// Values ordered true/false
// True/false values separated by a capital letter
// Only two values allowed
// ---------------------------
// Limited, but could be useful
public enum BooleanFormat
{
    OneZero,
    YN,
    YesNo,
    TF,
    TrueFalse,
    PassFail,
    YepNope
}

public static class BooleanExtension
{
    /// <summary>
    /// Converts the boolean value of this instance to the specified string value. 
    /// </summary>
    private static string ToString(this bool value, string passValue, string failValue)
    {
        return value ? passValue : failValue;
    }

    /// <summary>
    /// Converts the boolean value of this instance to a string. 
    /// </summary>
    /// <param name="booleanFormat">A BooleanFormat value. 
    /// Example: BooleanFormat.PassFail would return "Pass" if true and "Fail" if false.</param>
    /// <returns>Boolean formatted string</returns>
    public static string ToString(this bool value, BooleanFormat booleanFormat)
    {
        string booleanFormatString = Enum.GetName(booleanFormat.GetType(), booleanFormat);
        return ParseBooleanString(value, booleanFormatString);      
    }

    // Parses boolean format strings, not optimized
    private static string ParseBooleanString(bool value, string booleanFormatString)
    {
        StringBuilder trueString = new StringBuilder();
        StringBuilder falseString = new StringBuilder();

        int charCount = booleanFormatString.Length;

        bool isTrueString = true;

        for (int i = 0; i != charCount; i++)
        {
            if (char.IsUpper(booleanFormatString[i]) && i != 0)
                isTrueString = false;

            if (isTrueString)
                trueString.Append(booleanFormatString[i]);
            else
                falseString.Append(booleanFormatString[i]);
        }

        return (value == true ? trueString.ToString() : falseString.ToString());
    }

我写过无数的扩展方法，这里有几个我觉得特别有用的。请随意执行。

public static class ControlExtenders
{
    /// <summary>
    /// Advanced version of find control.
    /// </summary>
    /// <typeparam name="T">Type of control to find.</typeparam>
    /// <param name="id">Control id to find.</param>
    /// <returns>Control of given type.</returns>
    /// <remarks>
    /// If the control with the given id is not found
    /// a new control instance of the given type is returned.
    /// </remarks>
    public static T FindControl<T>(this Control control, string id) where T : Control
    {
        // User normal FindControl method to get the control
        Control _control = control.FindControl(id);

        // If control was found and is of the correct type we return it
        if (_control != null && _control is T)
        {
            // Return new control
            return (T)_control;
        }

        // Create new control instance
        _control = (T)Activator.CreateInstance(typeof(T));

        // Add control to source control so the
        // next it is found and the value can be
        // passed on itd, remember to hide it and
        // set an ID so it can be found next time
        if (!(_control is ExtenderControlBase))
        {
            _control.Visible = false;
        }
        _control.ID = id;
        control.Controls.Add(_control);

        // Use reflection to create a new instance of the control
        return (T)_control;
    }
}

public static class GenericListExtenders
{
    /// <summary>
    /// Sorts a generic list by items properties.
    /// </summary>
    /// <typeparam name="T">Type of collection.</typeparam>
    /// <param name="list">Generic list.</param>
    /// <param name="fieldName">Field to sort data on.</param>
    /// <param name="sortDirection">Sort direction.</param>
    /// <remarks>
    /// Use this method when a dinamyc sort field is requiered. If the 
    /// sorting field is known manual sorting might improve performance.
    /// </remarks>
    public static void SortObjects<T>(this List<T> list, string fieldName, SortDirection sortDirection)
    {
        PropertyInfo propInfo = typeof(T).GetProperty(fieldName);
        if (propInfo != null)
        {
            Comparison<T> compare = delegate(T a, T b)
            {
                bool asc = sortDirection == SortDirection.Ascending;
                object valueA = asc ? propInfo.GetValue(a, null) : propInfo.GetValue(b, null);
                object valueB = asc ? propInfo.GetValue(b, null) : propInfo.GetValue(a, null);
                return valueA is IComparable ? ((IComparable)valueA).CompareTo(valueB) : 0;
            };
            list.Sort(compare);
        }
    }

