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。
WhereIf()方法
var query = dc.Reviewer
.Where(r => r.FacilityID == facilityID)
.WhereIf(CheckBoxActive.Checked, r => r.IsActive);
public static IEnumerable<TSource> WhereIf<TSource>(
this IEnumerable<TSource> source,
bool condition, Func<TSource, bool> predicate)
{
if (condition)
return source.Where(predicate);
else
return source;
}
public static IQueryable<TSource> WhereIf<TSource>(
this IQueryable<TSource> source,
bool condition, Expression<Func<TSource, bool>> predicate)
{
if (condition)
return source.Where(predicate);
else
return source;
}
我还为Where()扩展方法中的索引谓词添加了重载。为了更有趣,可以添加包含额外“else”谓词的风味。
获取一个camelCaseWord或PascalCaseWord并将其“Word化”,即camelCaseWord => camelCaseWord
public static string Wordify( this string camelCaseWord )
{
// if the word is all upper, just return it
if( !Regex.IsMatch( camelCaseWord, "[a-z]" ) )
return camelCaseWord;
return string.Join( " ", Regex.Split( camelCaseWord, @"(?<!^)(?=[A-Z])" ) );
}
我经常将它与大写字母结合使用
public static string Capitalize( this string word )
{
return word[0].ToString( ).ToUpper( ) + word.Substring( 1 );
}
示例使用
SomeEntityObject entity = DataAccessObject.GetSomeEntityObject( id );
List<PropertyInfo> properties = entity.GetType().GetPublicNonCollectionProperties( );
// wordify the property names to act as column headers for an html table or something
List<string> columns = properties.Select( p => p.Name.Capitalize( ).Wordify( ) ).ToList( );
在codeplex项目中免费使用
在序列化和配置上,最好使用长DateTime,因此:
public static readonly DateTime Epoch = new DateTime(1970, 1, 1, 0, 0, 0);
public static long ToUnixTimestamp(this DateTime dateTime)
{
return (long) (dateTime - Epoch).TotalSeconds;
}
public static long ToUnixUltraTimestamp(this DateTime dateTime)
{
return (long) (dateTime - Epoch).TotalMilliseconds;
}
和向后
public static DateTime ToDateTime(this long unixDateTime)
{
return Epoch.AddSeconds(unixDateTime);
}
public static DateTime ToDateTimeUltra(this long unixUltraDateTime)
{
return Epoch.AddMilliseconds(unixUltraDateTime);
}
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];
}
}
这些扩展方法异步调用事件。他们受到了StackOverflow的启发。
/// <summary>
/// Invoke an event asynchronously. Each subscriber to the event will be invoked on a separate thread.
/// </summary>
/// <param name="someEvent">The event to be invoked asynchronously.</param>
/// <param name="sender">The sender of the event.</param>
/// <param name="args">The args of the event.</param>
/// <typeparam name="TEventArgs">The type of <see cref="EventArgs"/> to be used with the event.</typeparam>
public static void InvokeAsync<TEventArgs>(this EventHandler<TEventArgs> someEvent, object sender, TEventArgs args)
where TEventArgs : EventArgs
{
if (someEvent == null)
{
return;
}
var eventListeners = someEvent.GetInvocationList();
AsyncCallback endAsyncCallback = delegate(IAsyncResult iar)
{
var ar = iar as AsyncResult;
if (ar == null)
{
return;
}
var invokedMethod = ar.AsyncDelegate as EventHandler<TEventArgs>;
if (invokedMethod != null)
{
invokedMethod.EndInvoke(iar);
}
};
foreach (EventHandler<TEventArgs> methodToInvoke in eventListeners)
{
methodToInvoke.BeginInvoke(sender, args, endAsyncCallback, null);
}
}
/// <summary>
/// Invoke an event asynchronously. Each subscriber to the event will be invoked on a separate thread.
/// </summary>
/// <param name="someEvent">The event to be invoked asynchronously.</param>
/// <param name="sender">The sender of the event.</param>
/// <param name="args">The args of the event.</param>
public static void InvokeAsync(this EventHandler someEvent, object sender, EventArgs args)
{
if (someEvent == null)
{
return;
}
var eventListeners = someEvent.GetInvocationList();
AsyncCallback endAsyncCallback = delegate(IAsyncResult iar)
{
var ar = iar as AsyncResult;
if (ar == null)
{
return;
}
var invokedMethod = ar.AsyncDelegate as EventHandler;
if (invokedMethod != null)
{
invokedMethod.EndInvoke(iar);
}
};
foreach (EventHandler methodToInvoke in eventListeners)
{
methodToInvoke.BeginInvoke(sender, args, endAsyncCallback, null);
}
}
使用方法:
public class Foo
{
public event EventHandler<EventArgs> Bar;
public void OnBar()
{
Bar.InvokeAsync(this, EventArgs.Empty);
}
}
请注意,在调用事件之前,您不必检查事件是否为空。例如:
EventHandler<EventArgs> handler = Bar;
if (handler != null)
{
// Invoke the event
}
测试:
void Main()
{
EventHandler<EventArgs> handler1 =
delegate(object sender, EventArgs args)
{
// Simulate performing work in handler1
Thread.Sleep(100);
Console.WriteLine("Handled 1");
};
EventHandler<EventArgs> handler2 =
delegate(object sender, EventArgs args)
{
// Simulate performing work in handler2
Thread.Sleep(50);
Console.WriteLine("Handled 2");
};
EventHandler<EventArgs> handler3 =
delegate(object sender, EventArgs args)
{
// Simulate performing work in handler3
Thread.Sleep(25);
Console.WriteLine("Handled 3");
};
var foo = new Foo();
foo.Bar += handler1;
foo.Bar += handler2;
foo.Bar += handler3;
foo.OnBar();
Console.WriteLine("Start executing important stuff");
// Simulate performing some important stuff here, where we don't want to
// wait around for the event handlers to finish executing
Thread.Sleep(1000);
Console.WriteLine("Finished executing important stuff");
}
调用事件将(通常)产生以下输出:
开始执行重要的事情
处理3
处理2
处理1
完成重要的任务
如果事件是同步调用的,它总是会产生这样的输出-并延迟“重要”内容的执行:
处理1
处理2
处理3
开始执行重要的事情
完成重要的任务