How to change the optype of "Device twin change events" frome client.

Hi Watson

1. You cann’t set opType from the device. opType is set by IoT Hub in the “device twin change event” payload to reflect what kind of operation changed the twin:
   • updateTwin ⇒ a partial update (PATCH) — e.g., when a device sends reported properties, or when a service does a partial twin update.
   • replaceTwin ⇒ a full replace (PUT) — e.g., when a service replaces the entire twin document.
2. From the C device SDK, you can only PATCH reported properties (which results in updateTwin). You cannot trigger replaceTwin from the device SDK. replaceTwin can be done by the service (via REST or a service SDK).

Update Twin

string deviceId = "myDevice";

// Retrieve current twin to get ETag
Twin twin = await registry.GetTwinAsync(deviceId);

// Build a JSON patch
string patchJson = @"{
  properties: {
    desired: {
      threshold: 25,
      telemetryIntervalSeconds: 30
    }
  },
  tags: {
    location: { region: 'US', site: 'Redmond' }
  }
}";

// Apply patch (ETag for optimistic concurrency)
Twin updated = await registry.UpdateTwinAsync(deviceId, patchJson, twin.ETag);
// => Emits opType = "updateTwin"

Replace twin

string replaceDesiredJson = @"{
  properties: {
    desired: {
      threshold: 10,
      telemetryIntervalSeconds: 5,
      mode: 'eco'
    }
  }
}";
Twin current = await registry.GetTwinAsync(deviceId);
Twin replacedDesired = await registry.UpdateTwinAsync(deviceId, replaceDesiredJson, current.ETag);

// Replace all tags
string replaceTagsJson = @"{
  tags: {
    location: { region: 'EU', site: 'Dublin' },
    owner: 'QuadrantResource'
  }
}";
Twin replacedTags = await registry.UpdateTwinAsync(deviceId, replaceTagsJson, replacedDesired.ETag);

// => Each of these PUT‑style replaces causes opType = "replaceTwin".

Hope it clarifies the situation.

Thank you.