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。
Sql server有~2000个参数的限制,如果你有10k个id并想要与它们连接的记录,这是一个痛苦。我写了这些方法,接受批量id列表,并像这样调用:
List<Order> orders = dataContext.Orders.FetchByIds(
orderIdChunks,
list => row => list.Contains(row.OrderId)
);
List<Customer> customers = dataContext.Orders.FetchByIds(
orderIdChunks,
list => row => list.Contains(row.OrderId),
row => row.Customer
);
public static List<ResultType> FetchByIds<RecordType, ResultType>(
this IQueryable<RecordType> querySource,
List<List<int>> IdChunks,
Func<List<int>, Expression<Func<RecordType, bool>>> filterExpressionGenerator,
Expression<Func<RecordType, ResultType>> projectionExpression
) where RecordType : class
{
List<ResultType> result = new List<ResultType>();
foreach (List<int> chunk in IdChunks)
{
Expression<Func<RecordType, bool>> filterExpression =
filterExpressionGenerator(chunk);
IQueryable<ResultType> query = querySource
.Where(filterExpression)
.Select(projectionExpression);
List<ResultType> rows = query.ToList();
result.AddRange(rows);
}
return result;
}
public static List<RecordType> FetchByIds<RecordType>(
this IQueryable<RecordType> querySource,
List<List<int>> IdChunks,
Func<List<int>, Expression<Func<RecordType, bool>>> filterExpressionGenerator
) where RecordType : class
{
Expression<Func<RecordType, RecordType>> identity = r => r;
return FetchByIds(
querySource,
IdChunks,
filterExpressionGenerator,
identity
);
}
对于Winform控件:
/// <summary>
/// Returns whether the function is being executed during design time in Visual Studio.
/// </summary>
public static bool IsDesignTime(this Control control)
{
if (LicenseManager.UsageMode == LicenseUsageMode.Designtime)
{
return true;
}
if (control.Site != null && control.Site.DesignMode)
{
return true;
}
var parent = control.Parent;
while (parent != null)
{
if (parent.Site != null && parent.Site.DesignMode)
{
return true;
}
parent = parent.Parent;
}
return false;
}
/// <summary>
/// Sets the DropDownWidth to ensure that no item's text is cut off.
/// </summary>
public static void SetDropDownWidth(this ComboBox comboBox)
{
var g = comboBox.CreateGraphics();
var font = comboBox.Font;
float maxWidth = 0;
foreach (var item in comboBox.Items)
{
maxWidth = Math.Max(maxWidth, g.MeasureString(item.ToString(), font).Width);
}
if (comboBox.Items.Count > comboBox.MaxDropDownItems)
{
maxWidth += SystemInformation.VerticalScrollBarWidth;
}
comboBox.DropDownWidth = Math.Max(comboBox.Width, Convert.ToInt32(maxWidth));
}
IsDesignTime用法:
public class SomeForm : Form
{
public SomeForm()
{
InitializeComponent();
if (this.IsDesignTime())
{
return;
}
// Do something that makes the visual studio crash or hang if we're in design time,
// but any other time executes just fine
}
}
SetDropdownWidth用法:
ComboBox cbo = new ComboBox { Width = 50 };
cbo.Items.Add("Short");
cbo.Items.Add("A little longer");
cbo.Items.Add("Holy cow, this is a really, really long item. How in the world will it fit?");
cbo.SetDropDownWidth();
我忘了说,请随意在Codeplex上使用这些…
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];
}
}
如果有Unix时间戳和ISO 8601格式的日期和时间就太好了。大量用于网站和休息服务。
我在我的Facebook图书馆里使用它。你可以找到源代码http://github.com/prabirshrestha/FacebookSharp/blob/master/src/FacebookSharp.Core/FacebookUtils/DateUtils.cs
private static readonly DateTime EPOCH = DateTime.SpecifyKind(new DateTime(1970, 1, 1, 0, 0, 0, 0),DateTimeKind.Utc);
public static DateTime FromUnixTimestamp(long timestamp)
{
return EPOCH.AddSeconds(timestamp);
}
public static long ToUnixTimestamp(DateTime date)
{
TimeSpan diff = date.ToUniversalTime() - EPOCH;
return (long)diff.TotalSeconds;
}
public static DateTime FromIso8601FormattedDateTime(string iso8601DateTime){
return DateTime.ParseExact(iso8601DateTime, "o", System.Globalization.CultureInfo.InvariantCulture);
}
public static string ToIso8601FormattedDateTime(DateTime dateTime)
{
return dateTime.ToString("o");
}
请随意在codeplex项目中使用。