[英]Conflict between FK an PK Entity Framework Core
我正在嘗試使用 Entity Framework 核心構建一個 web 應用程序,我創建了兩個模型Category
an Pie
,我做了所有事情,包括 DbContext 依賴注入,我創建了一個DbInializer
類來檢查數據庫是否為空,如果這是真的將插入一些數據,問題是當我運行應用程序時出現異常,好像類別表中的主鍵和 Pies 表中的外鍵之間存在沖突,這是異常:
System.Data.SqlClient.SqlException: The MERGE statement conflicted with the FOREIGN KEY constraint "FK_Pies_Categories_CategoryId".The conflict occurred in database "ShopDb", table "dbo.Categories", column 'CategoryId'.
at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean & dataReady)
at System.Data.SqlClient.SqlDataReader.TryHasMoreRows(Boolean & moreRows)
at System.Data.SqlClient.SqlDataReader.TryHasMoreResults(Boolean & moreResults)
at System.Data.SqlClient.SqlDataReader.TryNextResult(Boolean & more)
at System.Data.SqlClient.SqlDataReader.NextResult()
at Microsoft.EntityFrameworkCore.Update.AffectedCountModificationCommandBatch.Consume(DbDataReader reader)
ClientConnectionId: 775a7294 - 531a - 44cc - 8fbc - 29d293c339d5
Error Number: 547,State: 0,Class: 16}
這是 Pie 類:
public class Pie
{
public int PieId { get; set; }
public string Name { get; set; }
public string ShortDescrition { get; set; }
public string LongDescription { get; set; }
public string AllegryInformation { get; set; }
public string ImageUrl { get; set; }
public string ImageThumbnailUrl { get; set; }
public bool IsPieOfTheWeek { get; set; }
public bool InStock { get; set; }
public decimal Price { get; set; }
public int CategoryId { get; set; }
public virtual Category Category { get; set; }
}
...這里是類別類:
public class Category
{
public int CategoryId { get; set; }
public string CategoryName { get; set; }
public string Description { get; set; }
public List<Pie> Pies { get; set; }
}
Startup類的Configure方法:
public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
app.UseDeveloperExceptionPage();
app.UseStatusCodePages();
app.UseStaticFiles();
app.UseMvcWithDefaultRoute();
DbInitializer.Seed(app);
}
DbInitializer 類:
public class DbInitializer
{
public static void Seed(IApplicationBuilder applicationBuilder)
{
AppDbContext context = applicationBuilder.ApplicationServices.GetRequiredService<AppDbContext>();
if (!context.Categories.Any())
{
context.AddRange(
new Category { CategoryName = "First Pie", Description="Descriptionslqdfq vdfhsqdqsdhfs qsdhf" },
new Category { CategoryName = "Cheese Cackes", Description = "Descriptionslqdfq vdfhsqdqsdhfs qsdhf" },
new Category { CategoryName = "Saesonal Pie", Description = "Descriptionslqdfq vdfhsqdqsdhfs qsdhf" });
}
if (!context.Pies.Any())
{
context.AddRange(new Pie { Name = "Apple Pie", ShortDescrition = "short description", LongDescription = "Long description", AllegryInformation = "sflqjq", ImageUrl = "#", IsPieOfTheWeek = true, InStock = true, Price = 15.65M },
new Pie { Name = "Apple Pie", ShortDescrition = "short description", LongDescription = "Long description", AllegryInformation = "sflqjq", ImageUrl = "#", IsPieOfTheWeek = true, InStock = true, Price = 15.65M },
new Pie { Name = "Apple Pie", ShortDescrition = "short description", LongDescription = "Long description", AllegryInformation = "sflqjq", ImageUrl = "#", IsPieOfTheWeek = true, InStock = true, Price = 15.65M },
new Pie { Name = "Apple Pie", ShortDescrition = "short description", LongDescription = "Long description", AllegryInformation = "sflqjq", ImageUrl = "#", IsPieOfTheWeek = true, InStock = true, Price = 15.65M },
new Pie { Name = "Apple Pie", ShortDescrition = "short description", LongDescription = "Long description", AllegryInformation = "sflqjq", ImageUrl = "#", IsPieOfTheWeek = true, InStock = true, Price = 15.65M });
}
context.SaveChanges();
}
}
這是因為你添加了
public int CategoryId { get; set; }
在pie
實體框架在您添加時自行處理關系
public virtual Category Category { get; set; }
在您的情況下,當您添加CategoryId
它需要categoryId
因為它沒有設置為 null 這就是為什么它給出異常,因此您可以將CategoryId
設置為nullable int
public int? CategoryId { get; set; }
或者您可以讓實體框架將其作為nullable
為您處理
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