    /// <summary>
    /// Creates a pagged collection from generic list.
    /// </summary>
    /// <typeparam name="T">Type of collection.</typeparam>
    /// <param name="list">Generic list.</param>
    /// <param name="sortField">Field to sort data on.</param>
    /// <param name="sortDirection">Sort direction.</param>
    /// <param name="from">Page from item index.</param>
    /// <param name="to">Page to item index.</param>
    /// <param name="copy">Creates a copy and returns a new list instead of changing the current one.</param>
    /// <returns>Pagged list collection.</returns>
    public static List<T> Page<T>(this List<T> list, string sortField, bool sortDirection, int from, int to, bool copy)
    {
        List<T> _pageList = new List<T>();

        // Copy list
        if (copy)
        {
            T[] _arrList = new T[list.Count];
            list.CopyTo(_arrList);
            _pageList = new List<T>(_arrList);
        }
        else
        {
            _pageList = list;
        }

        // Make sure there are enough items in the list
        if (from > _pageList.Count)
        {
            int diff = Math.Abs(from - to);
            from = _pageList.Count - diff;
        }
        if (to > _pageList.Count)
        {
            to = _pageList.Count;
        }

        // Sort items
        if (!string.IsNullOrEmpty(sortField))
        {
            SortDirection sortDir = SortDirection.Descending;
            if (!sortDirection) sortDir = SortDirection.Ascending;
            _pageList.SortObjects(sortField, sortDir);
        }

        // Calculate max number of items per page
        int count = to - from;
        if (from + count > _pageList.Count) count -= (from + count) - _pageList.Count;

        // Get max number of items per page
        T[] pagged = new T[count];
        _pageList.CopyTo(from, pagged, 0, count);

        // Return pagged items
        return new List<T>(pagged);
    }

    /// <summary>
    /// Shuffle's list items.
    /// </summary>
    /// <typeparam name="T">List type.</typeparam>
    /// <param name="list">Generic list.</param>
    public static void Shuffle<T>(this List<T> list)
    {
        Random rng = new Random();
        for (int i = list.Count - 1; i > 0; i--)
        {
            int swapIndex = rng.Next(i + 1);
            if (swapIndex != i)
            {
                T tmp = list[swapIndex];
                list[swapIndex] = list[i];
                list[i] = tmp;
            }
        }
    }

    /// <summary>
    /// Converts generic List to DataTable.
    /// </summary>
    /// <typeparam name="T">Type.</typeparam>
    /// <param name="list">Generic list.</param>
    /// <param name="columns">Name of the columns to copy to the DataTable.</param>
    /// <returns>DataTable.</returns>
    public static DataTable ToDataTable<T>(this List<T> list, string[] columns)
    {
        List<string> _columns = new List<string>(columns);
        DataTable dt = new DataTable();

        foreach (PropertyInfo info in typeof(T).GetProperties())
        {
            if (_columns.Contains(info.Name) || columns == null)
            {
                dt.Columns.Add(new DataColumn(info.Name, info.PropertyType));
            }
        }
        foreach (T t in list)
        {
            DataRow row = dt.NewRow();
            foreach (PropertyInfo info in typeof(T).GetProperties())
            {
                if (_columns.Contains(info.Name) || columns == null)
                {
                    row[info.Name] = info.GetValue(t, null);
                }
            }
            dt.Rows.Add(row);
        }
        return dt;
    }
}

public static class DateTimeExtenders
{
    /// <summary>
    /// Returns number of month from a string representation.
    /// </summary>
    /// <returns>Number of month.</returns>
    public static int MonthToNumber(this DateTime datetime, string month)
    {
        month = month.ToLower();
        for (int i = 1; i <= 12; i++)
        {
            DateTime _dt = DateTime.Parse("1." + i + ".2000");
            string _month = CultureInfo.InvariantCulture.DateTimeFormat.GetMonthName(i).ToLower();
            if (_month == month)
            {
                return i;
            }
        }
        return 0;
    }

