我使用以下内容XPATH Query列出站点下的对象。ListObject[@Title='SomeValue']。SomeValue是动态的。只要SomeValue没有撇号(’),此查询就起作用。也尝试使用转义序列。没用
XPATH Query
ListObject[@Title='SomeValue']
我究竟做错了什么?
令人惊讶地,这很难做到。
看一下XPath Recommendation,您将看到它定义了一个字面量为:
Literal ::= '"' [^"]* '"' | "'" [^']* "'"
也就是说,XPath表达式中的字符串文字可以包含撇号或双引号,但不能同时包含两者。
您不能使用转义来解决此问题。像这样的文字:
'Some'Value'
将匹配以下XML文本:
Some'Value
这确实意味着,可能有一部分XML文本无法生成匹配的XPath文字,例如:
<elm att=""&apos"/>
但这并不意味着不可能将文本与XPath匹配,这很棘手。在任何情况下,如果您要匹配的值都包含单引号和双引号,则可以构造一个表达式concat来生成将要匹配的文本:
concat
elm[@att=concat('"', "'")]
因此,这导致了这一点,这比我希望的要复杂得多:
/// <summary> /// Produce an XPath literal equal to the value if possible; if not, produce /// an XPath expression that will match the value. /// /// Note that this function will produce very long XPath expressions if a value /// contains a long run of double quotes. /// </summary> /// <param name="value">The value to match.</param> /// <returns>If the value contains only single or double quotes, an XPath /// literal equal to the value. If it contains both, an XPath expression, /// using concat(), that evaluates to the value.</returns> static string XPathLiteral(string value) { // if the value contains only single or double quotes, construct // an XPath literal if (!value.Contains("\"")) { return "\"" + value + "\""; } if (!value.Contains("'")) { return "'" + value + "'"; } // if the value contains both single and double quotes, construct an // expression that concatenates all non-double-quote substrings with // the quotes, e.g.: // // concat("foo", '"', "bar") StringBuilder sb = new StringBuilder(); sb.Append("concat("); string[] substrings = value.Split('\"'); for (int i = 0; i < substrings.Length; i++ ) { bool needComma = (i>0); if (substrings[i] != "") { if (i > 0) { sb.Append(", "); } sb.Append("\""); sb.Append(substrings[i]); sb.Append("\""); needComma = true; } if (i < substrings.Length - 1) { if (needComma) { sb.Append(", "); } sb.Append("'\"'"); } } sb.Append(")"); return sb.ToString(); }
是的,我在所有边缘情况下都进行了测试。这就是逻辑如此愚蠢的原因:
foreach (string s in new[] { "foo", // no quotes "\"foo", // double quotes only "'foo", // single quotes only "'foo\"bar", // both; double quotes in mid-string "'foo\"bar\"baz", // multiple double quotes in mid-string "'foo\"", // string ends with double quotes "'foo\"\"", // string ends with run of double quotes "\"'foo", // string begins with double quotes "\"\"'foo", // string begins with run of double quotes "'foo\"\"bar" // run of double quotes in mid-string }) { Console.Write(s); Console.Write(" = "); Console.WriteLine(XPathLiteral(s)); XmlElement elm = d.CreateElement("test"); d.DocumentElement.AppendChild(elm); elm.SetAttribute("value", s); string xpath = "/root/test[@value = " + XPathLiteral(s) + "]"; if (d.SelectSingleNode(xpath) == elm) { Console.WriteLine("OK"); } else { Console.WriteLine("Should have found a match for {0}, and didn't.", s); } } Console.ReadKey(); }