我試圖在實體框架中插入實體(使用代碼優先)時出現轉換異常。當我嘗試在實體框架中插入實體(使用代碼優先)時發生異常錯誤
演員的例外是像 「不可能投... Collection'1(實體)輸入(實體)」
從這個代碼:
public virtual T Insert(T entity)
{
return Context.Set<T>().Add(entity);
}
我想不通爲什麼。我很確定我做得很好。
郵政實體
public class Post
{
public long PostId { get; private set; }
public DateTime date { get; set; }
[Required]
public string Subject { get; set; }
public User User { get; set; }
public Category Category { get; set; }
[Required]
public string Body { get; set; }
public virtual ICollection<Tag> Tags { get; private set; }
public Post()
{
Category = new Category();
if (Tags == null)
Tags = new Collection<Tag>();
}
public void AttachTag(string name, User user)
{
if (Tags.Count(x => x.Name == name) == 0)
Tags.Add(new Tag {
Name = name,
User = user
});
else
throw new Exception("Tag with specified name is already attached to this post.");
}
public Tag DeleteTag(string name)
{
Tag tag = Tags.Single(x => x.Name == name);
Tags.Remove(tag);
return tag;
}
public bool HasTags()
{
return (Tags.Count > 0);
}
}
標籤實體
public class Tag
{
public long TagId { get; private set; }
public string Name { get; set; }
// Qui a ajouté le tag ?
public User User { get; set; }
}
映射
public class PostMap: EntityTypeConfiguration<Post>
{
public PostMap()
{
ToTable("Posts");
HasKey(x => x.PostId);
Property(x => x.Subject)
.HasColumnType("varchar")
.HasMaxLength(256)
.IsRequired();
Property(x => x.Body)
.HasColumnType("text")
.IsRequired();
HasMany(x => x.Tags);
HasOptional(x => x.Tags);
}
}
class TagMap : EntityTypeConfiguration<Tag>
{
public TagMap()
{
ToTable("Tags");
HasKey(x => x.TagId);
Property(x => x.Name)
.HasColumnType("varchar")
.HasMaxLength(256)
.IsRequired();
HasRequired(x => x.User);
}
}
感謝很多。
我對此沒有任何控制權。 – Rushino 2011-02-10 12:58:23