msxml:脚本c# xml片段与XslCompiledTransform

你好，我有以下样式表

<xsl:template match="/">
<xsl:variable name="objGen">
  <xsl:value-of select="cuser:selListNodes('C:'Sitiosweb'Test'xsl'solimporta14.xml')" />
</xsl:variable> 
<xsl:if test="cuser:getNodesLength($objGen)!='0'">
  <xsl:for-each select="$objGen">
    <xsl:sort data-type="number" order="descending" select="substring(EL01,4,4)" /><xsl:value-of select="user:IncCount()" />
    <xsl:value-of disable-output-escaping="yes" select="EL01" />
    <xsl:value-of disable-output-escaping="yes" select="EL02" />
    <xsl:value-of disable-output-escaping="yes" select="EL03" />
    <xsl:value-of disable-output-escaping="yes" select="EL04" />
    <xsl:value-of disable-output-escaping="yes" select="EL05" />
  </xsl:for-each>
</xsl:if>

用c# 编写下面的脚本

<msxml:script language="C#" implements-prefix="cuser">
<msxml:using namespace="System.IO" />
public bool CheckFileExist(string strPath){
  return File.Exists(strPath);
}
public int getNodesLength(XPathNodeIterator objNodes){
   if(objNodes.Count > 0){ return(objNodes.Count); }else{ return(0); }
}
public XPathNodeIterator selListNodes(string nsetCtxt){
    XPathNavigator nav;
    XPathNodeIterator iterator;
    XPathDocument objGenXml = new XPathDocument(nsetCtxt);
    nav = objGenXml.CreateNavigator();
    XPathExpression xPathExpression = nav.Compile("//Listing/Elem");
    iterator = nav.Select(xPathExpression);
    return( iterator );
}

XML值为:

<Listing><Elem><EL01><![CDATA[SI-0001-14]]></EL01><EL04><![CDATA[35]]></EL04><EL02><![CDATA[351]]></EL02><EL03><![CDATA[1]]></EL03><EL04><![CDATA[35]]></EL04><EL05><![CDATA[21586]]></EL05><EL06><![CDATA[DALB, INC.]]></EL06><EL07><![CDATA[20140102]]></EL07><EL08><![CDATA[085225]]></EL08><EL09><![CDATA[]]></EL09><EL10><![CDATA[]]></EL10><EL11><![CDATA[]]></EL11><EL12><![CDATA[]]></EL12><EL13><![CDATA[]]></EL13><EL14><![CDATA[]]></EL14><EL15><![CDATA[]]></EL15></Elem><Elem><EL01><![CDATA[SI-0002-14]]></EL01><EL04><![CDATA[35]]></EL04><EL02><![CDATA[1228]]></EL02><EL03><![CDATA[1]]></EL03><EL04><![CDATA[35]]></EL04><EL05><![CDATA[22657]]></EL05><EL06><![CDATA[THE COCA COLA COMPANY]]></EL06><EL07><![CDATA[20140103]]></EL07><EL08><![CDATA[160102]]></EL08><EL09><![CDATA[]]></EL09><EL10><![CDATA[]]></EL10><EL11><![CDATA[]]></EL11><EL12><![CDATA[]]></EL12><EL13><![CDATA[]]></EL13><EL14><![CDATA[]]></EL14><EL15><![CDATA[]]></EL15></Elem></Listing>

但是当执行转换时，返回错误:

To use a result tree fragment in a path expression, first convert it to a set of nodes using msxsl: node-set ().

我的问题是有任何限制XML树与XslCompiledTransform类?或者我有一个错误，当使用XPathNodeIterator?