一些方便的字符串助手:

用法:

我讨厌不需要的空格尾随或引导字符串，因为字符串可以采取空值，这可能是棘手的，所以我使用这个:

public bool IsGroup { get { return !this.GroupName.IsNullOrTrimEmpty(); } }

这是另一个扩展方法，我使用一个新的验证框架，我正在试验。你可以看到regex扩展，帮助清理凌乱的regex:

public static bool IsRequiredWithLengthLessThanOrEqualNoSpecial(this String str, int length)
{
    return !str.IsNullOrTrimEmpty() &&
        str.RegexMatch(
            @"^[- \r\n\\\.!:*,@$%&""?\(\)\w']{1,{0}}$".RegexReplace(@"\{0\}", length.ToString()),
            RegexOptions.Multiline) == str;
}

来源:

public static class StringHelpers
{
    /// <summary>
    /// Same as String.IsNullOrEmpty except that
    /// it captures the Empty state for whitespace
    /// strings by Trimming first.
    /// </summary>
    public static bool IsNullOrTrimEmpty(this String helper)
    {
        if (helper == null)
            return true;
        else
            return String.Empty == helper.Trim();
    }

    public static int TrimLength(this String helper)
    {
        return helper.Trim().Length;
    }

    /// <summary>
    /// Returns the matched string from the regex pattern. The
    /// groupName is for named group match values in the form (?<name>group).
    /// </summary>
    public static string RegexMatch(this String helper, string pattern, RegexOptions options, string groupName)
    {
        if (groupName.IsNullOrTrimEmpty())
            return Regex.Match(helper, pattern, options).Value;
        else
            return Regex.Match(helper, pattern, options).Groups[groupName].Value;
    }

    public static string RegexMatch(this String helper, string pattern)
    {
        return RegexMatch(helper, pattern, RegexOptions.None, null);
    }

    public static string RegexMatch(this String helper, string pattern, RegexOptions options)
    {
        return RegexMatch(helper, pattern, options, null);
    }

    public static string RegexMatch(this String helper, string pattern, string groupName)
    {
        return RegexMatch(helper, pattern, RegexOptions.None, groupName);
    }

    /// <summary>
    /// Returns true if there is a match from the regex pattern
    /// </summary>
    public static bool IsRegexMatch(this String helper, string pattern, RegexOptions options)
    {
        return helper.RegexMatch(pattern, options).Length > 0;
    }

    public static bool IsRegexMatch(this String helper, string pattern)
    {
        return helper.IsRegexMatch(pattern, RegexOptions.None);
    }

    /// <summary>
    /// Returns a string where matching patterns are replaced by the replacement string.
    /// </summary>
    /// <param name="pattern">The regex pattern for matching the items to be replaced</param>
    /// <param name="replacement">The string to replace matching items</param>
    /// <returns></returns>
    public static string RegexReplace(this String helper, string pattern, string replacement, RegexOptions options)
    {
        return Regex.Replace(helper, pattern, replacement, options);
    }

    public static string RegexReplace(this String helper, string pattern, string replacement)
    {
        return Regex.Replace(helper, pattern, replacement, RegexOptions.None);
    }
}

我喜欢做很多正则表达式，所以我认为这些比添加using语句和额外的代码来处理命名组更容易。

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。

下面是我用来减少提取单个属性的一些方法:

public static T GetAttribute<T>(this ICustomAttributeProvider provider, bool inherit = false, int index = 0) where T : Attribute
{
    return provider.GetAttribute(typeof(T), inherit, index) as T;
}

public static Attribute GetAttribute(this ICustomAttributeProvider provider, Type type, bool inherit = false, int index = 0)
{
    bool exists = provider.IsDefined(type, inherit);
    if (!exists)
    {
        return null;
    }

    object[] attributes = provider.GetCustomAttributes(type, inherit);
    if (attributes != null && attributes.Length != 0)
    {
        return attributes[index] as Attribute;
    }
    else
    {
        return null;
    }
}

用法(枚举描述hack的实现):

public static string GetDescription(this Enum value)
{
    var fieldInfo = value.GetType().GetField(value.ToString());
    var attribute = fieldInfo.GetAttribute<DescriptionAttribute>();
    return attribute != null ? attribute.Description : null;
}

请随意将其包含在CodePlex项目中!

有时需要有类的实例，不管是否有效，但不是null

public static T Safe<T>(this T obj) where T : new()
{
    if (obj == null)
    {
        obj = new T();
    }

    return obj;
}

用法如下:

MyClass myClass = Provider.GetSomeResult();
string temp = myClass.Safe().SomeValue;

而不是:

MyClass myClass = Provider.GetSomeResult();
string temp = "some default value";
if (myClass != null)
{
        temp = myClass.SomeValue;
}

如果是口是心非的话，我很抱歉，但我没有找到。

这是我今天刚创建的一个。

// requires .NET 4

public static TReturn NullOr<TIn, TReturn>(this TIn obj, Func<TIn, TReturn> 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<TIn, TReturn>(this TIn obj, Func<TIn, TReturn> func,
        TReturn elseValue) where TIn : class
    { return obj != null ? func(obj) : elseValue; }
public static TReturn NullOr<TIn, TReturn>(this TIn obj, Func<TIn, TReturn> func)
        where TIn : class
    { return obj != null ? func(obj) : default(TReturn); }

它让你这样做:

var lname = thingy.NullOr(t => t.Name).NullOr(n => n.ToLower());

哪个比这个更流畅，(依我看)更容易阅读:

var lname = (thingy != null ? thingy.Name : null) != null
    ? thingy.Name.ToLower() : null;

我创建了一个扩展方法来在下拉菜单中选择一个项目。

下面是代码

 public static class Utilities
{
    public enum DropDownListSelectionType
    {
        ByValue,
        ByText
    }

    public static void SelectItem(this  System.Web.UI.WebControls.DropDownList drp, string selectedValue, DropDownListSelectionType type)
    {
        drp.ClearSelection();
        System.Web.UI.WebControls.ListItem li;
        if (type == DropDownListSelectionType.ByValue)
            li = drp.Items.FindByValue(selectedValue.Trim());
        else
            li = drp.Items.FindByText(selectedValue.Trim());
        if (li != null)
            li.Selected = true;
    }}

此方法可以由以下代码行调用，以按文本进行选择

DropDownList1.SelectItem("ABCD", Utilities.DropDownListSelectionType.ByText);

或者按值选择

DropDownList1.SelectItem("11", Utilities.DropDownListSelectionType.ByValue);

上面的代码不选择任何东西，如果它不能找到传递进来的文本/值。