    /// <summary>
    /// Returns month name from month number.
    /// </summary>
    /// <returns>Name of month.</returns>
    public static string MonthToName(this DateTime datetime, int month)
    {
        for (int i = 1; i <= 12; i++)
        {
            if (i == month)
            {
                return CultureInfo.InvariantCulture.DateTimeFormat.GetMonthName(i);
            }
        }
        return "";
    }
}

public static class ObjectExtender
{
    public static object CloneBinary<T>(this T originalObject)
    {
        using (var stream = new System.IO.MemoryStream())
        {
            BinaryFormatter binaryFormatter = new BinaryFormatter();
            binaryFormatter.Serialize(stream, originalObject);
            stream.Position = 0;
            return (T)binaryFormatter.Deserialize(stream);
        }
    }

    public static object CloneObject(this object obj)
    {
        using (MemoryStream memStream = new MemoryStream())
        {
            BinaryFormatter binaryFormatter = new BinaryFormatter(null, new StreamingContext(StreamingContextStates.Clone));
            binaryFormatter.Serialize(memStream, obj);
            memStream.Position = 0;
            return binaryFormatter.Deserialize(memStream);
        }
    }
}

public static class StringExtenders
{
    /// <summary>
    /// Returns string as unit.
    /// </summary>
    /// <param name="value">Value.</param>
    /// <returns>Unit</returns>
    public static Unit ToUnit(this string value)
    {
        // Return empty unit
        if (string.IsNullOrEmpty(value))
            return Unit.Empty;

        // Trim value
        value = value.Trim();

        // Return pixel unit
        if (value.EndsWith("px"))
        {
            // Set unit type
            string _int = value.Replace("px", "");

            // Try parsing to int
            double _val = 0;
            if (!double.TryParse(_int, out _val))
            {
                // Invalid value
                return Unit.Empty;
            }

            // Return unit
            return new Unit(_val, UnitType.Pixel);
        }

        // Return percent unit
        if (value.EndsWith("%"))
        {
            // Set unit type
            string _int = value.Replace("%", "");

            // Try parsing to int
            double _val = 0;
            if (!double.TryParse(_int, out _val))
            {
                // Invalid value
                return Unit.Empty;
            }

            // Return unit
            return new Unit(_val, UnitType.Percentage);
        }

        // No match found
        return new Unit();
    }

    /// <summary>
    /// Returns alternative string if current string is null or empty.
    /// </summary>
    /// <param name="str"></param>
    /// <param name="alternative"></param>
    /// <returns></returns>
    public static string Alternative(this string str, string alternative)
    {
        if (string.IsNullOrEmpty(str)) return alternative;
        return str;
    }

    /// <summary>
    /// Removes all HTML tags from string.
    /// </summary>
    /// <param name="html">String containing HTML tags.</param>
    /// <returns>String with no HTML tags.</returns>
    public static string StripHTML(this string html)
    {
        string nohtml = Regex.Replace(html, "<(.|\n)*?>", "");
        nohtml = nohtml.Replace("\r\n", "").Replace("\n", "").Replace("&nbsp;", "").Trim();
        return nohtml;
    }
}

第一个是我最喜欢的，因为它可以代替:

Control c = this.FindControl("tbName");
if (c != null)
{
    // Do something with c
    customer.Name = ((TextBox)c).Text;
}

用这个:

TextBox c = this.FindControl<TextBox>("tbName");
customer.Name = c.Text;

设置默认字符串值:

string str = "";
if (string.IsNullOrEmpty(str))
{
    str = "I'm empty!";
}

就变成:

str = str.Alternative("I'm empty!");

