c# - 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STOCKID声明了我的属性，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)]但这没有帮助

有什么建议么？

模型

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();


        }
    }

标签： c#visual-studioentity-frameworktsql

Answer 1

You should use [DatabaseGenerated(DatabaseGeneratedOption.None)] if you want to create they Keys yourself. [DatabaseGenerated(DatabaseGeneratedOption.Identity)] means, that you let the Database handle the Creation of the Primary Key. This is generally the best Option, because two instances of your Software trying to create the same Primary Key will result in an Error. This is an unlikely Scenario, but still: Let the Database create the Primary Keys. As you are using Database First, you do not have the Option to change the DatabaseGeneratedOption without updating your Database. If you created a Code First Model from Database, you do have the Option to change the DatabaseGeneratedOption, create a new Migration and Update the Database. But that may be undesirable, because Entity Framework might drop the entire Table and re-create it.

Please show the Code that creates the Entity added in stocks.LowFloatStocks.Add(stock);. Did you assign a value to Id? If so, try not to do that.

Otherwise, try the Solution suggested by @viveknuna in the Comments:

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