我将 Entity Framework 4.1 与 MVC 3 一起使用。
我遇到的问题是,当我将带有附加类别的新问题保存到数据库时,它应该只更新 Question 和 QuestionCategories 表,但是它会在 Category 表中添加一个新的重复条目。
public class Question{
public int QuestionId{ get; set; }
public string QuestionName { get; set;}
public virtual IList<Category> Categories{ get; set; }
}
public class Category{
public int CategoryId{ get; set; }
public string CategoryName { get; set; }
}
modelBuilder.Entity<Question>()
.HasMany(e => e.Categories)
.WithMany() // don't need?
.Map(mc => mc
.ToTable("QuestionCategories")
.MapLeftKey("QuestionId")
.MapRightKey("CategoryId"));
public long CreateQuestion(Question question)
{
this.repository.questions.Add(question);
this.repository.SaveChanges();
return question.Id;
}
public void AddCategoryToQuestion(question question, List<long> CategoryIds)
{
if (question.Categories == null)
question.Categories = new List<Category>();
foreach (long CategoryId in CategoryIds)
{
if (question.Categories.FirstOrDefault(q => q.Id == CategoryId) == null)
{
Category category = this.CategoryService.GetCategoryById(CategoryId);
if (category != null)
{
question.Categories.Add(category);
}
}
}
}
public void SaveQuestion(Question Question)
{
this.repository.Questions.Attach(Question);
this.repository.SetModified(Question);
this.repository.SaveChanges();
}
Category Table
Before SaveQuestion runs when user assigns Operations Category to a new question.
CategoryId CategoryName
1 Operations
2 Safety
After SaveQuestion runs
CategoryId CategoryName
1 Operations
2 Safety
3 Operations
先感谢您。