if(reallyLongIntegerVariableName.In(1,6,9,11))
{
// do something....
}
and
if(reallyLongStringVariableName.In("string1","string2","string3"))
{
// do something....
}
and
if(reallyLongMethodParameterName.In(SomeEnum.Value1, SomeEnum.Value2, SomeEnum.Value3, SomeEnum.Value4)
{
// do something....
}
s = "Hello {0} world {1}!".Fmt("Stack", "Overflow");
s = "Hello {0} world {1}!".FormatBy("Stack", "Overflow");
s = "Hello {0} world {1}!".FormatWith("Stack", "Overflow");
s = "Hello {0} world {1}!".Display("Stack", "Overflow");
s = "Hello {0} world {1}!".With("Stack", "Overflow");
public static class ComparableExtensions
{
public static bool Between(this T actual, T lower, T upper) where T : IComparable
{
return actual.CompareTo(lower) >= 0 && actual.CompareTo(upper) < 0;
}
}
public static void AddRange(this ICollection list, params S[] values)
where S : T
{
foreach (S value in values)
list.Add(value);
}
该方法适用于所有类型,并允许您将一系列项目作为参数添加到列表中.
例:
var list = new List();
list.AddRange(5, 4, 8, 4, 2);
只需使用collection initializer =>`var list = new List {5,4,8,4,2};` 这个IList 会更好 @Will:实际上,接受一个`ICollection `是最好的*; 那么它也可以用于,例如,`LinkedList `和`HashSet `,而不仅仅是索引集合. 在pre -.net 4.0中编辑[允许协方差](http://stackoverflow.com/questions/1995113/strangest-language-feature/2004371#2004371)
7> TWith2Sugars..：
一定要把它放在codeplex项目中.
将对象序列化/反序列化为XML:
/// Serializes an object of type T in to an xml string
/// Any class type
/// Object to serialize
/// A string that represents Xml, empty otherwise
public static string XmlSerialize(this T obj) where T : class, new()
{
if (obj == null) throw new ArgumentNullException("obj");
var serializer = new XmlSerializer(typeof(T));
using (var writer = new StringWriter())
{
serializer.Serialize(writer, obj);
return writer.ToString();
}
}
/// Deserializes an xml string in to an object of Type T
/// Any class type
/// Xml as string to deserialize from
/// A new object of type T is successful, null if failed
public static T XmlDeserialize(this string xml) where T : class, new()
{
if (xml == null) throw new ArgumentNullException("xml");
var serializer = new XmlSerializer(typeof(T));
using (var reader = new StringReader(xml))
{
try { return (T)serializer.Deserialize(reader); }
catch { return null; } // Could not be deserialized to this type.
}
}
public static class FrameworkExtensions
{
// a map function
public static void ForEach(this IEnumerable @enum, Action mapFunction)
{
foreach (var item in @enum) mapFunction(item);
}
}
天真的例子:
var buttons = GetListOfButtons() as IEnumerable
很酷的例子:
// no need to type the same assignment 3 times, just
// new[] up an array and use foreach + lambda
// everything is properly inferred by csc :-)
new { itemA, itemB, itemC }
.ForEach(item => {
item.Number = 1;
item.Str = "Hello World!";
});
int i = myString.To();
string a = myInt.ToOrDefault();
//note type inference
DateTime d = myString.ToOrOther(DateTime.MAX_VALUE);
double d;
//note type inference
bool didItGiveDefault = myString.ToOrDefault(out d);
string s = myDateTime.ToOrNull();
我无法让Nullable类型非常干净地滚动到整个事物中.在我扔掉毛巾之前,我试了大约20分钟.
