Install-Package : 'EntityFramework.SQLite' already has a dependency defined for 'EntityFramework.Migrations'.

var user = db.Users.FirstOrDefault(x=>x.UserName == "hamid");

db.Post.Add(new Post
{
      Title = txtTitle.Text,
      Content = txtContent.Text,
      User = user
}
db.SaveChanges();

modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();

HasMany(x => x.Ads).WithRequired(x => x.User).WillCascadeOnDelete();

public IList<Post> Posts { set; get; }

public ICollection<Post> Posts { set; get; }