StringCollection scFuncIds = new StringCollection();
foreach (Function oFunction in arrFunctions)
{
    //get object id
    string objectId = oFunction.Properties.PROPUSER_DBOBJECTID;
    //get index of first separator
    int idxOfSlash = objectId.IndexOf("/", 1, objectId.Length - 1, StringComparison.InvariantCultureIgnoreCase);
    //cut off value before first separator together with this separator
    string objectIdWithoutProjectId = objectId.Substring(idxOfSlash + 1, (objectId.Length - idxOfSlash - 1));
    //add value to array
    scFuncIds.Add(objectIdWithoutProjectId);
}
//remove selection from all object and then select objects passed as in a list
new Edit().SelectObjects(m_TestProject.ProjectLinkFilePath, scFuncIds, true);