就个人而言,我不是尝试/捕获确定结果的代码的粉丝.对于在预期逻辑IMO之外发生的错误,应该使用try/catch.hmmmmm 您至少应该更改"catch"子句,以便仅捕获ChangeType()在无法"转换"引用时将引发的异常.我想你不希望任何OutOfMemoryException,ExecutionEngineException,ThreadAbortException或类似的被视为转换错误.否则,这些事情很难跟踪错误. 我相信`ToOrNull`与`ToOrDefault`具有完全相同的行为(即,如果你在转换失败的引用类型上调用`ToOrDefault`,它将返回`null`).但更重要的是,它对我来说似乎有点多余,因为`var s = myObject as string`完成与`var s = myObject.ToOrNull ()`相同的事情 - 但是没有必要捕获`InvalidCastException` .我错过了什么吗？
10> 小智..：
我有一个记录异常的扩展方法:
public static void Log(this Exception obj)
{
//your logging logic here
}
public static class StringExtensions {
///
/// Parses a string into an Enum
///
/// The type of the Enum
/// String value to parse
/// The Enum corresponding to the stringExtensions
public static T EnumParse(this string value) {
return StringExtensions.EnumParse(value, false);
}
public static T EnumParse(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);
}
}
用于将字符串解析为枚举.
public enum TestEnum
{
Bar,
Test
}
public class Test
{
public void Test()
{
TestEnum foo = "Test".EnumParse();
}
}
public static string ToTitleCase(this string mText)
{
if (mText == null) return mText;
System.Globalization.CultureInfo cultureInfo = System.Threading.Thread.CurrentThread.CurrentCulture;
System.Globalization.TextInfo textInfo = cultureInfo.TextInfo;
// TextInfo.ToTitleCase only operates on the string if is all lower case, otherwise it returns the string unchanged.
return textInfo.ToTitleCase(mText.ToLower());
}
16> Jesse C. Sli..：
这是罗马数字的来往.不经常使用,但可能很方便.用法:
if ("IV".IsValidRomanNumeral())
{
// Do useful stuff with the number 4.
}
Console.WriteLine("MMMDCCCLXXXVIII".ParseRomanNumeral());
Console.WriteLine(3888.ToRomanNumeralString());
来源:
public static class RomanNumeralExtensions
{
private const int NumberOfRomanNumeralMaps = 13;
private static readonly Dictionary romanNumerals =
new Dictionary(NumberOfRomanNumeralMaps)
{
{ "M", 1000 },
{ "CM", 900 },
{ "D", 500 },
{ "CD", 400 },
{ "C", 100 },
{ "XC", 90 },
{ "L", 50 },
{ "XL", 40 },
{ "X", 10 },
{ "IX", 9 },
{ "V", 5 },
{ "IV", 4 },
{ "I", 1 }
};
private static readonly Regex validRomanNumeral = new Regex(
"^(?i:(?=[MDCLXVI])((M{0,3})((C[DM])|(D?C{0,3}))"
+ "?((X[LC])|(L?XX{0,2})|L)?((I[VX])|(V?(II{0,2}))|V)?))$",
RegexOptions.Compiled);
public static bool IsValidRomanNumeral(this string value)
{
return validRomanNumeral.IsMatch(value);
}
public static int ParseRomanNumeral(this string value)
{
if (value == null)
{
throw new ArgumentNullException("value");
}
value = value.ToUpperInvariant().Trim();
var length = value.Length;
if ((length == 0) || !value.IsValidRomanNumeral())
{
throw new ArgumentException("Empty or invalid Roman numeral string.", "value");
}
var total = 0;
var i = length;
while (i > 0)
{
var digit = romanNumerals[value[--i].ToString()];
if (i > 0)
{
var previousDigit = romanNumerals[value[i - 1].ToString()];
if (previousDigit < digit)
{
digit -= previousDigit;
i--;
}
}
total += digit;
}
return total;
}
public static string ToRomanNumeralString(this int value)
{
const int MinValue = 1;
const int MaxValue = 3999;
if ((value < MinValue) || (value > MaxValue))
{
throw new ArgumentOutOfRangeException("value", value, "Argument out of Roman numeral range.");
}
const int MaxRomanNumeralLength = 15;
var sb = new StringBuilder(MaxRomanNumeralLength);
foreach (var pair in romanNumerals)
{
while (value / pair.Value > 0)
{
sb.Append(pair.Key);
value -= pair.Value;
}
}
return sb.ToString();
}
}
17> Paolo Tedesc..：
处理尺寸的便捷方式:
public static class Extensions {
public static int K(this int value) {
return value * 1024;
}
public static int M(this int value) {
return value * 1024 * 1024;
}
}
public class Program {
public void Main() {
WSHttpContextBinding serviceMultipleTokenBinding = new WSHttpContextBinding() {
MaxBufferPoolSize = 2.M(), // instead of 2097152
MaxReceivedMessageSize = 64.K(), // instead of 65536
};
}
}
18> fre0n..：
对于Winform控件:
///
/// Returns whether the function is being executed during design time in Visual Studio.
