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LastWillAndTestament

The LastWillAndTestament class represents a Last Will and Testament message in the MQTT protocol. This message is sent by the broker on behalf of a client if the client disconnects unexpectedly. It contains details such as the topic, payload, Quality of Service (QoS), and other optional properties.

Constructors​

LastWillAndTestament(string topic, string payload, QualityOfService qos = QualityOfService.AtMostOnceDelivery, bool retain = false)​

Initializes a new instance of the LastWillAndTestament class with a UTF-8 encoded payload.

LastWillAndTestament(string topic, string payload, QualityOfService qos = QualityOfService.AtMostOnceDelivery, bool retain = false);

Parameters:

  • topic (string): The topic of the message.
  • payload (string): The payload in UTF-8 encoded format.
  • qos (QualityOfService): The QoS level (default: AtMostOnceDelivery).
  • retain (bool): Whether the message should be retained by the broker.

Example:

var lwt = new LastWillAndTestament("disconnect/topic", "Client disconnected", QualityOfService.AtLeastOnce, true);

LastWillAndTestament(string topic, byte[] payload, QualityOfService qos = QualityOfService.AtMostOnceDelivery, bool retain = false)​

Initializes a new instance of the LastWillAndTestament class with a binary payload.

LastWillAndTestament(string topic, byte[] payload, QualityOfService qos = QualityOfService.AtMostOnceDelivery, bool retain = false);

Parameters:

  • topic (string): The topic of the message.
  • payload (byte[]): The payload in binary format.
  • qos (QualityOfService): The QoS level (default: AtMostOnceDelivery).
  • retain (bool): Whether the message should be retained by the broker.

Example:

var lwt = new LastWillAndTestament("disconnect/topic", Encoding.UTF8.GetBytes("Client disconnected"), QualityOfService.ExactlyOnce, true);

Properties​

Topic​

Gets or sets the topic of the message.

string Topic { get; set; }

Example:

lwt.Topic = "status/update";

Payload​

Gets or sets the payload as a byte array.

byte[]? Payload { get; set; }

Example:

lwt.Payload = Encoding.UTF8.GetBytes("Disconnected");

PayloadAsString​

Gets or sets the payload as a UTF-8 encoded string.

string PayloadAsString { get; set; }

Example:

lwt.PayloadAsString = "Disconnected";

QoS​

Gets or sets the Quality of Service level.

QualityOfService QoS { get; set; }

Example:

lwt.QoS = QualityOfService.ExactlyOnce;

Retain​

Gets or sets whether the message should be retained by the broker.

bool Retain { get; set; }

Example:

lwt.Retain = true;

WillDelayInterval​

Gets or sets the delay before the Last Will and Testament is sent.

long? WillDelayInterval { get; set; }

Example:

lwt.WillDelayInterval = 60; // Delay of 60 seconds

MessageExpiryInterval​

Gets or sets the lifetime of the message in seconds.

long? MessageExpiryInterval { get; set; }

Example:

lwt.MessageExpiryInterval = 3600; // Expires in 1 hour

ContentType​

Gets or sets the content type of the payload.

string? ContentType { get; set; }

Example:

lwt.ContentType = "text/plain";

ResponseTopic​

Gets or sets the topic to which the client should publish a response.

string? ResponseTopic { get; set; }

Example:

lwt.ResponseTopic = "response/topic";

CorrelationData​

Gets or sets the correlation data for the message.

byte[]? CorrelationData { get; set; }

Example:

lwt.CorrelationData = Encoding.UTF8.GetBytes("correlation-id");

UserProperties​

Gets or sets a dictionary of user properties for the message.

Dictionary<string, string> UserProperties { get; set; }

Example:

lwt.UserProperties["key"] = "value";

Methods​

Validate()​

Validates the LastWillAndTestament instance for correctness.

bool Validate();

Exceptions:

  • HiveMQttClientException: Thrown if the topic or payload is invalid.

Example:

try
{
    lwt.Validate();
}
catch (HiveMQttClientException ex)
{
    Console.WriteLine($"Validation failed: {ex.Message}");
}