Answers

• allan Posts: 63,464Questions: 1Answers: 10,466 Site admin

  March 2022

  Hi,

  Are you using our .NET libraries to do the server-side data handling? If so, could you add .Debug(true) just before the .Process(...) call, and then show me the JSON return from the server when this error occurs? It will include the SQL that is being generated and executed.

  One possible workaround might be to use PreEdit and PreCreate on the server-side to detect when a null value is sent for either of those two fields, and if so, then set the field to not write to the database (editor.Field('name').Set(false);) - although that would cause an issue if you went from it having a value to it being null.

  Allan
• guidols Posts: 38Questions: 14Answers: 1

  April 2022 edited April 2022

  Yes, I'm using your libraries.

  If I have a row without a Project set, and try to modify the Status, this is the generated query:

  UPDATE [Main] SET [TaskStatus_Id] = @TaskStatus_Id, [Project_Id] = @Project_Id WHERE [Main].[Id] = @where_0

  So basically the library is trying to update both fields.

  So, should I implement PreEdit and PreCreate server-side? Need I to implement both?

  Another question at this point is: how can I "add" an empty option to a chosen field?

  Using chosen (but also using the select fields) is impossible to delete an existing entry, it's only possible to change it.
• allan Posts: 63,464Questions: 1Answers: 10,466 Site admin

  April 2022

  So, should I implement PreEdit and PreCreate server-side? Need I to implement both?

  Yes, both needed as assuming this can happen at both edit and create time.

  Something like:

              editor.PreCreate += (sender, e) => {
                  if (e.Values["Project_Id"] == null) {
                      editor.Field("Project_Id").Set(false);
                  }
               };
  

  However, as I mentioned, I'm a little concerned about that since you wouldn't be able to remove a value once it has been set.

  What we perhaps need to understand better here is why the Project_Id can't be set to null? Should that be valid in the schema?

  Another question at this point is: how can I "add" an empty option to a chosen field?

  With the select input you can use the placeholder, placeholderValue and placeholderDisabled options to enable an empty value and assign a specific value (typically null or an empty string) to it.

  With Chosen, looking at their documentation I don't see anything similar unfortunately. It looks like the list of options fed into it would need to include the empty value to be selectable.

  Allan
• guidols Posts: 38Questions: 14Answers: 1

  April 2022

  What we perhaps need to understand better here is why the Project_Id can't be set to null? Should that be valid in the schema?

  That's strange, as the fields are declared like that (for example):
  public Guid? Project_Id { get; set; }
• guidols Posts: 38Questions: 14Answers: 1

  April 2022

  I’m implemented PreCreate and this solves the problem.

  The fact is that now, as you correctly said, is not possible anymore to delete a value.

  Why the Guid? fields (declared in my model) are required by datatables? Should I declare somewhere that these fields are not required?
• guidols Posts: 38Questions: 14Answers: 1

  April 2022 edited April 2022

  Please note that with DateTime the behaviour is different; i.e., when trying to insert a null (or empty value):

  if the field is DateTime --> SQL error, can't insert NULL
  if the field is DateTime? --> OK

  With Guid the behaviour is different, and also is the error: is not something related to inserting a NULL value, but:

  Conversion failed when converting from a character string to uniqueidentifier
• allan Posts: 63,464Questions: 1Answers: 10,466 Site admin

  April 2022

  Ah - your model uses a DateTime? There isn't a direct representation of a DateTime in JSON, so it would need to become a string as noted in the docs here. I think that would apply to a guid as well since in practice it is just a 16 byte value that we tend to view with base16.

  Could you show me the SQL schema for your table that is giving the uniqueidentifier error please?

  Thanks,
  Allan
• guidols Posts: 38Questions: 14Answers: 1

  April 2022 edited April 2022

  Sure, here is the schema:

  CREATE TABLE [dbo].[Main](
  [Id] [int] IDENTITY(1,1) NOT NULL,
  [Target] [int] NULL,
  [Date] [datetime] NULL,
  [Project_Id] [uniqueidentifier] NULL,
  [Status_Id] [uniqueidentifier] NULL

  Seems also to me that the library:
  - Can convert strings to Datetime, even if a string is empty.
  - Can't convert a "NULL" string to a NULL guid, as the error is:

  Conversion failed when converting from a character string to uniqueidentifier.

  I see two problems here:
  - If I have, in the editor, a line with an empty project and if I modify, for instance, the target value; then also the "empty" project_id is sent to the server, ad described in my first comment.
  - This would not be a big issue, if the library would be able to convert the "NULL" to an empty guid. The problem is that it can't.

  Any possibility to fix this without the PreCreate workaround?

  Thanks!