public override IXsltContextVariable ResolveVariable(string prefix, string name) {
string namespaceURI = this.LookupNamespace(prefix);
XmlQualifiedName qname = new XmlQualifiedName(name, namespaceURI);
IXsltContextVariable variable = this.manager.VariableScope.ResolveVariable(qname);
if (variable == null) {
throw XsltException.Create(Res.Xslt_InvalidVariable, qname.ToString());
}
return variable;
}