///
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;
}
///
/// Sets the DropDownWidth to ensure that no item's text is cut off.
///
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();
我忘了提及,随意在Codeplex上使用这些...
19> bovium..：
ThrowIfArgumentIsNull是一个很好的方法来做我们都应该做的空检查.
public static class Extensions
{
public static void ThrowIfArgumentIsNull(this T obj, string parameterName) where T : class
{
if (obj == null) throw new ArgumentNullException(parameterName + " not allowed to be null");
}
}
下面是使用它的方法,它适用于命名空间中的所有类或在其中使用命名空间的任何位置.
internal class Test
{
public Test(string input1)
{
input1.ThrowIfArgumentIsNull("input1");
}
}
采用camelCaseWord或PascalCaseWord并将其"字形化",即camelCaseWord => camel Case Word
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, @"(?
我经常将它与Capitalize结合使用
public static string Capitalize( this string word )
{
return word[0].ToString( ).ToUpper( ) + word.Substring( 1 );
}
用法示例
SomeEntityObject entity = DataAccessObject.GetSomeEntityObject( id );
List properties = entity.GetType().GetPublicNonCollectionProperties( );
// wordify the property names to act as column headers for an html table or something
List columns = properties.Select( p => p.Name.Capitalize( ).Wordify( ) ).ToList( );
public static class Extensions
{
///
/// Converts a byte array to a string, using its byte order mark to convert it to the right encoding.
/// Original article: http://www.west-wind.com/WebLog/posts/197245.aspx
///
/// An array of bytes to convert
/// The byte as a string.
public static string GetString(this byte[] buffer)
{
if (buffer == null || buffer.Length == 0)
return "";
// Ansi as default
Encoding encoding = Encoding.Default;
/*
EF BB BF UTF-8
FF FE UTF-16 little endian
FE FF UTF-16 big endian
FF FE 00 00 UTF-32, little endian
00 00 FE FF UTF-32, big-endian
*/
if (buffer[0] == 0xef && buffer[1] == 0xbb && buffer[2] == 0xbf)
encoding = Encoding.UTF8;
else if (buffer[0] == 0xfe && buffer[1] == 0xff)
encoding = Encoding.Unicode;
else if (buffer[0] == 0xfe && buffer[1] == 0xff)
encoding = Encoding.BigEndianUnicode; // utf-16be
else if (buffer[0] == 0 && buffer[1] == 0 && buffer[2] == 0xfe && buffer[3] == 0xff)
encoding = Encoding.UTF32;
else if (buffer[0] == 0x2b && buffer[1] == 0x2f && buffer[2] == 0x76)
encoding = Encoding.UTF7;
using (MemoryStream stream = new MemoryStream())
{
stream.Write(buffer, 0, buffer.Length);
stream.Seek(0, SeekOrigin.Begin);
using (StreamReader reader = new StreamReader(stream, encoding))
{
return reader.ReadToEnd();
}
}
}
}
25> scobi..：
这是我今天刚刚创建的.
// requires .NET 4
public static TReturn NullOr(this TIn obj, Func func,
TReturn elseValue = default(TReturn)) where TIn : class
{ return obj != null ? func(obj) : elseValue; }
// versions for CLR 2, which doesn't support optional params
public static TReturn NullOr(this TIn obj, Func func,
TReturn elseValue) where TIn : class
{ return obj != null ? func(obj) : elseValue; }
public static TReturn NullOr(this TIn obj, Func func)
where TIn : class
{ return obj != null ? func(obj) : default(TReturn); }
它可以让你这样做:
var lname = thingy.NullOr(t => t.Name).NullOr(n => n.ToLower());
///
/// Creates an instance for the given
/// delegate function.
