XmlSerializable {
  public static string ToXml(this MXmlSerializable self) {
    if (self == null) throw new ArgumentNullException();
    var serializer = new XmlSerializer(self.GetType());
    using (var writer = new StringWriter()) {
      serializer.Serialize(writer, self);
      return writer.GetStringBuilder().ToString();
    }
  }
  public static T FromXml<T>(string xml) where T : MXmlSerializable {
    var serializer = new XmlSerializer(typeof(T));
    return (T)serializer.Deserialize(new StringReader(xml));
  }
}

然后一个类将其混合:

public class Customer : MXmlSerializable {
  public string Name { get; set; }
  public bool Preferred { get; set; }
}

用法很简单:

var customer = new Customer { 
  Name = "Guybrush Threepwood", 
  Preferred = true };
var xml = customer.ToXml();

如果您喜欢这个想法，您可以在项目中为有用的mixin创建一个新的名称空间。你怎么看?

哦，顺便说一下，我认为大多数扩展方法都应该显式地测试null。