HL7-dotnetcore

This is a lightweight library for building and parsing HL7 2.x messages, for .Net Standard and .Net Core. It is not tied to any particular version of HL7 nor validates against one.

Object construction

Create a Message object and pass a raw HL7 message in text format

Message message = new Message(strMsg);

// Parse this message

bool isParsed = false;

try
{
    isParsed = message.ParseMessage();
}
catch(Exception ex)
{
    // Handle the exception
}

Adding a message header

For adding a header segment to a new message object, use the AddSegmentMSH() method, after constructing an empty message:

message.AddSegmentMSH(sendingApplication, sendingFacility, 
    receivingApplication, receivingFacility,
    security, messageType, 
    messageControlId, processingId, version);

⚠️ Notice that every HL7 message needs a header segment to be considered valid

Message extraction

If the HL7 message is coming from a MLLP connection (see the official documentation), the message needs to be cleared from the MLLP prefixes and suffixes. Also, consider there can be more than one message in a single MLLP frame.

For this purpose, there is an ExtractMessages() method, to be used as follows:

// extract the messages from a buffer containing a MLLP frame
var messages = MessageHelper.ExtractMessages(buffer);

// construct and process each message
foreach (var strMsg in messages)
{
    Message message = new Message(strMsg);
    message.ParseMessage(); // Required by most operations
    // do something with the message object
}

Bypass Validation

Message  message = new Message(strMsg)
message.ParseMessage(true);

Accessing Segments

Get list of all segments

List<Segment> segList = message.Segments();

Get List of list of repeated segments by name

For example if there are multiple IN1 segments

List<Segment> IN1List = message.Segments("IN1");

Access a particular occurrence from multiple IN1s providing the index

Note index 1 will return the 2nd element from list

Segment IN1_2 = message.Segments("IN1")[1];

Get count of IN1s

int countIN1 = message.Segments("IN1").Count;

Access first occurrence of any segment

Segment IN1 = message.DefaultSegment("IN1");

// OR

Segment IN1 = message.Segments("IN1")[0];

Accessing Fields

Access field values

string SendingFacility = message.GetValue("MSH.4");

// OR

string SendingFacility = message.DefaultSegment("MSH").Fields(4).Value;

// OR

string SendingFacility = message.Segments("MSH")[0].Fields(4).Value;

Check if field is componentized

bool isComponentized = message.Segments("PID")[0].Fields(5).IsComponentized;

// OR

bool isComponentized = message.IsComponentized("PID.5");

Check if field has repetitions

bool isRepeated = message.Segments("PID")[0].Fields(3).HasRepetitions;

// OR

bool isRepeated = message.HasRepetitions("PID.3");

Adding repeating field

var enc = new HL7Encoding();
Segment PID = new Segment("PID", enc);
Field f = new Field(enc);
f.HasRepetitions = true;

// Adding field f1 to f
Field f1 = new Field("A",enc);
f.AddRepeatingField(f1);

// Adding field f2 to f
Field f2 = new Field("B",enc);
f.AddRepeatingField(f2);

Get list of repeated fields

List<Field> repList = message.Segments("PID")[0].Fields(3).Repetitions();

Get particular repetition i.e 2nd repetition of PID.3

Field PID3_R2 = message.Segments("PID.3[2]");

// OR

Field PID3_R2 = message.Segments("PID.3(2)");

Update value of any field i.e. to update PV1.2 – patient class

message.SetValue("PV1.2", "I");

// OR

message.Segments("PV1")[0].Fields(2).Value = "I";

Access some of the required MSH fields with properties

string version = message.Version;
string msgControlID = message.MessageControlID;
string messageStructure = message.MessageStructure;

Generate ACKs

To generate an ACK message

Message ack = message.GetACK();

To generate negative ACK (NACK) message with error message

Message nack = message.GetNACK("AR", "Invalid Processing ID");

It may be required to change the application and facility fields

Message ack = message.GetACK();
ack.SetValue("MSH.3", appName);
ack.SetValue("MSH.4", facility);

⚠️ Take into account that a message shall be previously parsed before attempting to generate an ACK or NACK message.

Accessing Components

Access particular component i.e. PID.5.1 – Patient Family Name

string PatName1 = message.GetValue("PID.5.1");

// OR

string PatName1 = message.Segments("PID")[0].Fields(5).Components(1).Value;

Check if component is sub componentized

bool isSubComponentized = message.Segments("PV1")[0].Fields(7).Components(1).IsSubComponentized;

// OR

bool isSubComponentized = message.IsSubComponentized("PV1.7.1");

Update value of any component

message.Segments("PID")[0].Fields(5).Components(1).Value = "Jayant";

// OR

message.SetValue("PID.5.1", "Jayant");

Adding new Segment

// Create a Segment with name ZIB
Segment newSeg = new Segment("ZIB");
 
// Create Field ZIB_1
Field ZIB_1 = new Field("ZIB1");
// Create Field ZIB_5
Field ZIB_5 = new Field("ZIB5");
 
// Create Component ZIB.5.2
Component com1 = new Component("ZIB.5.2");
 