///
internal class ComparerFactory : IComparer
{
public static IComparer Create(Func comparison)
{
return new ComparerFactory(comparison);
}
private readonly Func _comparison;
private ComparerFactory(Func comparison)
{
_comparison = comparison;
}
#region IComparer Members
public int Compare(T x, T y)
{
return _comparison(x, y);
}
#endregion
}
...并且这些扩展方法在枚举上公开了我的新OrderBy重载.我怀疑它适用于LINQ to SQL,但它对于LINQ to Objects非常有用.
public static class EnumerableExtensions
{
///
/// Sorts the elements of a sequence in ascending order by using a specified comparison delegate.
///
public static IOrderedEnumerable OrderBy(this IEnumerable source, Func keySelector,
Func comparison)
{
var comparer = ComparerFactory.Create(comparison);
return source.OrderBy(keySelector, comparer);
}
///
/// Sorts the elements of a sequence in descending order by using a specified comparison delegate.
///
public static IOrderedEnumerable OrderByDescending(this IEnumerable source, Func keySelector,
Func comparison)
{
var comparer = ComparerFactory.Create(comparison);
return source.OrderByDescending(keySelector, comparer);
}
}
public static class StringEntentions {
///
/// Indicates whether the current string matches the supplied wildcard pattern. Behaves the same
/// as VB's "Like" Operator.
///
/// The string instance where the extension method is called
/// The wildcard pattern to match. Syntax matches VB's Like operator.
/// true if the string matches the supplied pattern, false otherwise.
/// See http://msdn.microsoft.com/en-us/library/swf8kaxw(v=VS.100).aspx
public static bool IsLike(this string s, string wildcardPattern) {
if (s == null || String.IsNullOrEmpty(wildcardPattern)) return false;
// turn into regex pattern, and match the whole string with ^$
var regexPattern = "^" + Regex.Escape(wildcardPattern) + "$";
// add support for ?, #, *, [], and [!]
regexPattern = regexPattern.Replace(@"\[!", "[^")
.Replace(@"\[", "[")
.Replace(@"\]", "]")
.Replace(@"\?", ".")
.Replace(@"\*", ".*")
.Replace(@"\#", @"\d");
var result = false;
try {
result = Regex.IsMatch(s, regexPattern);
}
catch (ArgumentException ex) {
throw new ArgumentException(String.Format("Invalid pattern: {0}", wildcardPattern), ex);
}
return result;
}
}
32> 小智..：
在此处查找更多示例:www.extensionmethod.net
33> johnc..：
类似于上面的字符串As和Is,但是对所有对象都是全局的.
这很简单,但是我用这些来减轻拳击的parens爆炸.