HTH。这些是我的一些主要问题。

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;

namespace Insert.Your.Namespace.Here.Helpers
{
    public static class Extensions
    {
        public static bool IsNullOrEmpty<T>(this IEnumerable<T> iEnumerable)
        {
            // Cheers to Joel Mueller for the bugfix. Was .Count(), now it's .Any()
            return iEnumerable == null ||
                   !iEnumerable.Any();
        }

        public static IList<T> ToListIfNotNullOrEmpty<T>(this IList<T> iList)
        {
            return iList.IsNullOrEmpty() ? null : iList;
        }

        public static PagedList<T> ToPagedListIfNotNullOrEmpty<T>(this PagedList<T> pagedList)
        {
            return pagedList.IsNullOrEmpty() ? null : pagedList;
        }

        public static string ToPluralString(this int value)
        {
            return value == 1 ? string.Empty : "s";
        }

        public static string ToReadableTime(this DateTime value)
        {
            TimeSpan span = DateTime.Now.Subtract(value);
            const string plural = "s";


            if (span.Days > 7)
            {
                return value.ToShortDateString();
            }

            switch (span.Days)
            {
                case 0:
                    switch (span.Hours)
                    {
                        case 0:
                            if (span.Minutes == 0)
                            {
                                return span.Seconds <= 0
                                           ? "now"
                                           : string.Format("{0} second{1} ago",
                                                           span.Seconds,
                                                           span.Seconds != 1 ? plural : string.Empty);
                            }
                            return string.Format("{0} minute{1} ago",
                                                 span.Minutes,
                                                 span.Minutes != 1 ? plural : string.Empty);
                        default:
                            return string.Format("{0} hour{1} ago",
                                                 span.Hours,
                                                 span.Hours != 1 ? plural : string.Empty);
                    }
                default:
                    return string.Format("{0} day{1} ago",
                                         span.Days,
                                         span.Days != 1 ? plural : string.Empty);
            }
        }

        public static string ToShortGuidString(this Guid value)
        {
            return Convert.ToBase64String(value.ToByteArray())
                .Replace("/", "_")
                .Replace("+", "-")
                .Substring(0, 22);
        }

        public static Guid FromShortGuidString(this string value)
        {
            return new Guid(Convert.FromBase64String(value.Replace("_", "/")
                                                         .Replace("-", "+") + "=="));
        }

        public static string ToStringMaximumLength(this string value, int maximumLength)
        {
            return ToStringMaximumLength(value, maximumLength, "...");
        }

        public static string ToStringMaximumLength(this string value, int maximumLength, string postFixText)
        {
            if (string.IsNullOrEmpty(postFixText))
            {
                throw new ArgumentNullException("postFixText");
            }

            return value.Length > maximumLength
                       ? string.Format(CultureInfo.InvariantCulture,
                                       "{0}{1}",
                                       value.Substring(0, maximumLength - postFixText.Length),
                                       postFixText)
                       :
                           value;
        }

        public static string SlugDecode(this string value)
        {
            return value.Replace("_", " ");
        }

        public static string SlugEncode(this string value)
        {
            return value.Replace(" ", "_");
        }
    }
}

public static class StringHelper
{
    public static String F(this String str, params object[] args)
    {
        return String.Format(str, args);
    }
}

使用:

"Say {0}".F("Hello");

我相信以前有人这样做过，但我发现自己经常使用这种方法(和更简单的导数):

public static bool CompareEx(this string strA, string strB, CultureInfo culture, bool ignoreCase)
{
    return string.Compare(strA, strB, ignoreCase, culture) == 0;
}

您可以以多种方式编写它，但我喜欢它，因为它非常快速地统一了比较字符串的方法，同时节省了代码行数(或代码字符)。

而与MVC工作，有很多if语句，我只关心或真或假，打印null，或字符串。在另一种情况下，我想到了:

public static TResult WhenTrue<TResult>(this Boolean value, Func<TResult> expression)
{
    return value ? expression() : default(TResult);
}

public static TResult WhenTrue<TResult>(this Boolean value, TResult content)
{
    return value ? content : default(TResult);
}

public static TResult WhenFalse<TResult>(this Boolean value, Func<TResult> expression)
{
    return !value ? expression() : default(TResult);
}

public static TResult WhenFalse<TResult>(this Boolean value, TResult content)
{
    return !value ? content : default(TResult);
}

它允许我改变<%= (someBool) ?print y:字符串。将%>空为<%= someBool。WhenTrue("print y") %>。

我只在我的视图中使用它，在这里我混合了代码和HTML，在代码文件中编写“更长的”版本更清楚。