错误：db.SaveChanges上违反了多重约束？

Question

我是实体框架的新手。我用Entity Model创建了项目。当我试图将项目添加到表格时，它会出现错误“违反多重约束”这个想法吗？

表中的ID MAPPER是MAPS表中的FK。

代码背后：

private Mapper mMapper;
    if (mMapper.Id == 0)
                        db.Mappers.Add(mMapper);
                        db.SaveChanges();

 public partial class Mapper
    {
        public Mapper()
        {
            this.Maps = new HashSet<Map>();
        }

        public int Id { get; set; }
        public string Name { get; set; }
        public string RecordDelimiter { get; set; }
        public string ValueDelimiter { get; set; }
        public Nullable<int> ColumnDescriptionRow { get; set; }
        public Nullable<int> FirstRowOfData { get; set; }
        public Nullable<bool> IgnoreThisRecord { get; set; }
        public Nullable<bool> ExplodePartQuantity { get; set; }
        public Nullable<bool> IgnoreImportingErrors { get; set; }
        public Nullable<int> AngleMappingLeadingEdgeId { get; set; }
        public Nullable<int> AngleMappingTrailingEdgeId { get; set; }
        public string ValueWrapper { get; set; }
        public string ValueWrapperDelimiter { get; set; }

        public virtual AngleMapping AngleMapping { get; set; }
        public virtual AngleMapping AngleMapping1 { get; set; }
        public virtual ICollection<Map> Maps { get; set; }
    }

帮助感谢！