public static class ExtensionMethods_Object
{
[DebuggerStepThrough()]
public static bool Is(this object item) where T : class
{
return item is T;
}
[DebuggerStepThrough()]
public static bool IsNot(this object item) where T : class
{
return !(item.Is());
}
[DebuggerStepThrough()]
public static T As(this object item) where T : class
{
return item as T;
}
}
///
/// Converts any type in to an Int32
///
/// Any Object
/// Value to convert
/// The integer, 0 if unsuccessful
public static int ToInt32(this T value)
{
int result;
if (int.TryParse(value.ToString(), out result))
{
return result;
}
return 0;
}
///
/// Converts any type in to an Int32 but if null then returns the default
///
/// Value to convert
/// Any Object
/// Default to use
/// The defaultValue if unsuccessful
public static int ToInt32(this T value, int defaultValue)
{
int result;
if (int.TryParse(value.ToString(), out result))
{
return result;
}
return defaultValue;
}
例:
int number = "123".ToInt32();
要么:
int badNumber = "a".ToInt32(100); // Returns 100 since a is nan
public static FileInfo SetExtension(this FileInfo fileInfo, string extension)
{
return new FileInfo(Path.ChangeExtension(fileInfo.FullName, extension));
}
public static FileInfo SetDirectory(this FileInfo fileInfo, string directory)
{
return new FileInfo(Path.Combine(directory, fileInfo.Name));
}
是的,你可以把它放在codeplex中
38> 小智..：
一些我最好的方法扩展(我有很多!):
public static T ToEnum(this string str) where T : struct
{
return (T)Enum.Parse(typeof(T), str);
}
//DayOfWeek sunday = "Sunday".ToEnum();
public static string ToString(this IEnumerable collection, string separator)
{
return ToString(collection, t => t.ToString(), separator);
}
public static string ToString(this IEnumerable collection, Func stringElement, string separator)
{
StringBuilder sb = new StringBuilder();
foreach (var item in collection)
{
sb.Append(stringElement(item));
sb.Append(separator);
}
return sb.ToString(0, Math.Max(0, sb.Length - separator.Length)); // quita el ultimo separador
}
//new []{1,2,3}.ToString(i=>i*2, ", ") --> "2, 4, 6"
此外,接下来的几乎意味着能够在几乎任何情况下继续在同一行,而不是声明新的变量,然后删除状态:
public static R Map(this T t, Func func)
{
return func(t);
}
ExpensiveFindWally().Map(wally=>wally.FirstName + " " + wally.LastName)
public static R TryCC(this T t, Func func)
where T : class
where R : class
{
if (t == null) return null;
return func(t);
}
public static R? TryCS(this T t, Func func)
where T : class
where R : struct
{
if (t == null) return null;
return func(t);
}
public static R? TryCS(this T t, Func func)
where T : class
where R : struct
{
if (t == null) return null;
return func(t);
}
public static R TrySC(this T? t, Func func)
where T : struct
where R : class
{
if (t == null) return null;
return func(t.Value);
}
public static R? TrySS(this T? t, Func func)
where T : struct
where R : struct
{
if (t == null) return null;
return func(t.Value);
}
public static R? TrySS(this T? t, Func func)
where T : struct
where R : struct
{
if (t == null) return null;
return func(t.Value);
}
//int? bossNameLength = Departament.Boss.TryCC(b=>b.Name).TryCS(s=>s.Length);
public static T ThrowIfNullS(this T? t, string mensaje)
where T : struct
{
if (t == null)
throw new NullReferenceException(mensaje);
return t.Value;
}
public static T ThrowIfNullC(this T t, string mensaje)
where T : class
{
if (t == null)
throw new NullReferenceException(mensaje);
return t;
}
public static T Do(this T t, Action action)
{
action(t);
return t;
}
//Button b = new Button{Content = "Click"}.Do(b=>Canvas.SetColumn(b,2));
public static T TryDo(this T t, Action action) where T : class
{
if (t != null)
action(t);
return t;
}
public static T? TryDoS(this T? t, Action action) where T : struct
