How to send an array of byte via SOAPUI

So i enabled Inline Files to True and changed my SOAPUI projetct like this : 

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:wf="http://wf.soap.bdocinteractive.bdoc.com" xmlns:x-="http://xml.apache.org/xml-soap">
<soapenv:Header/>
<soapenv:Body>
<wf:executeWorkflowAction>
<wf:username>franck</wf:username>
<wf:password>franck</wf:password>
<wf:buiId>384</wf:buiId>
<wf:actionId>9600</wf:actionId>
<wf:comment>Ajout automatique pièce jointe par SOAP</wf:comment>
<wf:params>
<!--Zero or more repetitions:-->
<x-:item>
<x-:key>fileContentType</x-:key>
<x-:value>application/pdf</x-:value>
</x-:item>
<x-:item>
<x-:key>fileFileName</x-:key>
<x-:value>Constat.pdf</x-:value>
</x-:item>
<x-:item>
<x-:key>content</x-:key>
<x-:value>file:C:/Constat.pdf</x-:value>
</x-:item>

</wf:params>
</wf:executeWorkflowAction>
</soapenv:Body>
</soapenv:Envelope>

And it doesn't work with same error : 

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>
<soapenv:Fault>
<faultcode>soapenv:Server.userException</faultcode>
<faultstring>java.lang.ClassCastException: java.lang.String cannot be cast to [B</faultstring>
<detail>
<ns1:hostname xmlns:ns1="http://xml.apache.org/axis/">DESKTOP-C7BTNIN</ns1:hostname>
</detail>
</soapenv:Fault>
</soapenv:Body>
</soapenv:Envelope>