element property by the SnapshotDb

[paprophet]

i use SimplePropertyGrid and can display the element property ,but i want select all elements property by the SnapshotDb in the end console.

[pmconne]

Can you please clarify your question? I don't understand what you're trying to achieve.

[paprophet]

in Command Line Applications (https://medium.com/itwinjs/writing-command-line-applications-with-imodel-js-ba06f4531cc2) ,
const _snapshotdb = SnapshotDb.openFile(bimfile);
let elementPropertys= _snapshotdb.elements.getElementProps('0x324');

i get the element property have two problem:
1.the element propertys donot have the categories/group
2.the element some property is id but not the value.

but in the frontend code ,in the PropertyGrid.tsx (
propertyData = await this.props.dataProvider.getData();
)
the propertyData is i want result,
so how i can get the same result by Command Line Applications Code!

[pmconne]

IModelDb.Elements.getElementProps gives you only the properties of a specific element - i.e., the properties that are stored directly on that element.
PropertyGrid.gatherData uses the EC presentation system to collect properties from potentially multiple elements and organize them into categories.
@grigasp may be able to tell you how to do the latter on the backend.

[grigasp]

The data provider interface on the frontend is specific to our React-based UI layer. The PresentationPropertyDataProvider implementation uses the Presentation API to retrieve the properties. As @pmconne already summarized, the presentation system collects properties of the element and its related elements and aspects.

The data provider interface is not available on the backend - you have to use the Presentation API directly. An example of that could be this (a little outdated) gist: https://gist.github.com/grigasp/aa75511dc4137137b651f56676c27f87. Have a look at listElementProperties function there.

Additionally, you might find this sample useful: https://www.itwinjs.org/sample-showcase/?group=Viewer+Features&sample=property-formatting-sample&imodel=Retail+Building+Sample, especially the "3. Do it yourself" approach.

[grigasp]

There are Presentation APIs on both sides - backend and frontend. The gist I linked is actually a backend-only example. However, you can use frontend examples as well, since APIs on both sides are very similar.

[paprophet]

thank you !
but there have 2 problem:
1.the Presentation.getManager().computeSelection(...) method is deprecated in new imodeljs version(2.10.0),so i want what method can replace of this old method?

2.when i set one elementid in this method ,the return value is right,but when i set elementarray in this method,the return value is not right(the return value is the same property in the element array, lost the diffent property)
so now i must set the element id one by one and read the property is slow .

[grigasp]

1. There are two overrides of that function - one is deprecated and the other is not.

2. The example passes the ContentFlags.MergeResults flag here, which, when selecting properties of multiple elements, merges values into one record. With that flag you always get one item in the resulting content set. If you don't pass the flag you should get a record per each element.

[paprophet]

thank you!
how to the unit change?
for example a property ( property name is 'Total Thickness' ) of the element value is '24' and 'unit' is m ,and displayvalue is '2400 mm'
so what method in imodeljs can change this (24 m to 2400 mm) ?

[grigasp]

Properties in ECSchemas define their kind of quantity, which in turn defines it's persistence and supported presentation units. From the information you gave it looks like 'm' is the persistence unit and presentation unit is 'mm'.

Currently we don't provide a way to choose between different presentation units of the same unit system when requesting content - the first unit of requested unit system is used. This means you would have to modify ECSchema to change presentation unit for the property from 'mm' to 'm' or something else in metric system. We do, however, allow choosing between different unit systems (imperial, metric, etc.), so if the property supports both imperial and metric, you can switch between them by passing appropriate value for the unitSystem attribute for content request props.

@ColinKerr, got anything more to add?