無法在表實體框架中插入標識列的顯式值

Question

我有一個在我的數據庫中存儲股票的表單，當我輸入一個股票時，它會保留信息，當我嘗試添加另一只股票時，我得到一個異常“無法為表中的標識列插入顯式值”

在我的 model 中，我聲明了我的STOCKID屬性，並在我的 T-SQL 中將其設置為IDENTITY(1,1) 。

在我的 model 中，我添加了[DatabaseGenerated(DatabaseGeneratedOption.Identity)]但這沒有幫助

有什么建議么？

Model

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)
);

添加庫存方法

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

如果您想自己創建密鑰，則應使用[DatabaseGenerated(DatabaseGeneratedOption.None)] 。 [DatabaseGenerated(DatabaseGeneratedOption.Identity)]意味着您讓數據庫處理主鍵的創建。 這通常是最好的選項，因為您的軟件的兩個實例嘗試創建相同的主鍵將導致錯誤。 這是一個不太可能的場景，但仍然：讓數據庫創建主鍵。 當您使用 Database First 時，您沒有在不更新數據庫的情況下更改DatabaseGeneratedOption的選項。 如果您從數據庫創建了 Code First Model，您可以選擇更改DatabaseGeneratedOption ，創建新的遷移和更新數據庫。 但這可能是不可取的，因為實體框架可能會刪除整個表並重新創建它。

請顯示創建在stocks.LowFloatStocks.Add(stock); . 您是否為Id分配了一個值？ 如果是這樣，盡量不要那樣做。

否則，請嘗試 @viveknuna 在評論中建議的解決方案：

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