IMetadata metadata = (IMetadata)fc;
IPropertySet pset = metadata.Metadata;
IXmlPropertySet psetX = (IXmlPropertySet)metadata.Metadata;
string sValue = "myemail@company.com";
psetX.SetPropertyX("idinfo/ptcontac/cntinfo/cntemail", sValue,
sriXmlPropertyType.esriXPTText,
esriXmlSetPropertyAction.esriXSPAAddDuplicate, false);
metadata.Metadata = (IPropertySet)psetX;int counter = 0;
for (int counter=0; counter++; counter<10)
{
xmlPropSet.SetPropertyX(""idinfo/timeperd/timeinfo/mdattim/sngdate", "", esriXmlPropertyType.esriXPTText, esriXmlSetPropertyAction.esriXSPAAddDuplicate, false);
xmlPropSet.SetAttribute(String.Format(""idinfo/timeperd/timeinfo/mdattim/sngdate[{0}]/caldate", counter), "value", "<some date value>", esriXmlSetPropertyAction.esriXSPAAddOrReplace);
}