无法在表实体框架中插入标识列的显式值

Question

我有一个在我的数据库中存储股票的表单，当我输入一个股票时，它会保留信息，当我尝试添加另一只股票时，我得到一个异常“无法为表中的标识列插入显式值”

在我的模型中，我声明了 STOCKID 属性，在我的 T-SQL 中，它设置为 IDENTITY(1,1)。

在我的模型中，我添加了[DatabaseGenerated(DatabaseGeneratedOption.Identity)]，但这并没有帮助

有什么建议吗？

型号

public class Stock
{
    #region Day 1's

    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]       
    public int Id { get; set; }

T-SQL

CREATE TABLE [dbo].[LowFloatStocks] 
(
    [Id]                   INT             IDENTITY (1, 1) NOT NULL,
    [Date]                 DATE            NOT NULL,
    [Ticker]               NVARCHAR (4)    NOT NULL,
    [PreviousClose]        DECIMAL (4, 2)  DEFAULT ((4.00)) NOT NULL,
    [PM_OpeningPrice]      DECIMAL (18, 2) DEFAULT ((3)) NOT NULL,
    [OpeningPrice]         DECIMAL (18, 2) NOT NULL,
    [PMFadePercent]        AS (ROUND(([OpeningPrice] - [PM_OpeningPrice]) / [PM_OpeningPrice], (4)) * (100.0)) PERSISTED NOT NULL,
    [GainPercent]          AS (ROUND(([High] - [OpeningPrice]) / [OpeningPrice], (4)) * (100.0)) PERSISTED NOT NULL,
    [GapPercent]           AS (ROUND(([OpeningPrice] - [PreviousClose]) / [PreviousClose], (4)) * (100.0)) PERSISTED NOT NULL,
    [Spike]                DECIMAL (18, 2) NOT NULL,
    [1stSpike%]            AS (ROUND(([Spike] - [OpeningPrice]) / [OpeningPrice], (4)) * (100.0)) PERSISTED NOT NULL,
    [High]                 DECIMAL (18, 2) NOT NULL,
    [HighPercent]          AS (ROUND(([High] - [PreviousClose]) / [PreviousClose], (4)) * (100.0)) PERSISTED NOT NULL,
    [Low]                  DECIMAL (18, 2) NOT NULL,
    [LowPercent]           AS (ROUND(([Low] - [PreviousClose]) / [PreviousClose], (4)) * (100.0)) PERSISTED NOT NULL,
    [Close]                DECIMAL (18, 2) DEFAULT ((4)) NOT NULL,
    [ClosePercent]         AS              (round(([Close]-[PreviousClose])/[PreviousClose],(4))*(100.0)) PERSISTED NOT NULL,
    [ClosevHigh]           AS              (round(([High]-[Close])/[Close], (4))*(100)) PERSISTED NOT NULL,
    [ClosevOpen]           AS              (round(([OpeningPrice]-[Close])/[OpeningPrice],(4))*(100.0)) PERSISTED NOT NULL,
    [CloseLessEqualToOpen] AS              (CONVERT([nchar](3),case when [Close]<=[OpeningPrice] then 'Yes' else 'No' end)) PERSISTED NOT NULL,
    [CloseRed]             AS              (CONVERT([nchar](3),case when [Close]<[OpeningPrice] then 'Yes' else 'No' end)) PERSISTED NOT NULL,
    [Catalyst]             NVARCHAR (50)   NOT NULL,
    [Float]                DECIMAL (18, 3) NOT NULL,
    [Dilution]             NCHAR (3)       NOT NULL,

    PRIMARY KEY CLUSTERED ([Id] ASC)
);

添加库存方法

public ICommand AddCommand => _addCommand ?? (_addCommand = new RelayCommand(param => this.AddStock()));


    #endregion 

    #region Actions

    private void AddStock()
    {
        using (var stocks = new AppDbContext())
        {
            stocks.LowFloatStocks.Add(stock);
            stocks.SaveChanges();
            Stocks = stocks.LowFloatStocks.ToList();
            Clear();


        }
    }

Answer 1

如果您想自己创建密钥，您应该使用[DatabaseGenerated(DatabaseGeneratedOption.None)]。 [DatabaseGenerated(DatabaseGeneratedOption.Identity)] 表示您让数据库处理主键的创建。这通常是最佳选项，因为您的软件的两个实例尝试创建相同的主键将导致错误。这是一个不太可能的场景，但仍然：让数据库创建主键。当您使用 Database First 时，您没有在不更新数据库的情况下更改 DatabaseGeneratedOption 的选项。如果您从数据库创建了 Code First 模型，则可以选择更改 DatabaseGeneratedOption、创建新的迁移和更新数据库。但这可能是不可取的，因为实体框架可能会删除整个表并重新创建它。

请显示创建在stocks.LowFloatStocks.Add(stock); 中添加的实体的代码。你给Id赋值了吗？如果是这样，请尽量不要这样做。

否则，请尝试@viveknuna 在评论中建议的解决方案：

stock.Id = 0; 
stocks.LowFloatStocks.Add(stock); 
stocks.SaveChanges();