{
if (t != null)
action(t.Value);
return t;
}
希望它看起来不像来自火星:)
39> Rinat Abdull..：
与Timespan相关的扩展,例如:
public static TimeSpan Seconds(this int seconds)
{
return TimeSpan.FromSeconds(seconds);
}
public static TimeSpan Minutes(this int minutes)
{
return TimeSpan.FromMinutes(minutes);
}
允许使用:
1.Seconds()
20.Minutes()
锁定扩展名如:
public static IDisposable GetReadLock(this ReaderWriterLockSlim slimLock)
{
slimLock.EnterReadLock();
return new DisposableAction(slimLock.ExitReadLock);
}
public static IDisposable GetWriteLock(this ReaderWriterLockSlim slimLock)
{
slimLock.EnterWriteLock();
return new DisposableAction(slimLock.ExitWriteLock);
}
public static IDisposable GetUpgradeableReadLock(this ReaderWriterLockSlim slimLock)
{
slimLock.EnterUpgradeableReadLock();
return new DisposableAction(slimLock.ExitUpgradeableReadLock);
}
允许使用锁定:
using (lock.GetUpgradeableReadLock())
{
// try read
using (lock.GetWriteLock())
{
//do write
}
}
public static class EnumerableExtensions
{
[Pure]
public static U MapReduce(this IEnumerable enumerable, Func map, Func reduce)
{
CodeContract.RequiresAlways(enumerable != null);
CodeContract.RequiresAlways(enumerable.Skip(1).Any());
CodeContract.RequiresAlways(map != null);
CodeContract.RequiresAlways(reduce != null);
return enumerable.AsParallel().Select(map).Aggregate(reduce);
}
[Pure]
public static U MapReduce(this IList list, Func map, Func reduce)
{
CodeContract.RequiresAlways(list != null);
CodeContract.RequiresAlways(list.Count >= 2);
CodeContract.RequiresAlways(map != null);
CodeContract.RequiresAlways(reduce != null);
U result = map(list[0]);
for (int i = 1; i < list.Count; i++)
{
result = reduce(result,map(list[i]));
}
return result;
}
//Parallel version; creates garbage
[Pure]
public static U MapReduce(this IList list, Func map, Func reduce)
{
CodeContract.RequiresAlways(list != null);
CodeContract.RequiresAlways(list.Skip(1).Any());
CodeContract.RequiresAlways(map != null);
CodeContract.RequiresAlways(reduce != null);
U[] mapped = new U[list.Count];
Parallel.For(0, mapped.Length, i =>
{
mapped[i] = map(list[i]);
});
U result = mapped[0];
for (int i = 1; i < list.Count; i++)
{
result = reduce(result, mapped[i]);
}
return result;
}
}
通过在合同检查中调用"Count"来枚举"可枚举"是不是有点危险？或者这不是运行时检查？
43> Kenny Eliass..：
有时,使用自定义分隔符在列表中的选定元素上写出字符串非常方便.
例如,如果你有一个List并想要用逗号分隔出姓氏,你可以这样做.
string result = string.Empty;
foreach (var person in personList) {
result += person.LastName + ", ";
}
result = result.Substring(0, result.Length - 2);
return result;
public static T BinarySearch(this IList list, Func keySelector, TKey key)
where TKey : IComparable
{
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");
}
using System;
using System.Windows.Forms;
///
/// Extension methods acting on Control objects.
///
internal static class ControlExtensionMethods
{
///
/// Invokes the given action on the given control's UI thread, if invocation is needed.
///
/// Control on whose UI thread to possibly invoke.
/// Action to be invoked on the given control.
public static void MaybeInvoke(this Control control, Action action)
{
if (control != null && control.InvokeRequired)
{
control.Invoke(action);
}
else
{
action();
}
}
///
/// Maybe Invoke a Func that returns a value.
///
/// Return type of func.
/// Control on which to maybe invoke.
/// Function returning a value, to invoke.
/// The result of the call to func.
public static T MaybeInvoke(this Control control, Func func)
{
if (control != null && control.InvokeRequired)
{
return (T)(control.Invoke(func));
}
else
{
return func();
}
}
}
用法:
myForm.MaybeInvoke(() => this.Text = "Hello world");
// Sometimes the control might be null, but that's okay.
