Add file to MediaField

[vitalybrandes]

I am programmably update ContentItem with adding file to MediaField.

 var result = await _contentManager.GetAsync(ContentItemId);
 if (result != null)
{
     result.Alter<Printer>(nameof(Printer), part =>
     {
         part.BackupFile = new MediaField { Paths = new string[] { FilePath } };
     });
     await _contentManager.UpdateValidateAndCreateAsync(result, VersionOptions.Published);
}

Actually, i found that that this replace the existing data from part.BackupFile to new one, instead add.
the BackupFile in Media Filed with Multiple files allowed.

What i am doing wrong?

[lampersky]

part.BackupFile = new MediaField { Paths = new string[] { FilePath } };
This line replaces current Paths value, with single item array.
Maybe try to read Paths first, append additional item and save it back.