Why does a freeform metadata field behave differently in Sheet View vs. Metadata Dialog Boxes?

Question

I've recently begun migrating some documents that require a freeform "description" metadata field. I have this field defined as multi-line text with When I bring in a new document to my library and get SharePoint's dialog box to enter all the metadata fields, I get an error that the field has limit of 255 characters. Sure enough I have 318 characters in my description.

Same document in Datasheet view: I can copy/paste the exact same block of 318 characters for which I was getting an error into the appropriate row/column without any difficulty. When displaying the field, it's not truncated @ 255 characters, I can see all 318.

Is anyone aware of the reason the dialog box errors out but datasheet view allows the appropriate entry?

Answer 1

Multiline text is always stored in a column which allows "unlimited" text, but due to limitations in different versions of the office tools SharePoint by default limits it to 255 characters when used in a document library.

When modifying the properties using the SharePoint forms validation of this limitation works, but in Datasheet view it's a plugin that renders the grid using functionality from the Office client on the client PC. Depending on the version of that Office client the validation isn't in place, some of the erroneously allows too long texts.

If you want to be able to specify long texts, then you can specify "Allow unlimited length in document libraries" when you create (or edit) the column: