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In our Syncfusion Xamarin demos, we have individual and common SampleBrowser samples. In individual sample browser, loaded only specific control samples, for example Popup, DataGrid, Chart, etc. In common / main SampleBrowser, loaded all the Xamarin controls along with its individual samples.
Regarding the mentioned condition code (COMMONSB), we have maintained different folder structure for images in the common SampleBrowser and individual SampleBrowser, so that handled with this condition to load images in the individual and common SampleBrowser.
In the latest updated SampleBrowser, we have removed this conditional code and it will be updated in our Volume 2 main release which is expected to available by end of this month June 2019.
We hope this helps. Please let us know, if you would require any further assistance.
Subburaj Pandian V