// Add Component ZIB.5.2 to Field ZIB_5
// 2nd parameter here specifies the component position, for inserting segment on particular position
// If we don’t provide 2nd parameter, component will be inserted to next position (if field has 2 components this will be 3rd, 
// If field is empty this will be 1st component
ZIB_5.AddNewComponent(com1, 2);
 
// Add Field ZIB_1 to segment ZIB, this will add a new filed to next field location, in this case first field
newSeg.AddNewField(ZIB_1);
 
// Add Field ZIB_5 to segment ZIB, this will add a new filed as 5th field of segment
newSeg.AddNewField(ZIB_5, 5);
 
// Add segment ZIB to message
bool success = message.AddNewSegment(newSeg);

New Segment would look like this:

ZIB|ZIB1||||ZIB5^ZIB.5.2

After evaluated and modified required values, the message can be obtained again in text format

string strUpdatedMsg = message.SerializeMessage();

Remove Trailing Components

var message = new Message();

// create ORC segment
var orcSegment = new Segment("ORC", new HL7Encoding());

// add fields
for (int eachField = 1; eachField <= 12; eachField++)
{
    orcSegment.AddEmptyField();
}

// add components to field 12
for (int eachField = 1; eachField < 8; eachField++)
{
    orcSegment.Fields(12).AddNewComponent(new Component(new HL7Encoding()));
}

// add values to components
orcSegment.Fields(12).Components(1).Value = "should not be removed";
orcSegment.Fields(12).Components(2).Value = "should not be removed";
orcSegment.Fields(12).Components(3).Value = "should not be removed";
orcSegment.Fields(12).Components(4).Value = ""; // should not be removed because in between valid values
orcSegment.Fields(12).Components(5).Value = "should not be removed";
orcSegment.Fields(12).Components(6).Value = ""; // should be removed because trailing
orcSegment.Fields(12).Components(7).Value = ""; // should be removed because trailing
orcSegment.Fields(12).Components(8).Value = ""; // should be removed because trailing

orcSegment.Fields(12).RemoveEmptyTrailingComponents();
message.AddNewSegment(orcSegment);

string serializedMessage = message.SerializeMessage(false);

Remove a Segment

Segments are removed individually, including the case where there are repeated segments with the same name

    // Remove the first segment with name NK1
    bool success = message.RemoveSegment("NK1") 

    // Remove the second segment with name NK1
    bool success = message.RemoveSegment("NK1", 1)

Encoded segments

Some contents may contain forbidden characters like pipes and ampersands. Whenever there is a possibility of having those characters, the content shall be encoded before calling the 'AddNew' methods, like in the following code:

var obx = new Segment("OBX", new HL7Encoding());

// Not encoded. Will be split into parts.
obx.AddNewField("70030^Radiologic Exam, Eye, Detection, FB^CDIRadCodes");  

// Encoded. Won't be parsed nor split.
obx.AddNewField(obx.Encoding.Encode("domain.com/resource.html?Action=1&ID=2"));

Copying a segment

The DeepCopy method allows to perform a clone of a segment when building new messages. Countersense, if a segment is referenced directly when adding segments to a message, a change in the segment will affect both the origin and new messages.

Segment pid = ormMessage.DefaultSegment("PID").DeepCopy();
oru.AddNewSegment(pid);

Null elements

Null elements (fields, components or subcomponents), also referred to as Present But Null, are expressed in HL7 messages as double quotes, like (see last field):

EVN|A04|20110613083617||""

Whenever requested individually, those elements are returned as null, rather than double quotes:

var expectEmpty = evn.Fields(3).Value; // Will return an empty string
var expectNull = evn.Fields(4).Value; // Will return null

Date Handling

A couple of date handling methods have been added, for parsing elements containing valid date/times, including time zones, as described in the HL7 standard. Examples:

// With time zone
string value1 = "20151231234500.1234+2358";
TimeSpan offset;
DateTime? dt1 = MessageHelper.ParseDateTime(value1, out offset);

// Date/time only
string value2 = "20151231234500";
DateTime? dt2 = MessageHelper.ParseDateTime(value2);

ParseDateTime will catch exceptions by default and return null in case of invalid dates. For preventing this mechanism, add an extra argument as true, like:

try
{
    var dt1 = MessageHelper.ParseDateTime(value1, out TimeSpan offse, true);
    var dt2 = MessageHelper.ParseDateTime(value2, true);
}
catch 
{
    // do something here
}

Credits

This is a fork from Jayant Singh's HL7 parser. Since then, it has been modified fundamentally, with respect to features, code quality, bugs and typos. For more information about the original implementation read:

The field encoding and decoding methods have been based on https://github.com/elomagic/hl7inspector

Breaking changes

Since version 2.9, the MSH segment will have an extra field at the beginning of the segment list, containing the field separator. This is according to the HL7 standard, as mentioned in Issue #26. Every field index in that segment should be increased by one.

Since version 2.9, some previously deprecated methods starting with lowercase have been removed. The replacement methods starting with uppercase shall be used instead.

Since version 2.21, message.GetValue() will decode the returned content.

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