Question

我正在尝试使用EF Core将数据添加到数据库中，但是我无法克服重复的键错误：Cannot insert duplicate key row in object 'dbo.Stocks' with unique index 'IX_Stocks_Name'. The duplicate key value is (stock1).

我有一个实体Stock与Transaction一对多关系-一个Stock可以与许多Transaction相关。

仅当数据库中不存在具有给定ID的Stock时，问题才不会发生-在这种情况下，我可以添加许多具有相同Transaction的{{1}} ：

StockID

下面，我在类的using(var context = dbContextFactory.CreateDbContext(new string[0])) { List<Transaction> list = new List<Transaction>(); //If there's no Stock with ID "stock1" in the database the code works. //Executing the code for the second time results in error, however, if I changed stock1 to stock2 it would work var stock1 = new Stock("stock1"); list.AddRange(new Transaction[] { //I can add two exactly the same `Transaction`s and it's ok when executed on a fresh database new Transaction(stock1, DateTime.Now, 1M, 5), new Transaction(stock1, DateTime.Now, 1M, 5), }); context.Transactions.AddRange(list); context.SaveChanges(); }中添加了类的定义。

预先感谢您的提示。

IEntityTypeConfiguration类：

Transaction

public class Transaction { public Stock RelatedStock { get; set; } public DateTime TransactionTime { get; set; } public Decimal Price { get; set; } public int Volume { get; set; } public Transaction() { } }类：

TransactionConfiguration

public class TransactionConfiguration : IEntityTypeConfiguration<Transaction> { public void Configure(EntityTypeBuilder<Transaction> builder) { builder .ToTable("Transactions"); builder .Property<int>("TransactionID") .HasColumnType("int") .ValueGeneratedOnAdd() .HasAnnotation("Key", 0); builder .Property(transaction => transaction.Price) .HasColumnName("Price") .IsRequired(); builder .Property(transaction => transaction.TransactionTime) .HasColumnName("Time") .IsRequired(); builder .Property(transaction => transaction.Volume) .HasColumnName("Volume") .IsRequired(); builder .HasIndex("RelatedStockStockID", nameof(Transaction.TransactionTime)) .IsUnique(); } }类：

Stock

public class Stock { public string Name { get; set; } public ICollection<Transaction> Transactions { get; set; } public Stock() { } }类：

StockConfiguration

Answer 1

dbo.Stocks表上有一个唯一索引，名为IX_Stocks_Name。您违反了该索引。

您的问题是这一行：

var stock1 = new Stock("stock1");

您正在反复创建“ stock1”。相反，您应该首先为“ stock1”检索（或存储）Stock实体，并使用它（如果已经存在）。如果不存在，则可以安全地创建一个。

简而言之，代码使用现有的INSERT将dbo.Stocks插入Name。

Answer 2

您需要检查是否存在已知所需ID的库存。为了您的示例：

var stock1 = context.Stocks.SingleOrDefault(x => x.StockId == "stock1") ?? new Stock("stock1");

如果数据库中已有股票，它将与现有股票相关联；如果数据库中没有股票，则将与新股票相关联。

Answer 3

由于@ Zer0和@Steve Py的建议，我提出了以下解决方案：

void Insert(IEnumerable<Transaction> data)
        {
            using(var context = dbContextFactory.CreateDbContext(new string[0]))
            {
                List<Stock> stocks = data.Select(s => s.RelatedStock).Distinct(new StockComparer()).ToList();
                context.AddRange(stocks);
                context.SaveChanges();
                stocks = context.Stocks.ToList();

                List<Transaction> newList = new List<Transaction>(data.Count());

                foreach (var t in data)
                {
                        Stock relatedStock = stocks.Where(s => s.Name == t.RelatedStock.Name).First();
                        t.RelatedStock = relatedStock;
                        newList.Add(t);
                }

                context.Transactions.AddRange(newList);
                context.SaveChanges();
            }
        }

EF Core-在添加具有唯一索引的数据时出现重复键错误

3 个答案: