从另一个表格插入数据后，EF6更新外键

Question

I'm trying to update a table's foreign key after I insert record from a different form.

Table Project :

ProjectID    CommentID

Table Comments :

CommentID   Date    Comment

First, I create the Project and assign CommentID a NULL value since there is no comment yet. So far so good.

Then, in some moment, I need to add a comment to my project. I can successfully add comments, but can't assign CommentID in related Project table.

This is how I'm trying to do (with no success):

MyEntities ctx = new MyEntities();

tblComents coment = new tblComments()
        {
            Date = DateComent.Value,
            Comment = TxtComment.Text.Trim()
        };

ctx.tblComments.Add(comment);
var projet = new tblProject { tblComments = comment };
ctx.SaveChanges();

Like this, I create the comment but the foreign key is never assigned in table Projects .

Any help?

Thanks

Answer 1

You are adding the comment to a new project that has nothing to do with your database:

  tblComents coment = new tblComents()
        {
            Date = DateComent.Value,
            Coment = TxtComent.Text.Trim()
        };
            tblProject project = ctx.tblProject(x=> x.Id == someid); // find the project you want
            if(project != null) project.tblComents.Add(coment);
ctx.SaveChanges();

You should either get a project from your database (code above) and then add the comment to that project, or add the project to database not the comment(code below):

  tblComents coment = new tblComents()
        {
            Date = DateComent.Value,
            Coment = TxtComent.Text.Trim()
        };
            tblProject project = new tblProject();
            ctx.tblProjects.Add(project);

            if(project != null) project.tblComents.Add(coment);
ctx.SaveChanges();