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。
ASP。NET中,我使用这些扩展httpessionstate来加载会话中的对象。
它允许您以干净的方式加载会话对象,如果它们不存在,则将创建和初始化它们。
我使用两个扩展方法,如下所示:
private bool CreateMode;
private MyClass SomeClass;
protected override void OnInit (EventArgs e)
{
CreateMode = Session.GetSessionValue<bool> ("someKey1", () => true);
SomeClass = Session.GetSessionClass<MyClass> ("someKey2", () => new MyClass ()
{
MyProperty = 123
});
}
下面是扩展类:
public static class SessionExtensions
{
public delegate object UponCreate ();
public static T GetSessionClass<T> (this HttpSessionState session,
string key, UponCreate uponCreate) where T : class
{
if (null == session[key])
{
var item = uponCreate () as T;
session[key] = item;
return item;
}
return session[key] as T;
}
public static T GetSessionValue<T> (this HttpSessionState session,
string key, UponCreate uponCreate) where T : struct
{
if (null == session[key])
{
var item = uponCreate();
session[key] = item;
return (T)item;
}
return (T)session[key];
}
}
public static class StringExtensions {
/// <summary>
/// Parses a string into an Enum
/// </summary>
/// <typeparam name="T">The type of the Enum</typeparam>
/// <param name="value">String value to parse</param>
/// <returns>The Enum corresponding to the stringExtensions</returns>
public static T EnumParse<T>(this string value) {
return StringExtensions.EnumParse<T>(value, false);
}
public static T EnumParse<T>(this string value, bool ignorecase) {
if (value == null) {
throw new ArgumentNullException("value");
}
value = value.Trim();
if (value.Length == 0) {
throw new ArgumentException("Must specify valid information for parsing in the string.", "value");
}
Type t = typeof(T);
if (!t.IsEnum) {
throw new ArgumentException("Type provided must be an Enum.", "T");
}
return (T)Enum.Parse(t, value, ignorecase);
}
}
将字符串解析为Enum很有用。
public enum TestEnum
{
Bar,
Test
}
public class Test
{
public void Test()
{
TestEnum foo = "Test".EnumParse<TestEnum>();
}
}
这要归功于斯科特·多尔曼
——编辑Codeplex项目——
我问过Scott Dorman,他是否介意我们在Codeplex项目中发布他的代码。我从他那里得到的回答是:
感谢你对SO帖子和CodePlex项目的提醒。我赞成你对这个问题的回答。是的,代码目前在CodeProject开放许可证(http://www.codeproject.com/info/cpol10.aspx)下有效地处于公共领域。
我没有问题,这被包括在CodePlex项目,如果你想把我添加到项目(用户名是sdorman),我会添加该方法加上一些额外的枚举助手方法。
ASP。NET中,我使用这些扩展httpessionstate来加载会话中的对象。
它允许您以干净的方式加载会话对象,如果它们不存在,则将创建和初始化它们。
我使用两个扩展方法,如下所示:
private bool CreateMode;
private MyClass SomeClass;
protected override void OnInit (EventArgs e)
{
CreateMode = Session.GetSessionValue<bool> ("someKey1", () => true);
SomeClass = Session.GetSessionClass<MyClass> ("someKey2", () => new MyClass ()
{
MyProperty = 123
});
}
下面是扩展类:
public static class SessionExtensions
{
public delegate object UponCreate ();
public static T GetSessionClass<T> (this HttpSessionState session,
string key, UponCreate uponCreate) where T : class
{
if (null == session[key])
{
var item = uponCreate () as T;
session[key] = item;
return item;
}
return session[key] as T;
}
public static T GetSessionValue<T> (this HttpSessionState session,
string key, UponCreate uponCreate) where T : struct
{
if (null == session[key])
{
var item = uponCreate();
session[key] = item;
return (T)item;
}
return (T)session[key];
}
}
我使用以下扩展来扩展所有的集合(也许有人发现这些有用):
/// <summary>
/// Collection Helper
/// </summary>
/// <remarks>
/// Use IEnumerable by default, but when altering or getting item at index use IList.
