HL7 v2.x & FHIR Healthcare Auto-ID Protocols

public class Hl7RfidMessageBuilder
{
    public static string CreateColdStorageObservation(string tagId, string drugName, float tempCelsius, string lotNumber)
    {
        string timestamp = DateTime.UtcNow.ToString("yyyyMMddHHmmss");
        string messageControlId = Guid.NewGuid().ToString("N")[..10];

        // MLLP Encapsulated HL7 v2.5 Message
        var hl7 = new StringBuilder();
        hl7.Append(""); // <VT> Start Block

        // MSH - Message Header
        hl7.Append($"MSH|^~\&|RFID_EDGE_GATEWAY|PHARMACY_HUB|EPIC_HIS|CENTRAL_HOSPITAL|{timestamp}||ORU^R01|{messageControlId}|P|2.5\r");
        // PID - Patient/Entity Context
        hl7.Append($"PID|1||ASSET_PHARM_01^^^HOSPITAL||DRUG_INVENTORY||||||||||||||\r");
        // OBR - Observation Request
        hl7.Append($"OBR|1||RFID_SCAN_001|RFID_REFRIGERATOR_INVENTORY|||{timestamp}||||||||||||||||||\r");
        // OBX - Observation Data (Tag EPC, Drug Name, Temp, Lot)
        hl7.Append($"OBX|1|ST|TAG_EPC^RFID Tag Identifier||{tagId}||||||F\r");
        hl7.Append($"OBX|2|ST|DRUG_NAME^Item Description||{drugName}||||||F\r");
        hl7.Append($"OBX|3|NM|TEMP_C^Refrigeration Temp||{tempCelsius:F1}|degC|2.0-8.0|N|||F\r");
        hl7.Append($"OBX|4|ST|LOT_NUMBER^Batch Lot||{lotNumber}||||||F\r");

        hl7.Append("
"); // <FS><CR> End Block
        return hl7.ToString();
    }
}