var dialogResult = this.Parent.MaybeInvoke(() => MessageBox.Show(this, "Yes or no?", "Choice", MessageBoxButtons.YesNo));
DirectoryInfo dir = new DirectoryInfo(@"C:\test\myShareDir");
Console.WriteLine(dir.IsSameFileAs(@"\\myMachineName\myShareDir"));
FileInfo file = new FileInfo(@"C:\test\myShareDir\file.txt");
Console.WriteLine(file.IsSameFileAs(@"\\myMachineName\myShareDir\file.txt"));
码:
public static class FileExtensions
{
struct BY_HANDLE_FILE_INFORMATION
{
public uint FileAttributes;
public System.Runtime.InteropServices.ComTypes.FILETIME CreationTime;
public System.Runtime.InteropServices.ComTypes.FILETIME LastAccessTime;
public System.Runtime.InteropServices.ComTypes.FILETIME LastWriteTime;
public uint VolumeSerialNumber;
public uint FileSizeHigh;
public uint FileSizeLow;
public uint NumberOfLinks;
public uint FileIndexHigh;
public uint FileIndexLow;
}
//
// CreateFile constants
//
const uint FILE_SHARE_READ = 0x00000001;
const uint OPEN_EXISTING = 3;
const uint GENERIC_READ = (0x80000000);
const uint FILE_FLAG_BACKUP_SEMANTICS = 0x02000000;
[DllImport("kernel32.dll", SetLastError = true)]
static extern IntPtr CreateFile(
string lpFileName,
uint dwDesiredAccess,
uint dwShareMode,
IntPtr lpSecurityAttributes,
uint dwCreationDisposition,
uint dwFlagsAndAttributes,
IntPtr hTemplateFile);
[DllImport("kernel32.dll", SetLastError = true)]
static extern bool GetFileInformationByHandle(IntPtr hFile, out BY_HANDLE_FILE_INFORMATION lpFileInformation);
public static bool IsSameFileAs(this FileSystemInfo file, string path)
{
BY_HANDLE_FILE_INFORMATION fileInfo1, fileInfo2;
IntPtr ptr1 = CreateFile(file.FullName, GENERIC_READ, FILE_SHARE_READ, IntPtr.Zero, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, IntPtr.Zero);
if ((int)ptr1 == -1)
{
System.ComponentModel.Win32Exception e = new System.ComponentModel.Win32Exception(Marshal.GetLastWin32Error());
throw e;
}
IntPtr ptr2 = CreateFile(path, GENERIC_READ, FILE_SHARE_READ, IntPtr.Zero, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, IntPtr.Zero);
if ((int)ptr2 == -1)
{
System.ComponentModel.Win32Exception e = new System.ComponentModel.Win32Exception(Marshal.GetLastWin32Error());
throw e;
}
GetFileInformationByHandle(ptr1, out fileInfo1);
GetFileInformationByHandle(ptr2, out fileInfo2);
return ((fileInfo1.FileIndexHigh == fileInfo2.FileIndexHigh) &&
(fileInfo1.FileIndexLow == fileInfo2.FileIndexLow));
}
}
你不应该关闭那些文件句柄吗？ 这不是使用扩展方法.它只是一个静态类.
48> Zack Elan..：
词典的Pythonic方法:
///
/// If a key exists in a dictionary, return its value,
/// otherwise return the default value for that type.
///
public static U GetWithDefault(this Dictionary dict, T key)
{
return dict.GetWithDefault(key, default(U));
}
///
/// If a key exists in a dictionary, return its value,
/// otherwise return the provided default value.
///
public static U GetWithDefault(this Dictionary dict, T key, U defaultValue)
{
return dict.ContainsKey(key)
? dict[key]
: defaultValue;
}
当您想要将时间戳附加到文件名以确保唯一性时很有用.
///
/// Format a DateTime as a string that contains no characters
//// that are banned from filenames, such as ':'.
///
/// YYYY-MM-DD_HH.MM.SS
public static string ToFilenameString(this DateTime dt)
{
return dt.ToString("s").Replace(":", ".").Replace('T', '_');
}
更好地使用TryGetValue,您正在进行两次查找而不是一次查找.
49> 小智..：
我通常使用这种扩展方法使用匿名类型来获取字典ala ruby
public static Dictionary ToDictionary(this object o)
{
var dictionary = new Dictionary();
foreach (var propertyInfo in o.GetType().GetProperties())
{
if (propertyInfo.GetIndexParameters().Length == 0)
{
dictionary.Add(propertyInfo.Name, propertyInfo.GetValue(o, null));
}
}
return dictionary;
}
你可以使用它
var dummy = new { color = "#000000", width = "100%", id = "myid" };
Dictionary dict = dummy.ToDictionary();
并采用扩展方法
public static void ForEach(this IEnumerable source, Action action)
{
foreach (T item in source)
{
action(item);
}
}
///
/// Gets the key using from .
///
/// The dictionary value.
/// The dictionary.
/// The case insensitive key.
