关于c＃：如何将字符串转换为大约300个字符，然后在单词分隔后显示[…]继续。


How convert string approximately 300 characters and then showing continuation with […] after a word break.?

我正在研究RSS提要。在rssfeed 中(string)标记建议使用大约300个字符，然后在断字后用[…]继续显示。

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<description>Lorem Ipsum is simply dummy text of the printing and typesetting
industry.
Lorem Ipsum has been the industry's standard dummy text ever since the 1500s,
when an unknown printer took a galley of type and scrambled it to make a type
specimen book. It has survived not only five centuries, but also the leap
into electronic typesetting, remaining essentially [...]</description>

代码：

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 TextWriter.WriteStartElement("item");
 TextWriter.WriteElementString("title", oFeedItem["CommPostSubject"].ToString());
 TextWriter.WriteElementString("description", oFeedItem["CommPostDescription"].
 ToString());
 TextWriter.WriteElementString("link", oFeedItem["CommPostSubjectUrl"].ToString());
 TextWriter.WriteEndElement();

如何处理字符串，方法是在换行符后显示带有[…]的继续符？

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您可以为string创建一个extension-method，如下所示：

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public static class MyExtensions{
        public static string SubText(this System.String str, System.Int32 charCount, System.String continues) {
            if (string.IsNullOrWhiteSpace(str) || str.Length < charCount)
                return str;
            str = str.Substring(0, charCount);
            int i = str.LastIndexOf("");
            if (i >= 0)
                str = str.Remove(i);
            str = String.Concat(str, continues);
            return str;
        }
}

并在代码中调用此扩展名：

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TextWriter
    .WriteElementString("description", oFeedItem["CommPostDescription"]
    .SubText(300," [...]"));
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 public static string TextAbstract(string text, int length)
        {
            if (text == null)
            {
                return string.Empty;
            }
            if (text.Length <= length)
            {
                return text;
            }
            text = text.Substring(0, length);
            text = text.Substring(0, text.LastIndexOf(""));
            return text +"...";
        }

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public static string Cutstring(string s, int min, int max)
{
    string res ="";
    int runto = s.Length;
    if (s.Length > max) runto = max;
    for (int i = 0; i < runto; i++)
    {
        if (i > min)
        {
            if ((s[i] == ' ') || (s[i] == '_')|| (s[i] == '-'))
            {
                break;
            }
        }
        res += s[i];
    }
    if (s.Length > max) res +="...";
    return res;
}

通过使用采用startindex的lastindexof的重载，可以少创建一个中间字符串。

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if (inputString.Length > maxlen)
{
    int breakindex = inputString.LastIndexOf("", maxlen);
    if (breakindex < 0)
    {
        breakindex = maxlen;
    }
    inputString = s.Substring(0, breakindex) +"...";
}

使用

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string ShorterString ="";
if ( YourLongString.Length > 300 )
{
     ShorterString = YourLongString.SubString ( 0, 300);
     ShorterString = ShorterString.SubString ( 0, ShorterString.LastIndexOf ("" ) + 1) +"...";

}
else { ShorterString = YourLongString; }
相关讨论

简单的解决方案：

  • 取前300个字符
  • 查找最后一个空格(或其他分词)
  • 附加省略号

代码：

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var fullText ="Lorem Ipsum....";
var first300 = fullText.SubString(0, 300);
var lastSpace = first300.LastIndexOf("");

var summary = string.format("{0}[...]", first300.SubString(0, lastSpace));
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