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POCan't save changes to child tables using LINQ to SQL that have foreign key constraints
 

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  1. POCan't save changes to child tables using LINQ to SQL that have foreign key constraints
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    <p>I am trying to teach myself LINQ to SQL and have decided to do a small MVC.NET project to get my feet wet. The problem is that I have fallen very early on with the following error.</p> <p>I am making a golf application so I have setup the database and got my dbml classes made. The database has a <code>course</code> table and a <code>hole</code> table. The <code>hole</code> table references the <code>courseId</code> by its primary key and has a foreigh key constraint on it. So all pretty standard.</p> <p>I have an MVC action on my controller that allows me to edit the course information (name, and hole info, for example, par and stroke index, etc.)</p> <p>When I do the save after an edit I get the following error.</p> <p>"<strong><em>An attempt was made to remove a relationship between a Course and a Hole. However, one of the relationship's foreign keys (Hole.CourseId) cannot be set to null</em></strong>."</p> <p>I have debugged this and can't see any problems. Is there something I need to do on the database to allow me to edit tables with foreign key constraints?</p> <p>Here is the action code:</p> <pre><code> [HttpPost] [ValidateInput(true)] public ActionResult Edit(int id, FormCollection collection) { var courseViewModel = new CourseViewModel { Course = _repository.GetCourse(id) }; if (courseViewModel.Course == null) { return View("NotFound", string.Format("Course {0} Not Found", id)); } try { UpdateModel(courseViewModel); _repository.SubmitChanges(); return RedirectToAction("Index", "Course"); } catch (Exception ex) { ModelState.AddRuleViolations(courseViewModel.Course.GetRuleViolations()); ModelState.AddModelError("", ex.Message); return View(courseViewModel); } } </code></pre> <p>Where _repository looks like this:</p> <pre><code> namespace Web.Repository { public class MyRepository { private MyDataContext db = new MyDataContext(); public void SubmitChanges() { db.SubmitChanges(); } public Course GetCourse(int id) { return db.Courses.SingleOrDefault(i =&gt; i.CourseId == id); } } } </code></pre>
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