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…

有几次我发现自己想要Groovy的“安全导航”之类的东西。

从http://groovy.codehaus.org/Statements:

如果你在行走一个复杂的物体 图和不想要的 你可以抛出nullpointerexception 使用?。操作员而不是。来 执行导航。 Def foo = null Def bar = .myMethod()断言条 = =零

那么，您认为为它添加扩展方法是一个好主意吗? 喜欢的东西:

obj.SafelyNavigate(x => x.SomeProperty.MaybeAMethod().AnotherProperty);

我认为即使它也会带来一些麻烦，这也很好。

如果你认为这是个好主意:

您认为值类型应该发生什么?， 返回默认吗?扔吗?，通过泛型约束禁用它? 吞咽NullReferenceException来实现它会太冒险吗?， 你有什么建议?， 遍历表达式树执行每个调用或成员访问似乎很困难，而且有点过度(如果可能的话)，不是吗?

也许这只是一个坏主意:D，但我认为如果做得对，它是有用的。 如果没有类似的东西，你认为它有一些价值，我可能会给它一个机会，然后编辑答案。

我发现自己一遍又一遍地这样做……

public static bool EqualsIgnoreCase(this string a, string b)
{
    return string.Equals(a, b, StringComparison.OrdinalIgnoreCase);
}

.．.然后是StartsWithIgnoreCase, EndsWithIgnoreCase和ContainsIgnoreCase。

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。

public static bool In<T>(this T source, params T[] list)
{
  if(null==source) throw new ArgumentNullException("source");
  return list.Contains(source);
}

允许我替换:

if(reallyLongIntegerVariableName == 1 || 
    reallyLongIntegerVariableName == 6 || 
    reallyLongIntegerVariableName == 9 || 
    reallyLongIntegerVariableName == 11)
{
  // do something....
}

and

if(reallyLongStringVariableName == "string1" || 
    reallyLongStringVariableName == "string2" || 
    reallyLongStringVariableName == "string3")
{
  // do something....
}

and

if(reallyLongMethodParameterName == SomeEnum.Value1 || 
    reallyLongMethodParameterName == SomeEnum.Value2 || 
    reallyLongMethodParameterName == SomeEnum.Value3 || 
    reallyLongMethodParameterName == SomeEnum.Value4)
{
  // do something....
}

:

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....
}

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。