Copy value of node using reference into other node - xslt

Question

I'm trying to copy the value of an XML node referenced by an identifier into another node of the graph.
The orignal file looks like this:
<Root>
<Object id="Id1">
<FileName>file.png</FileName>
</Object>
<Description>
<Content>
<Title>Nice Object</Title>
<ObjectReference>Id1</ObjectReference>
</Content>
</Description></Root>
In XSLT, I use a variable to identify the value of the reference node identifier.
<xsl:template match="Content">
<xsl:variable name="IdObject">
<xsl:value-of select="ObjectReference"/>
</xsl:variable>
<Out>
<Title>
<xsl:value-of select="Title"/>
</Title>
<FileName>
<xsl:value-of select="//Object[#id='$IdObject']/Filename"/>
</FileName>
</Out></xsl:template>
The value of 'FileName' is not copied. I select the wrong reference node, I think. I tried with 'Ancestor::' and 'Parent::'. That doesn't work either.
Do you have an idea?
Thanks
I would like to obtain the following result :
<Out>
<Name>Nice Object</Name>
<FileName>file.png</FileName>
</Out>

Answer 1

XSLT has a built-in key mechanism for resolving cross-references. The following stylesheet:
XSLT 1.0
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
<xsl:key name="obj" match="Object" use="#id" />
<xsl:template match="Content">
<Out>
<xsl:copy-of select="Title"/>
<xsl:copy-of select="key('obj', ObjectReference)/FileName"/>
</Out>
</xsl:template>
<xsl:template match="text()"/>
</xsl:stylesheet>
applied to your input example, will return:
Result
<?xml version="1.0" encoding="UTF-8"?>
<Out>
<Title>Nice Object</Title>
<FileName>file.png</FileName>
</Out>
P.S. Your attempt did not work because:
You quoted the reference to the variable;
You used Filename instead of FileName.