C＃实体框架-将数据插入子表中时堆栈溢出

Question

I am brand new to C# and Entity Framework. I have been used these tutorials and StackOverflow to give me a better understanding.

1. http://developer.telerik.com/featured/working-with-databases-through-visual-studio/
2. https://msdn.microsoft.com/en-us/data/jj193542

Using the Code-First approach, I have created a parent table and inserted data into the table no problem. When I had the parent table working correctly, I added the child table. I am now trying to insert data into that child table. However, I always get a stack overflow error. I think that there is something wrong with my mapping, but I am not sure what.

The following is my code. This is where I define the database context and the objects for the database.

public class DatabseContext : System.Data.Entity.DbContext
{
    public DbSet<Parent> Parents { get; set; }
    public DbSet<Child> Children { get; set; }
}

public class Parent
{
    private Guid parentIdVal;

    public Parent()
    {
        Children = new List<child>(); 
    }

    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public Guid parentId
    {
        get { return parentIdVal; }
        set { parentIdVal = Guid.NewGuid(); }
    }

    [Required]
    [StringLength(4)]
    public string parentData { get; set; }

    public virtual List<Child> Children { get; set; }
}

public class Child
{
    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public Guid childId
    {
        get { return childId; }
        set { childId = Guid.NewGuid(); }
    }

    [ForeignKey("Parent")]
    public Guid parentId { get; set; }

    [Required]
    [StringLength(65)]
    public string childData { get; set; }

    public virtual Parent Parent { get; set; }
}

I have a different class what parses a file and inserts rows into each table. This is the code:

    private static void addParentRecord(String source)
    {
        using (var db = new DatabaseContext())
        {
            Parent parent = new Parent(); 
            addDataToParent(parent); 

            createChildren(source, parent);
            db.Parents.Add(parent);
            db.SaveChanges();
        }
    }

    private static void createChildren(String source, Parent parent)
    {
        Regex regex = new Regex(pattern);
        foreach (Match match in regex.Matches(source))
        {
            Child child = new child();
            child.childData = match.Groups[group].Value; 
            parent.Children.Add(child); 
        }
    }

So the code creates both the parent and the child tables. It creates both the parent and the child objects and populates the objects. When I go to save the database changes, however, it continually calls the get ChildId and I get a stack overflow. There is some loop somewhere. I think it is because I don't have the parent-child mapping set up correctly.

Any help, pointers or links would be greatly appreciated. Thank you.

Answer 1

I figured it out. I did three things. I redid how I was creating the GUID, took out the lines DatabaseGenerated(DatabaseGeneratedOption.Identity) and I made sure that the ClassID method matched the class name with an Id added to the end(no extra 's or abbreviations). To anyone having the same problem, my code now looks like this:

public class Parent
{
  public Parent()
  {
    Children = new List<child>(); 
    parentId = Guid.NewGuid(); 
  }

  [Key]
  public Guid parentId { get; set; }

  [Required]
  [StringLength(4)]
  public string parentData { get; set; }

  public virtual List<Child> Children { get; set; }
}

public class Child
{
  public Child()
  {
   childId = Guid.NewGuid();
  }

  [Key]
  public Guid childId { get; set; }

  [ForeignKey("Parent")]
  public Guid parentId { get; set; }

  [Required]
  [StringLength(65)]
  public string childData { get; set; }

  public virtual Parent Parent { get; set; }
}