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。
您可以从Random类中获得许多功能。
下面是我经常使用的一些扩展方法。有了这些，除了Next和NextDouble, Random类还提供了NextBool, NextChar, NextDateTime, NextTimeSpan, NextDouble(接受minValue和maxValue参数)，以及我个人最喜欢的NextString。还有更多(NextByte, NextShort, NextLong等);但这些主要是为了完整性，并不经常使用。所以我没有在这里包含它们(这段代码已经足够长了!)。
// todo: implement additional CharType values (e.g., AsciiAny)
public enum CharType {
AlphabeticLower,
AlphabeticUpper,
AlphabeticAny,
AlphanumericLower,
AlphanumericUpper,
AlphanumericAny,
Numeric
}
public static class RandomExtensions {
// 10 digits vs. 52 alphabetic characters (upper & lower);
// probability of being numeric: 10 / 62 = 0.1612903225806452
private const double AlphanumericProbabilityNumericAny = 10.0 / 62.0;
// 10 digits vs. 26 alphabetic characters (upper OR lower);
// probability of being numeric: 10 / 36 = 0.2777777777777778
private const double AlphanumericProbabilityNumericCased = 10.0 / 36.0;
public static bool NextBool(this Random random, double probability) {
return random.NextDouble() <= probability;
}
public static bool NextBool(this Random random) {
return random.NextDouble() <= 0.5;
}
public static char NextChar(this Random random, CharType mode) {
switch (mode) {
case CharType.AlphabeticAny:
return random.NextAlphabeticChar();
case CharType.AlphabeticLower:
return random.NextAlphabeticChar(false);
case CharType.AlphabeticUpper:
return random.NextAlphabeticChar(true);
case CharType.AlphanumericAny:
return random.NextAlphanumericChar();
case CharType.AlphanumericLower:
return random.NextAlphanumericChar(false);
case CharType.AlphanumericUpper:
return random.NextAlphanumericChar(true);
case CharType.Numeric:
return random.NextNumericChar();
default:
return random.NextAlphanumericChar();
}
}
public static char NextChar(this Random random) {
return random.NextChar(CharType.AlphanumericAny);
}
private static char NextAlphanumericChar(this Random random, bool uppercase) {
bool numeric = random.NextBool(AlphanumericProbabilityNumericCased);
if (numeric)
return random.NextNumericChar();
else
return random.NextAlphabeticChar(uppercase);
}
private static char NextAlphanumericChar(this Random random) {
bool numeric = random.NextBool(AlphanumericProbabilityNumericAny);
if (numeric)
return random.NextNumericChar();
else
return random.NextAlphabeticChar(random.NextBool());
}
private static char NextAlphabeticChar(this Random random, bool uppercase) {
if (uppercase)
return (char)random.Next(65, 91);
else
return (char)random.Next(97, 123);
}
private static char NextAlphabeticChar(this Random random) {
return random.NextAlphabeticChar(random.NextBool());
}
private static char NextNumericChar(this Random random) {
return (char)random.Next(48, 58);
}
public static DateTime NextDateTime(this Random random, DateTime minValue, DateTime maxValue) {
return DateTime.FromOADate(
random.NextDouble(minValue.ToOADate(), maxValue.ToOADate())
);
}
public static DateTime NextDateTime(this Random random) {
return random.NextDateTime(DateTime.MinValue, DateTime.MaxValue);
}
public static double NextDouble(this Random random, double minValue, double maxValue) {
if (maxValue < minValue)
throw new ArgumentException("Minimum value must be less than maximum value.");
double difference = maxValue - minValue;
if (!double.IsInfinity(difference))
return minValue + (random.NextDouble() * difference);
else {
// to avoid evaluating to Double.Infinity, we split the range into two halves:
double halfDifference = (maxValue * 0.5) - (minValue * 0.5);
// 50/50 chance of returning a value from the first or second half of the range
if (random.NextBool())
return minValue + (random.NextDouble() * halfDifference);
else
return (minValue + halfDifference) + (random.NextDouble() * halfDifference);
}
}
public static string NextString(this Random random, int numChars, CharType mode) {
char[] chars = new char[numChars];
for (int i = 0; i < numChars; ++i)
chars[i] = random.NextChar(mode);
return new string(chars);
}
public static string NextString(this Random random, int numChars) {
return random.NextString(numChars, CharType.AlphanumericAny);
}
public static TimeSpan NextTimeSpan(this Random random, TimeSpan minValue, TimeSpan maxValue) {
return TimeSpan.FromMilliseconds(
random.NextDouble(minValue.TotalMilliseconds, maxValue.TotalMilliseconds)
);
}
public static TimeSpan NextTimeSpan(this Random random) {
return random.NextTimeSpan(TimeSpan.MinValue, TimeSpan.MaxValue);
}
}
这是我写的唯一一个我经常使用的扩展。
它使得用System.Net.Mail发送电子邮件更容易一些。
public static class MailExtension
{
// GetEmailCreditial(out strServer) gets credentials from an XML file
public static void Send(this MailMessage email)
{
string strServer = String.Empty;
NetworkCredential credentials = GetEmailCreditial(out strServer);
SmtpClient client = new SmtpClient(strServer) { Credentials = credentials };
client.Send(email);
}
public static void Send(this IEnumerable<MailMessage> emails)
{
string strServer = String.Empty;
NetworkCredential credentials = GetEmailCreditial(out strServer);
SmtpClient client = new SmtpClient(strServer) { Credentials = credentials };
foreach (MailMessage email in emails)
client.Send(email);
}
}
// Example of use:
new MailMessage("info@myDomain.com","you@gmail.com","This is an important Subject", "Body goes here").Send();
//Assume email1,email2,email3 are MailMessage objects
new List<MailMessage>(){email1, email2, email}.Send();
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);
}
}
我的转换扩展，允许你做:
int i = myString.To<int>();
这是在TheSoftwareJedi.com上发布的
public static T To<T>(this IConvertible obj)
{
return (T)Convert.ChangeType(obj, typeof(T));
}
public static T ToOrDefault<T>
(this IConvertible obj)
{
try
{
return To<T>(obj);
}
catch
{
return default(T);
}
}
public static bool ToOrDefault<T>
(this IConvertible obj,
out T newObj)
{
try
{
newObj = To<T>(obj);
return true;
}
catch
{
newObj = default(T);
return false;
}
}
public static T ToOrOther<T>
(this IConvertible obj,
T other)
{
try
{
return To<T>obj);
}
catch
{
return other;
}
}
public static bool ToOrOther<T>
(this IConvertible obj,
out T newObj,
T other)
{
try
{
newObj = To<T>(obj);
return true;
}
catch
{
newObj = other;
return false;
}
}
public static T ToOrNull<T>
(this IConvertible obj)
where T : class
{
try
{
return To<T>(obj);
}
catch
{
return null;
}
}
public static bool ToOrNull<T>
(this IConvertible obj,
out T newObj)
where T : class
{
try
{
newObj = To<T>(obj);
return true;
}
catch
{
newObj = null;
return false;
}
}
您可以在失败时请求default(调用空白构造函数或“0”作为数字)，指定一个“default”值(我称之为“other”)，或请求null(其中T: class)。我还提供了两个静默异常模型和一个典型的TryParse模型，该模型返回一个bool值，指示所采取的操作，一个out参数保存新值。
我们的代码可以这样做
int i = myString.To<int>();
string a = myInt.ToOrDefault<string>();
//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<string>();
我不能让Nullable类型非常干净地滚入整个东西。我试了大约20分钟才认输。
