EF Core throws DbUpdateConcurrencyException when saving attached entities

Question

I wanted to update certain columns of the entity without loading entire entity into memory. Based on SO post i am trying to implement my logic. The suggested answer is using EF 4.1 but i am assuming same will work in EF Core. ( i am using EF Core)

There are more columns in the table but for brevity only few are displayed here

 [LearningDocuments]  
   LearningDocumentId (int),   
   LearningRequestID (int) (foriegnkey),  
   IsDone (bit),   
   CreatedDateTime (datetime),  
   ModifiedDateTime (dateTime)  
   VersionStamp (timestamp)   

Code to update certain columns

var dbContext = GetDBContext();

var documents = await dbContext.LearningDocuments
    .Where(x => x.LearningRequestID == 1234)
    .Select(x => new LearningDocument()
    {
        LearningDocumentId  = x.LearningDocumentId ,
        IsDone = x.IsDone,
        ModifiedDateTime = x.ModifiedDateTime
    })
    .ToListAsync()
    .ConfigureAwait(false);

documents.ForEach(d =>
{
    d.IsDone = true;
    d.ModifiedDateTime = DateTime.UtcNow;
    dbContext.LearningDocuments.Attach(d);
    dbContext.Entry(d).Property(x => x.IsDone).IsModified = true;
    dbContext.Entry(d).Property(x => x.ModifiedDateTime).IsModified = true;
});

await dbContext.SaveChangesAsync().ConfigureAwait(false);

However save changes is throwing exception:

Microsoft.EntityFrameworkCore.DbUpdateConcurrencyException : Database operation expected to affect 1 row(s) but actually affected 0 row(s). Data may have been modified or deleted since entities were loaded

LearningDocument is an entity. I am projecting the result into new LearningDocument instances selecting only required columns, is that okay?