View source for File column

{{Dynamics TOC}} {{WIP}}
File columns on Dataverse are a type of table column that can hold binary data. Since [[Releases/Spring_2023|release 16.0]], file columns can be also used in Resco mobile apps.  

== What are file columns ==

Dataverse introduced file columns in late 2019. They represent an alternative to traditional notes. Microsoft recommends using file columns for file sizes >5M. 

File is just another column type. Unlike conventional column types such as "Single line of text" (storing strings) or "Lookup" (storing reference to a CRM record), File columns store files. Files are stored in the Dataverse File Storage (actually in Azure) and not in Dataverse, i.e., they do not consume database space. (This applies for all types of attachments.)

Any number of file columns can be added to standard/custom tables. When adding a file column to a table, you can specify the maximum file size (default 32 MB, maximum 128 MB). This value cannot be changed later.

To learn more about this feature in Dataverse, see [https://learn.microsoft.com/en-us/power-apps/developer/data-platform/file-attributes?tabs=sdk Microsoft documentation].

== How are file columns supported in Resco mobile apps ==

In [[Releases/Spring_2023|release 16.0]], we have added basic support for File columns. 

{{Preview|In release 16.1 (available in the preview/beta channel), the support is improved:
* [[Releases/Summer_2023#Better_file_columns_support|Users can now create, modify, or delete the contents of file columns on entity forms in Resco mobile apps.]]
* [[Releases/Summer_2023#Reports|Reports can be saved into file column]].
* File columns are part of synchronization (allowing for full offline experience).
}}

;What is supported in Resco
* File and Filename fields are visible in Woodford. You can enable them in your projects.
** File field - This field must be enabled. It is represented as a lookup with a label and a clickable filename when added to a form.
** Filename field - This field is optional. When disabled and the File field is added to a form, the "Unknown" is displayed instead of the file name. This field is automatically enabled with the file field. We don't recommend disabling it.
: [[File:File column in woodford.png|600px]]
* You can use standard document operations such as print, export, and email.
* File fields are part of the synchronization process. The file is downloaded and cached when a user opens the field on the form. The next time the file is opened, it is loaded from local storage. When the file changes on the server, it is redownloaded when the user opens the field. This behavior is the same in both offline and online modes. This means a working internet connection is required when accessing the file for the first time.

;What is not supported
* Views - You cannot open the file from a view using commands (there is no OpenAttachment command). It can only be opened from form.
* Media tab - You cannot use the media tab to show files inline on the form (e.g., signature).
* Questionnaires - you cannot use files as storage for binary questions (image, signature).
* Form rules - It is impossible to access or modify file contents using form rules. 
* Resco JavaScript Bridge - it is not possible to get file content via JS bridge. You can access the raw values of both the File field and the Filename field. As a workaround, it is possible to use a file identifier (guid) in the File field to construct the download URL and download the content manually.

== File column versus annotation ==

In a sense, file columns are similar to conventional attachment entities - notes etc., except they are conceptually simpler to use. If you want to use annotations related to (say) accounts, you need to add a new relation annotation->account and use more complex UI - a media tab. (Images can use simpler image control.) If you need different notes (signature, image...) you have to organize multiple relations. In effect, the data schema gets more complex (in particular sync filters) which may negatively impact the performance.

File columns make most of these things simpler. If you need a 1:1 relation such as "product photo" or "PDF help file", you just add a File column to the table definition and a file control to the UI. No need to add a new relation or complicate sync filters, the life is simply easier. However, if you have N:1 relation (such as a variable number of images attached to an account record) File columns won't help - you have to use traditional note attachments instead.

Conclusions:
* As far the app creation is concerned, File columns are easier to work with. However, if you need true N:1 relations, you have to stick to annotations.
* File columns offer simpler security - row-level security of the record where they reside applies. Annotations are different: they are associated records (with specified cascading behavior).
* If you decide for file columns, expect weaker sync performance and only partially working filtering. This might become important if you use many attachments.
:(Resco has plans to optimize file column sync in the future, if this feature becomes more popular.)



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