实体框架，删除和添加对象两次时InvalidOperationException

我使用实体框架6，数据库第一。

我有一个名为SubstanceNumbers的数据库表和一个数据网格，以及一个文本框和一些用于添加新条目的其他gui元素，SubstanceNumber有一个外键字段到Substance。

让我崩溃的场景是当我添加一个substanessubstance，删除它，添加它并再次删除它时，这不是最常见的用例，但我觉得它揭示了我所做的一些更大的错误。

My error message: System.InvalidOperationException was unhandled
Message=Saving or accepting changes failed because more than one entity of type 'SHMD_Edit.Models.EF.SubstanceNumber' have the same primary key value. Ensure that explicitly set primary key values are unique. Ensure that database-generated primary keys are configured correctly in the database and in the Entity Framework model. Use the Entity Designer for Database First/Model First configuration. Use the 'HasDatabaseGeneratedOption" fluent API or 'DatabaseGeneratedAttribute' for Code First configuration.

当我添加SubstanceNumbers时，我不想设置主键字段SubstanceNumberId，因为数据库应该处理自动递增，所以它将是0，直到我实际context.SaveChanges()。

我的添加/删除命令是这样的:

public RelayCommand AddSubstanceNumberCommand
    {
        get
        {
            return new RelayCommand(
                (x) =>
                {
                    var number = new SubstanceNumber();
                    number.SubstanceID = Id;
                    number.ModifiedBy = Main.op.LoginName;
                    number.ModifiedDate = DateTime.Now;
                    number.CreatedDate = DateTime.Now;
                    number.Type = Converters.NumberTypeToStringConverter.translation.First(t => t.Value == SelectedNewSubstanceNumberType).Key;
                    number.NumberText = Validator.Normalize(NewSubstanceNumber, SelectedNewSubstanceNumberType);
                    var temp = NewSubstanceNumber.Replace("-", "");
                    number.NumberValue = Int32.Parse(temp.Substring(0, temp.Length - 1));
                    if (NewSubstanceNumber != null && !SubstanceNumbers.Any(sn => sn.NumberText.Replace(" ", "") == number.NumberText && sn.Type == number.Type))
                        SubstanceNumbers.Add(number);
                    NewSubstanceNumber = "";
                }, param => this.CanAddSubstanceNumber);
        }
    }

和

public RelayCommand RemoveSubstanceNumberCommand
    {
        get
        {
            return new RelayCommand(
                (x) =>
                {
                    if (SelectedSubstanceNumber != null)
                    {
                        context.Entry(SelectedSubstanceNumber).State = EntityState.Deleted;
                        SubstanceNumbers.Remove(SelectedSubstanceNumber);
                    }
                });
        }
    }

My table:

Column name, Data Type, Allow Nulls (is identity, identity increment=1)
SubstanceNumberID   int Unchecked
SubstanceID int Unchecked
Type    int Unchecked
NumberText  char(16)    Unchecked
NumberValue int Unchecked
CreatedDate datetime    Unchecked
ModifiedDate    datetime    Unchecked
ModifiedBy  nvarchar(16)    Unchecked
RowVersion  timestamp   Unchecked

所以我假设上下文和我的substanenumbers列表之间有一些同步错误，但我看不出它是什么。你能指出来吗?

public virtual void Delete(T entity)
        {
            if (entity == null) throw new ArgumentNullException(typeof(T) + " cannot be null.");

            try
            {
                DbEntityEntry dbEntityEntry = _DbContext.Entry(entity);
                if (dbEntityEntry.State != EntityState.Deleted)
                {
                    dbEntityEntry.State = EntityState.Deleted;
                }
                else
                {
                    _DbSet.Attach(entity);
                    _DbSet.Remove(entity);
                }
            }
            catch (Exception ex)
            {
                    throw;
            }
        }