How to concatenate a byte array into an existing one inside a Database

Question

I have some LinqToSQL objects. One of those has a 'Binary' column, I think it's VarBinary(max) on SQL.

Every now and then I need to add/concatenate a byte array into that column for a certain row. This is how I do it:

void StoreBytesInDb(IEnumerable<byte> bytesToStore)
    {
        using (var dataBaseContext = new MyDataClasses(DatabaseInfo.ConnectionString))
        {
            if (this.currentObjectId == -1)
            {
                this.NewObjectToDatabase();
                this.currentSavedBytes = new List<byte>();
            }

            this.CurrentObject = dataBaseContext.Objects.Single(e => e.Id_Object == this.currentObjectId);

            this.currentSavedBytes.AddRange(bytesToStore);
            this.CurrentObject.Bytes_Data = this.currentSavedBytes.ToArray();

            dataBaseContext.SubmitChanges();
        }
    }

So, as you can see:

1. I use Linq to "AddRange" into the saved bytes (in the heap).
2. Then I put it into the right column in the object.
3. Submit Changes.

At low speeds it works.

The problem appears when I speed it up to several times per second. Sometimes it throws a 'System.ArgumentException' saying: "An item with the same key has already been added." The exact line that throws the exception is:

this.CurrentObject.Bytes_Data = currentSavedBytes.ToArray();

Any tips on how to improve this?

Answer 1

If it's larger byte data you're dealing with - maybe move it out of Db , keep a ref onto File System - and append there - which is better.

On the other thing - just an idea...

currentSavedBytes - why you keep that as a member? may be a concurency issue (if sharing) - try moving that in the scope of the method.

Answer 2

None of this is optimal.

1. You should not store big files in the database
2. Linq 2 Sql is not optimized to do it
3. Also, it~s not a good idea to handle files all at once in memory - they might be big and you get and OOM exception

I would suggest you to:

1. Save the files somewhere else like @NSGaga said in his comment
2. If you must save in the database at least use a FileStream column (which is pretty much saving into the database disk).
3. Do it like explained in this article so you are able to append to the file