///
/// An existing key; or if not found.
///
public static string GetKeyIgnoringCase(this IDictionary dictionary, string caseInsensitiveKey)
{
if (string.IsNullOrEmpty(caseInsensitiveKey)) return string.Empty;
foreach (string key in dictionary.Keys)
{
if (key.Equals(caseInsensitiveKey, StringComparison.InvariantCultureIgnoreCase))
{
return key;
}
}
return string.Empty;
}
public interface MXmlSerializable { }
public static class XmlSerializable {
public static string ToXml(this MXmlSerializable self) {
if (self == null) throw new ArgumentNullException();
var serializer = new XmlSerializer(self.GetType());
using (var writer = new StringWriter()) {
serializer.Serialize(writer, self);
return writer.GetStringBuilder().ToString();
}
}
public static T FromXml(string xml) where T : MXmlSerializable {
var serializer = new XmlSerializer(typeof(T));
return (T)serializer.Deserialize(new StringReader(xml));
}
}
然后一个类将它混合在一起:
public class Customer : MXmlSerializable {
public string Name { get; set; }
public bool Preferred { get; set; }
}
用法很简单:
var customer = new Customer {
Name = "Guybrush Threepwood",
Preferred = true };
var xml = customer.ToXml();
public static T ObjectWithMin(this IEnumerable sequence, Func predicate)
where T : class
where TResult : IComparable
{
if (!sequence.Any()) return null;
//get the first object with its predicate value
var seed = sequence.Select(x => new {Object = x, Value = predicate(x)}).FirstOrDefault();
//compare against all others, replacing the accumulator with the lesser value
//tie goes to first object found
return
sequence.Select(x => new {Object = x, Value = predicate(x)})
.Aggregate(seed,(acc, x) => acc.Value.CompareTo(x.Value) <= 0 ? acc : x).Object;
}
public static T ObjectWithMax(this IEnumerable sequence, Func predicate)
where T : class
where TResult : IComparable
{
if (!sequence.Any()) return null;
//get the first object with its predicate value
var seed = sequence.Select(x => new {Object = x, Value = predicate(x)}).FirstOrDefault();
//compare against all others, replacing the accumulator with the greater value
//tie goes to last object found
return
sequence.Select(x => new {Object = x, Value = predicate(x)})
.Aggregate(seed, (acc, x) => acc.Value.CompareTo(x.Value) > 0 ? acc : x).Object;
}
用法:
var myObject = myList.ObjectWithMin(x=>x.PropA);
这些方法基本上取代了像
var myObject = myList.OrderBy(x=>x.PropA).FirstOrDefault(); //O(nlog(n)) and unstable
和
var myObject = myList.Where(x=>x.PropA == myList.Min(x=>x.PropA)).FirstOrDefault(); //O(N^2) but stable
和
var minValue = myList.Min(x=>x.PropA);
var myObject = myList.Where(x=>x.PropA == minValue).FirstOrDefault(); //not a one-liner, and though linear and stable it's slower (evaluates the enumerable twice)
57> HuseyinUslu..：
这是一个位图扩展,可以将位图转换为灰度;
public static Bitmap GrayScale(this Bitmap bitmap)
{
Bitmap newBitmap = new Bitmap(bitmap.Width, bitmap.Height);
Graphics g = Graphics.FromImage(newBitmap);
//the grayscale ColorMatrix
ColorMatrix colorMatrix = new ColorMatrix(new float[][] {
new float[] {.3f, .3f, .3f, 0, 0},
new float[] {.59f, .59f, .59f, 0, 0},
new float[] {.11f, .11f, .11f, 0, 0},
new float[] {0, 0, 0, 1, 0},
new float[] {0, 0, 0, 0, 1}
});
ImageAttributes attributes = new ImageAttributes();
attributes.SetColorMatrix(colorMatrix);
g.DrawImage(bitmap, new Rectangle(0, 0, bitmap.Width, bitmap.Height), 0, 0, bitmap.Width, bitmap.Height, GraphicsUnit.Pixel, attributes);
g.Dispose();
return newBitmap;
}
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