View source for HowTos:Using BlobDownloadLink

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===== How to Use It =====
When you tag a ViewModelColumn with ''BlobDownloadLink=true,'' the UI will render this as a download link.

===== File Content =====
It will use a call to GetVMFile on the Turnkey server to allow for a download of content type application/octet-stream.

If your request has '''accept-encoding:gzip''' set - then we will gzip the file on the server before sending it back. 

===== Content Type =====
If your ViewModelColumn for data is "MyColumn" - and you add a ViewModelColumn called '''MyColumn_ContentType''' on the same ViewModel nesting (this need not be shown but must exist) - and that attribute is of type string - then the GetVMFile will use this content type when downloading the file (it must follow web standards https://www.sitepoint.com/mime-types-complete-list/). 

===== File Name =====
The ViewModelColumn that was tagged with BlobDownloadLink may be accompanied by a '''FileName''' column. '''Note!''' '''Case sensitive.''' 

If your tagged column was MyColumn - and you add a '''MyColumn_FileName''' on the same nesting (this need not be shown on screen but must exist in the ViewModel) - and that column is of type string - then the GetVMFile will mark the response as an attachment with a set file name.

Note that the filename is set during upload so this column needs to exist in the uploaded ViewModel.

===== Response Headers =====
The server will tag the response header when downloading like this:
 content-encoding:gzip
 content-length:16660
 content-type:application/octet-stream
The content length will in this case be the zipped length.

If you want control of exactly how the GetVMFile URL is formed, look at [[Documentation:The ExternalId explained|The ExternalId explained]].

See also [[Documentation:MVC_GetImage]]

{{Edited|July|12|2025}}


[[Category:Intermediate-Friendly]]
[[Category:Priority 50]]
[[Category:ViewModel fundamentals]]
[[Category:ViewModels and UI Modeling]]

[[Category:HowTos]]

[[Category:Development and Integration]]