/// </remarks>
public static class CollectionHelper
{
#region Alter;
/// <summary>
/// Swap item to another place
/// </summary>
/// <typeparam name="T">Collection type</typeparam>
/// <param name="this">Collection</param>
/// <param name="IndexA">Index a</param>
/// <param name="IndexB">Index b</param>
/// <returns>New collection</returns>
public static IList<T> Swap<T>(this IList<T> @this, Int32 IndexA, Int32 IndexB)
{
T Temp = @this[IndexA];
@this[IndexA] = @this[IndexB];
@this[IndexB] = Temp;
return @this;
}
/// <summary>
/// Swap item to the left
/// </summary>
/// <typeparam name="T">Collection type</typeparam>
/// <param name="this">Collection</param>
/// <param name="Index">Index</param>
/// <returns>New collection</returns>
public static IList<T> SwapLeft<T>(this IList<T> @this, Int32 Index)
{
return @this.Swap(Index, Index - 1);
}
/// <summary>
/// Swap item to the right
/// </summary>
/// <typeparam name="T">Collection type</typeparam>
/// <param name="this">Collection</param>
/// <param name="Index">Index</param>
/// <returns>New collection</returns>
public static IList<T> SwapRight<T>(this IList<T> @this, Int32 Index)
{
return @this.Swap(Index, Index + 1);
}
#endregion Alter;
#region Action;
/// <summary>
/// Execute action at specified index
/// </summary>
/// <typeparam name="T">Collection type</typeparam>
/// <param name="this">Collection</param>
/// <param name="Index">Index</param>
/// <param name="ActionAt">Action to execute</param>
/// <returns>New collection</returns>
public static IList<T> ActionAt<T>(this IList<T> @this, Int32 Index, Action<T> ActionAt)
{
ActionAt(@this[Index]);
return @this;
}
#endregion Action;
#region Randomize;
/// <summary>
/// Take random items
/// </summary>
/// <typeparam name="T">Collection type</typeparam>
/// <param name="this">Collection</param>
/// <param name="Count">Number of items to take</param>
/// <returns>New collection</returns>
public static IEnumerable<T> TakeRandom<T>(this IEnumerable<T> @this, Int32 Count)
{
return @this.Shuffle().Take(Count);
}
/// <summary>
/// Take random item
/// </summary>
/// <typeparam name="T">Collection type</typeparam>
/// <param name="this">Collection</param>
/// <returns>Item</returns>
public static T TakeRandom<T>(this IEnumerable<T> @this)
{
return @this.TakeRandom(1).Single();
}
/// <summary>
/// Shuffle list
/// </summary>
/// <typeparam name="T">Collection type</typeparam>
/// <param name="this">Collection</param>
/// <returns>New collection</returns>
public static IEnumerable<T> Shuffle<T>(this IEnumerable<T> @this)
{
return @this.OrderBy(Item => Guid.NewGuid());
}
#endregion Randomize;
#region Navigate;
/// <summary>
/// Get next item in collection and give first item, when last item is selected;
/// </summary>
/// <typeparam name="T">Collection type</typeparam>
/// <param name="this">Collection</param>
/// <param name="Index">Index in collection</param>
/// <returns>Next item</returns>
public static T Next<T>(this IList<T> @this, ref Int32 Index)
{
Index = ++Index >= 0 && Index < @this.Count ? Index : 0;
return @this[Index];
}
/// <summary>
/// Get previous item in collection and give last item, when first item is selected;
/// </summary>
/// <typeparam name="T">Collection type</typeparam>
/// <param name="this">Collection</param>
/// <param name="Index">Index in collection</param>
/// <returns>Previous item</returns>
public static T Previous<T>(this IList<T> @this, ref Int32 Index)
{
Index = --Index >= 0 && Index < @this.Count ? Index : @this.Count - 1;
return @this[Index];
}
#endregion Navigate;
#region Clone;
/// <summary>
///
/// </summary>
/// <typeparam name="T">Collection type</typeparam>
/// <param name="this">Collection</param>
/// <returns>Cloned collection</returns>
public static IEnumerable<T> Clone<T>(this IEnumerable<T> @this) where T : ICloneable
{
return @this.Select(Item => (T)Item.Clone());
}
#endregion Clone;
#region String;
/// <summary>
/// Joins multiple string with Separator
/// </summary>
/// <param name="this">Collection</param>
/// <param name="Separator">Separator</param>
/// <returns>Joined string</returns>
public static String Join(this IEnumerable<String> @this, String Separator = "")
{
return String.Join(Separator, @this);
}
#endregion String;
}
一些DataSet/DataRow扩展,使使用db结果更简单
只需在DataRow上使用. field ("fieldname"),如果可以,它将强制转换它,可选的默认值可以包括在内。
还有DataSet上的. hasrows(),这样你就不需要检查表和行的存在。
例子:
using (DataSet ds = yourcall())
{
if (ds.HasRows())
{
foreach (DataRow dr in ds.Tables[0].Rows)
{
int id = dr.Field<int>("ID");
string name = dr.Field<string>("Name");
string Action = dr.Field<string>("Action", "N/A");
}
}
}
代码:
using System;
using System.Data;
public static class DataSetExtensions
{
public static T Field<T>(this DataRow row, string columnName, T defaultValue)
{
try
{
return row.Field<T>(columnName);
}
catch
{
return defaultValue;
}
}
public static T Field<T>(this DataRow row, string columnName)
{
if (row[columnName] == null)
throw new NullReferenceException(columnName + " does not exist in DataRow");
string value = row[columnName].ToString();
if (typeof(T) == "".GetType())
{
return (T)Convert.ChangeType(value, typeof(T));
}
else if (typeof(T) == 0.GetType())
{
return (T)Convert.ChangeType(int.Parse(value), typeof(T));
}
else if (typeof(T) == false.GetType())
{
return (T)Convert.ChangeType(bool.Parse(value), typeof(T));
}
else if (typeof(T) == DateTime.Now.GetType())
{
return (T)Convert.ChangeType(DateTime.Parse(value), typeof(T));
}
else if (typeof(T) == new byte().GetType())
{
return (T)Convert.ChangeType(byte.Parse(value), typeof(T));
}
else if (typeof(T) == new float().GetType())
{
return (T)Convert.ChangeType(float.Parse(value), typeof(T));
}
else
{
throw new ArgumentException(string.Format("Cannot cast '{0}' to '{1}'.", value, typeof(T).ToString()));
}
}
public static bool HasRows(this DataSet dataSet)
{
return (dataSet.Tables.Count > 0 && dataSet.Tables[0].Rows.Count > 0);
}
}
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。