二分查找:

public static T BinarySearch<T, TKey>(this IList<T> list, Func<T, TKey> keySelector, TKey key)
        where TKey : IComparable<TKey>
{
    int min = 0;
    int max = list.Count;
    int index = 0;
    while (min < max)
    {
        int mid = (max + min) / 2;
        T midItem = list[mid];
        TKey midKey = keySelector(midItem);
        int comp = midKey.CompareTo(key);
        if (comp < 0)
        {
            min = mid + 1;
        }
        else if (comp > 0)
        {
            max = mid - 1;
        }
        else
        {
            return midItem;
        }
    }
    if (min == max &&
        keySelector(list[min]).CompareTo(key) == 0)
    {
        return list[min];
    }
    throw new InvalidOperationException("Item not found");
}

用法(假设列表按Id排序):

var item = list.BinarySearch(i => i.Id, 42);

它抛出InvalidOperationException的事实可能看起来很奇怪，但这就是Enumerable。第一种情况是没有匹配项。

另一个对我有用的是:

/// <summary>
/// Converts any type in to an Int32
/// </summary>
/// <typeparam name="T">Any Object</typeparam>
/// <param name="value">Value to convert</param>
/// <returns>The integer, 0 if unsuccessful</returns>
public static int ToInt32<T>(this T value)
{
  int result;
  if (int.TryParse(value.ToString(), out result))
  {
    return result;
  }
  return 0;
}

/// <summary>
/// Converts any type in to an Int32 but if null then returns the default
/// </summary>
/// <param name="value">Value to convert</param>
/// <typeparam name="T">Any Object</typeparam>
/// <param name="defaultValue">Default to use</param>
/// <returns>The defaultValue if unsuccessful</returns>
public static int ToInt32<T>(this T value, int defaultValue)
{
  int result;
  if (int.TryParse(value.ToString(), out result))
  {
    return result;
  }
  return defaultValue;
}

例子:

int number = "123".ToInt32();

or:

int badNumber = "a".ToInt32(100); // Returns 100 since a is nan

static string Format( this string str,
                    , params Expression<Func<string,object>>[] args)
{
    var parameters = args.ToDictionary
                        ( e=>string.Format("{{{0}}}",e.Parameters[0].Name)
                        , e=>e.Compile()(e.Parameters[0].Name));

    var sb = new StringBuilder(str);
    foreach(var kv in parameters)
    {
        sb.Replace( kv.Key
                  , kv.Value != null ? kv.Value.ToString() : "");
    }

    return sb.ToString();
}

有了上面的扩展，你可以这样写:

var str = "{foo} {bar} {baz}".Format(foo=>foo, bar=>2, baz=>new object());

你会得到"foo 2 System.Object"。

没有检查整个线程，所以它可能已经在这里，但是:

public static class FluentOrderingExtensions
    public class FluentOrderer<T> : IEnumerable<T>
    {
        internal List<Comparison<T>> Comparers = new List<Comparison<T>>();

        internal IEnumerable<T> Source;

        public FluentOrderer(IEnumerable<T> source)
        {
            Source = source;
        }

        #region Implementation of IEnumerable

        public IEnumerator<T> GetEnumerator()
        {
            var workingArray = Source.ToArray();
            Array.Sort(workingArray, IterativeComparison);

            foreach(var element in workingArray) yield return element;
        }

        private int IterativeComparison(T a, T b)
        {
            foreach (var comparer in Comparers)
            {
                var result = comparer(a,b);
                if(result != 0) return result;
            }
            return 0;
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }

        #endregion
    }

    public static FluentOrderer<T> OrderFluentlyBy<T,TResult>(this IEnumerable<T> source, Func<T,TResult> predicate) 
        where TResult : IComparable<TResult>
    {
        var result = new FluentOrderer<T>(source);
        result.Comparers.Add((a,b)=>predicate(a).CompareTo(predicate(b)));
        return result;
    }

    public static FluentOrderer<T> OrderFluentlyByDescending<T,TResult>(this IEnumerable<T> source, Func<T,TResult> predicate) 
        where TResult : IComparable<TResult>
    {
        var result = new FluentOrderer<T>(source);
        result.Comparers.Add((a,b)=>predicate(a).CompareTo(predicate(b)) * -1);
        return result;
    }

    public static FluentOrderer<T> ThenBy<T, TResult>(this FluentOrderer<T> source, Func<T, TResult> predicate)
        where TResult : IComparable<TResult>
    {
        source.Comparers.Add((a, b) => predicate(a).CompareTo(predicate(b)));
        return source;
    }

    public static FluentOrderer<T> ThenByDescending<T, TResult>(this FluentOrderer<T> source, Func<T, TResult> predicate)
        where TResult : IComparable<TResult>
    {
        source.Comparers.Add((a, b) => predicate(a).CompareTo(predicate(b)) * -1);
        return source;
    }
}

用法:

var myFluentlyOrderedList = GetABunchOfComplexObjects()
    .OrderFluentlyBy(x=>x.PropertyA)
    .ThenByDescending(x=>x.PropertyB)
    .ThenBy(x=>x.SomeMethod())
    .ThenBy(x=>SomeOtherMethodAppliedTo(x))
    .ToList();

．.． 当然，假设所有的谓词都返回与自身icomcomparable的类型。如果使用像MergeSort这样的稳定排序，而不是。net内置的快速排序，它会更好地工作，但它提供了类似于SQL的可读多字段排序能力(无论如何，它是方法链所能获得的最接近的功能)。您可以通过定义重载来接受比较lambda，而不是基于谓词创建它，从而扩展它以容纳非IComparable的成员。

EDIT: A little explanation, since the commenter got some upticks: this set of methods improves upon the basic OrderBy() functionality by allowing you to sort based on multiple fields in descending order of importance. A real-world example would be sorting a list of invoices by customer, then by invoice number (or invoice date). Other methods of getting the data in this order either wouldn't work (OrderBy() uses an unstable sort, so it cannot be chained) or would be inefficient and not look like it does what you're trying to do.

我喜欢这些NUnit Assert扩展:http://svn.caffeine-it.com/openrasta/trunk/src/Rasta.Testing/AssertExtensions.cs

通配符字符串比较:

public static bool MatchesWildcard(this string text, string pattern)
{
    int it = 0;
    while (text.CharAt(it) != 0 &&
           pattern.CharAt(it) != '*')
    {
        if (pattern.CharAt(it) != text.CharAt(it) && pattern.CharAt(it) != '?')
            return false;
        it++;
    }

    int cp = 0;
    int mp = 0;
    int ip = it;

    while (text.CharAt(it) != 0)
    {
        if (pattern.CharAt(ip) == '*')
        {
            if (pattern.CharAt(++ip) == 0)
                return true;
            mp = ip;
            cp = it + 1;
        }
        else if (pattern.CharAt(ip) == text.CharAt(it) || pattern.CharAt(ip) == '?')
        {
            ip++;
            it++;
        }
        else
        {
            ip = mp;
            it = cp++;
        }
    }

    while (pattern.CharAt(ip) == '*')
    {
        ip++;
    }
    return pattern.CharAt(ip) == 0;
}

public static char CharAt(this string s, int index)
{
    if (index < s.Length)
        return s[index];
    return '\0';
}

它直接翻译了本文中的C代码，因此CharAt方法将字符串的末尾返回0

if (fileName.MatchesWildcard("*.cs"))
{
    Console.WriteLine("{0} is a C# source file", fileName);
}