Insert multiple child records using linq to sql

Question

I'm creating a flick web application.

I have a flickrUser table and a flickrPhoto table

I've already inserted the flickrUser record and now i want to insert some flickrPhoto records;

FlickrPhoto:
 -photoid
 -flickruserid
 -id (PK)

here's how i'm trying to insert the flickrphoto records (flickrphoto is stored in MyPhoto table)

public void insertList(List<string> photoids, string flickruserid)
    {
        PicsPreciousLinqDataContext db = new PicsPreciousLinqDataContext();
        for (int i = 0; i < photoids.Count; i++)
        {              
                MyPhoto mf = new MyPhoto();
                mf.photoId = photoids[i];
                mf.source = "flickr";

                var query = from b in db.FlickrUsers
                            where b.nsid == flickruserid
                            select b;

                FlickrUser fUser = query.FirstOrDefault();
                mf.FlickrUserId = fUser.nsid;
                db.MyPhotos.InsertOnSubmit(mf);                
        }
        db.SubmitChanges();  <= Cannot add an entity with a key that is already in use.
    }

I've tried a few variations on this but also without success. What is the correct way to insert multiple child records?

Any help is appreciated.

Answer 1

Please check your MyPhotos Table, i suspect that it has the userId column as primary key . It should be foreign key/reference key column.

add the following instead your code,

 for (int i = 0; i < photoids.Count; i++)
    {              
            MyPhoto mf = new MyPhoto();
            mf.photoId = photoids[i];
            mf.source = "flickr";

            var query = from b in db.FlickrUsers
                        where b.nsid == flickruserid
                        select b;

            FlickrUser fUser = query.FirstOrDefault();
            mf.FlickrUserId = fUser.nsid;
            db.MyPhotos.Add(mf);               
    }
db.SubmitChanges();

Answer 2

If the value of id set by the database (ie NEWID() as default value, or auto-increment), then in your dbml designer, click on the column that's the primary key and ensure that the following properties have these values:

Auto Generated Value: True
Auto-Sync: OnInsert
Primary Key: True

If it is not set by the database, then instead of setting the first two properties above, you must create unique values for the Id column in your C# code for each row you insert.

This can be done with:

 Guid.NewGuid();

So in your code:

PicsPreciousLinqDataContext db = new PicsPreciousLinqDataContext();
...
MyPhoto mf = new MyPhoto();
            mf.photoId = photoids[i];
            mf.source = "flickr";
            mf.id = Guid.newGuid();
...
db.MyPhotos.InsertOnSubmit(mf);  

for columns that are uniqueIdentifier type columns in the database.