EPiServer 11: Convert media type programatically

Has anyone attempted to convert a media file type programmatically in EPiServer?

We have a type we modeled for images, ImageFile, and a type that was added via a plugin. We don't use the type added by the plugin but found that images uploaded will, from time to time, be created as the wrong type. I am hoping to figure out how to make the conversion so I can run a scheduled job to batch convert them all then remove the plugin.

So far, I can programmatically make a copy of A as type B then delete A. What I would really like to do is convert A to B for a seamless transition.

First thing I tried is cloning the image as the proper type but that comes up null

var media = _contentRepository.Service.GetDescendents(SiteDefinition.Current.GlobalAssetsRoot)
                .Where(i => _contentRepository.Service.Get<IContent>(i) is MediaData);
var imageFileTypeId = new ImageFile().ContentTypeID;
foreach (var img in media)
{
    if (img.Get<IContent>() is GcEpiImageFile)
    {
         count++ // for summary
         var item = _contentLoader.Service.Get<GcEpiImageFile>(img.Get<IContent>().ContentLink);
         var cloneItem = item.CreateWritableClone() as ImageFile;
         if (cloneItem == null) 
         {
             var msg = $"{item.Name}: {item.ContentLink.ID} came up null";
             OnStatusChanged(msg);
             summaryMessage.AppendLine(msg);
             continue;
         }
         cloneItem.ContentTypeID = imageFileTypeId;
         _contentRepository.Service.Save(cloneItem, SaveAction.Publish, AccessLevel.NoAccess);

    }

Next thing I tried is cloning it as the base class ImageData which seems to create the object but throws a Object reference not set to an instance of an object exception when saving.

var media = _contentRepository.Service.GetDescendents(SiteDefinition.Current.GlobalAssetsRoot)
                .Where(i => _contentRepository.Service.Get<IContent>(i) is MediaData);
var imageFileTypeId = new ImageFile().ContentTypeID;
foreach (var img in media)
{
    if (img.Get<IContent>() is GcEpiImageFile)
    {
         count++ // for summary
         var item = _contentLoader.Service.Get<GcEpiImageFile>(img.Get<IContent>().ContentLink);
         var cloneItem = item.CreateWritableClone() as ImageData;
         if (cloneItem == null) 
         {
             var msg = $"{item.Name}: {item.ContentLink.ID} came up null";
             OnStatusChanged(msg);
             summaryMessage.AppendLine(msg);
             continue;
         }
         try
         { 
             cloneItem.ContentTypeID = imageFileTypeId;
         }
         catch (Exception ex)
         {
             summaryMessage.AppendLine($"exception triggered by id assignment {ex.Message}<br />{ex.InnerException}");
         }
         try
         { 
             _contentRepository.Service.Save(cloneItem, SaveAction.Publish, AccessLevel.NoAccess);
         }
         catch (Exception ex)
         {
             summaryMessage.AppendLine(
                            $"exception triggered by save {ex.Message}<br />{ex.InnerException}");
         }
    }

here is my stack trace:

Object reference not set to an instance of an object.
at EPiServer.Validation.Internal.RoutingSegmentValidator.Validate(IContent instance) at

EPiServer.Validation.Internal.ContextValidatorWrapper`2.Validate(Object instance, Object context) 

at EPiServer.Validation.Internal.ValidationService.ValidateRecursively(Object instance, Object context, HashSet`1 visitedInstances) 

at EPiServer.Validation.Internal.ValidationService.Validate[T](Object instance, T context) 

at EPiServer.Core.ContentProvider.Validate(IContent content, ContentSaveValidationContext saveValidationContext) 

at EPiServer.Core.Internal.DefaultContentRepository.Save(IContent content, SaveAction action, AccessLevel access) at Web.Business.ScheduledJobs.ImageConversion.Execute()

Any thoughts, help, guidance would be greatly appreciated

Solution

Hat tip to Johann Kronberg on the EPiServer developer forum for his help.

BEGIN TRANSACTION [ConvertTransaction]
BEGIN TRY
  DECLARE @FromPropertyID1 int
  DECLARE @ToPropertyID1 int
  DECLARE @FromPropertyID2 int
  DECLARE @ToPropertyID2 int
  DECLARE @FromPropertyID3 int
  DECLARE @ToPropertyID3 int

  DECLARE @RC int
  DECLARE @PageID int
  DECLARE @FromPageType int
  DECLARE @ToPageType int
  DECLARE @Recursive bit
  DECLARE @IsTest bit

  SELECT @PageID = 1
#get your type ids from content type guid
  SELECT @FromPageType = pkID FROM tblContentType WHERE ContentTypeGUID = 'guid of the media type being changed'
  SELECT @ToPageType = pkID FROM tblContentType WHERE ContentTypeGUID = 'guid of the media type it is being change to'


#mapping properties THIS IS IMPORTANT!!!

  SELECT @FromPropertyID1 = pkID FROM tblPropertyDefinition WHERE fkContentTypeID = @FromPageType AND [Name] = 'Copyright'
  SELECT @FromPropertyID2 = pkID FROM tblPropertyDefinition WHERE fkContentTypeID = @FromPageType AND [Name] = 'Description'
  SELECT @FromPropertyID3 = pkID FROM tblPropertyDefinition WHERE fkContentTypeID = @FromPageType AND [Name] = 'Notes'

  SELECT @ToPropertyID1 = pkID FROM tblPropertyDefinition WHERE fkContentTypeID = @ToPageType AND [Name] = 'Copyright'
  SELECT @ToPropertyID2 = pkID FROM tblPropertyDefinition WHERE fkContentTypeID = @ToPageType AND [Name] = 'Alt Text'
  SELECT @ToPropertyID3 = pkID FROM tblPropertyDefinition WHERE fkContentTypeID = @ToPageType AND [Name] = 'Notes'

  SET @Recursive = 1
  SET @IsTest = 0

  print @PageID
  print @FromPageType
  print @ToPageType

  DECLARE @MasterLanguageID int

  SET @MasterLanguageID = 8

  EXECUTE @RC = [dbo].[netConvertPropertyForPageType]
     @PageID
    ,@FromPageType
    ,@FromPropertyID1
    ,@ToPropertyID1
    ,@Recursive
    ,@MasterLanguageID
    ,@IsTest

  print @RC

  EXECUTE @RC = [dbo].[netConvertPropertyForPageType]
     @PageID
    ,@FromPageType
    ,@FromPropertyID2
    ,@ToPropertyID2
    ,@Recursive
    ,@MasterLanguageID
    ,@IsTest

  print @RC

  EXECUTE @RC = [dbo].[netConvertPropertyForPageType]
     @PageID
    ,@FromPageType
    ,@FromPropertyID3
    ,@ToPropertyID3
    ,@Recursive
    ,@MasterLanguageID
    ,@IsTest

  print @RC

  EXECUTE @RC = [dbo].[netConvertPageType]
     @PageID
    ,@FromPageType
    ,@ToPageType
    ,@Recursive
    ,@IsTest

  print @RC

  COMMIT TRANSACTION [ConvertTransaction]
END TRY
BEGIN CATCH
  ROLLBACK TRANSACTION [ConvertTransaction]
END CATCH

-- Run separately
DECLARE @FromPageType int
SELECT @FromPageType = pkID FROM tblContentType WHERE ContentTypeGUID = '0a89e464-56d4-449f-aea8-2bf774ab8730'
EXECUTE netContentTypeDelete @ContentTypeID = @FromPageType

Note If your source type has more properties than your destination type you may need to add properties to your destination. In my first run at this, I was able to convert the types but I could not delete the destination type.