问题
今天在修改程序的一个BUG时，竟然发现selectSingleNode方法不支持contains Xpath函数,感到很奇怪。在网上和MSDN也没有发现官方言论表明selectSingleNode不支持contains 函数。
当时我的情景大概是这样的：
1、Xml文档的结构
<?
xml version="1.0"
?>
<
xsf:xDocumentClass
xmlns:xsf
="http://schemas.microsoft.com/office/infopath/2003/solutionDefinition"
>
<
xsf:errorCondition
expressionContext
="T_SUBTITLE/ICHANNELNUM"
>
<
xsf:subExpression
>
Xpath_getSigleNodeValue("T_SUBTITLE/ICHANNELNUM","../ITIMESUSAGE")
<
1
</xsf:subExpression
>
</
xsf:errorCondition
>
-
<
xsf:errorCondition
expressionContext
="T_DESCAUTHORIZE/ITIMESUSAGE"
>
<
xsf:subExpression
>
Xpath_getSigleNodeValue("T_DESCAUTHORIZE/ITIMESUSAGE","../ICHANNELNUM")
<
1
</xsf:subExpression
>
</
xsf:errorCondition
>
</
xsf:xDocumentClass
>
2.我的实现。
我希望通过代码找到expressionContext不等于T_SUBTITLE/ICHANNELNUM，并且xsf:suExpression中包含字符串"ICHANNELNUM"的节点。我书写了以下代码来实现：
//
aObjView_Xsf是存储上述Xml的文档对象
var
aObjView_Xsf
=
new
ActiveXObject('MSXML2.DOMDocument');
aObjView_Xsf.load(
"
test.xml
"
);
var
objerrorConditions
=
aObjView_Xsf.selectSingleNode(
"
xsf:xDocumentClass/xsf:customValidation/xsf:errorCondition[@expressionContext!='
"
+
strBinding
+
"
' and contains(xsf:subExpression,'
"
+
fieldName
+
"
')]
"
);
这时IE报出错误：contains是未实现的方法！。这下我就晕了，明明在Xpath的参考手册，MSDN上都写着contains是支持的方法。
原因
难道真的不支持？
查阅MSDN我发现还有以下Xpath函数：
| Microsoft XML Core Services (MSXML) 4.0 - XPath Reference |
|
String Functions
| concat | Returns the concatenation of the arguments. |
| contains | Returns true if the first argument string contains the second argument string; otherwise returns false. |
| normalize-space | Returns the argument string with the white space stripped. |
| starts-with | Returns true if the first argument string starts with the second argument string; otherwise returns false. |
| string | Converts an object to a string. |
| string-length | Returns the number of characters in the string. |
| substring | Returns the substring of the first argument starting at the position specified in the second argument and the length specified in the third argument. |
| substring-after | Returns the substring of the first argument string that follows the first occurrence of the second argument string in the first argument string. |
| substring-before | Returns the substring of the first argument string that precedes the first occurrence of the second argument string in the first argument string. |
| translate | Returns the first argument string with occurrences of characters in the second argument string replaced by the character at the corresponding position in the third argument string. |
难道就只有contains不支持吗？其他函数呢？为了证实我的想法，我尝试了上述所有函数，IE都报出同样的错误，原来都不支持！
原来只有4.0版本的支持
我发现这些Xpath函数的说明在MSXML 4.0 SDK下，难道只有4.0版本支持？于是我把代码进行了修改:
//
aObjView_Xsf是存储上述Xml的文档对象
var
aObjView_Xsf
=
new
ActiveXObject('Msxml2.DOMDocument.
4.0
');
aObjView_Xsf.load(
"
test.xml
"
);
var
objerrorConditions
=
aObjView_Xsf.selectSingleNode(
"
xsf:xDocumentClass/xsf:customValidation/xsf:errorCondition[@expressionContext!='
"
+
strBinding
+
"
' and contains(xsf:subExpression,'
"
+
fieldName
+
"
')]
"
);
运行程序，竟然不再抛出contains函数不支持的错误了，但是出现另外一个错误，xsf是未定义的前缀。对，应该是没有声明名称空间。我对代码再次进行了修改：
var
aObjView_Xsf
=
new
ActiveXObject('Msxml2.DOMDocument.
4.0
');
aObjView_Xsf.load(
"
test.xml
"
);
aObjView_Xsf.setProperty(
"
SelectionNamespaces
"
,
"
xmlns:xsf='http://schemas.microsoft.com/office/infopath/2003/solutionDefinition'
"
);
var
objerrorConditions
=
aObjView_Xsf.selectSingleNode(
"
xsf:xDocumentClass/xsf:customValidation/xsf:errorCondition[@expressionContext!='
"
+
strBinding
+
"
' and contains(xsf:subExpression,'
"
+
fieldName
+
"
')]
"
);
运行程序，测试通过！于是我下了这样一个结论：只有Msxml2.DOMDocument.4.0以上版本才支持这些Xpath函数。但是这个结论对吗？我自己也不敢确定。
不只Msxml2.DOMDocument 4.0以上版本支持contains等Xpath函数
我进一步的查找了一些资料，都没有信息表明Msxml2.DOMDocument 2.0不支持这些Xpath函数。到底Msxml2.DOMDocument 2.0、Msxml2.DOMDocument 3.0为什么支持类似等于、不等于、大于这样的操作符，而无法识别contains这样的函数呢？直到我发现了这个方法：setProperty("SelectionLanguage", "XPath")。这时我恍然大悟，原来4.0以下版本的Msxml2.DOMDocument默认用类似正则匹配的方法来进行节点选取的，而4.0及以上版本默认采用Xpath作为默认的选择语言。
我采用Msxml2.DOMDocument 2.0，将代码做以下修改也是可以正常运行的：
//
aObjView_Xsf是存储上述Xml的文档对象
var
aObjView_Xsf
=
new
ActiveXObject('MSXML2.DOMDocument');
aObjView_Xsf.setProperty(
"
SelectionLanguage
"
,
"
XPath
"
);
aObjView_Xsf.setProperty(
"
SelectionNamespaces
"
,
"
xmlns:xsf='http://schemas.microsoft.com/office/infopath/2003/solutionDefinition'
"
);
aObjView_Xsf.load(
"
test.xml
"
);
var
objerrorConditions
=
aObjView_Xsf.selectSingleNode(
"
xsf:xDocumentClass/xsf:customValidation/xsf:errorCondition[@expressionContext!='
"
+
strBinding
+
"
' and contains(xsf:subExpression,'
"
+
fieldName
+
"
')]
"
);
