在 EF 中删除和保存更改时出现 DbUpdateException

Question

我试图通过简单地使用 db.'table'.remove('object') 来删除数据库中的记录，但是在调用 db.SaveChanges() 时会抛出异常。

'在EntityFramework.dll中发生'System.Data.Entity.Infrastructure.DbUpdateException'类型的异常，但未在用户代码中处理'

我在控制器中的删除方法

public ActionResult Delete(int? id)
{
    if (id == null)
    {
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }
    Customer customer = db.Customers.Find(id);
    if (customer == null)
    {
        return HttpNotFound();
    }
    db.Customers.Remove(customer);
    db.SaveChanges();

    return RedirectToAction("Index");
}

型号：

public class Customer
{
    [Key, ForeignKey("User")]
    public int UserId { get; set; }
    public string Email { get; set; }
    public virtual CreditCard CreditCard { get; set; }
    public virtual ShoppingCart ShoppingCart { get; set; }
    public virtual List<Enquiry> Enquiries { get; set; }
    public virtual List<Order> Orders { get; set; }
    public virtual User User { get; set; }
}
public class User
{
    [Key]
    public int Id { set; get; }
    public string Username { set; get; }
    public string Password { set; get; }
    public string FirstName { set; get; }
    public string Surname { set; get; }
    public virtual UserRole UserRole { get; set; }
}

public class ShoppingCart
    {
        [Key, ForeignKey("Customer")]
        public int Id { get; set; }
        public virtual List<CartItem> CartItems { get; set; }
        public virtual Customer Customer { get; set; }
    }

部分例外：

A DbUpdateException was caught while saving changes. Type: Customer_8D9A6B7F7D247C9CB9F95E830039791E299E94FC91841FD33610DD1804AEF739 was part of the problem. 

完全例外：

System.Data.Entity.Infrastructure.DbUpdateException: An error occurred while updating the entries. See the inner exception for details. ---> System.Data.Entity.Core.UpdateException: An error occurred while updating the entries. See the inner exception for details. ---> System.Data.SqlClient.SqlException: The DELETE statement conflicted with the REFERENCE constraint "FK_dbo.ShoppingCarts_dbo.Customers_Id". The conflict occurred in database "MVC_COMP1562.Models.SchemaDBContext", table "dbo.ShoppingCarts", column 'Id'.
The statement has been terminated.
   at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.SqlInternalConnection.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.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString, Boolean isInternal, Boolean forDescribeParameterEncryption)
   at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async, Int32 timeout, Task& task, Boolean asyncWrite, Boolean inRetry, SqlDataReader ds, Boolean describeParameterEncryptionRequest)
   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry)
   at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, String methodName, Boolean sendToPipe, Int32 timeout, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry)
   at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
   at System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher.<NonQuery>b__0(DbCommand t, DbCommandInterceptionContext`1 c)
   at System.Data.Entity.Infrastructure.Interception.InternalDispatcher`1.Dispatch[TTarget,TInterceptionContext,TResult](TTarget target, Func`3 operation, TInterceptionContext interceptionContext, Action`3 executing, Action`3 executed)
   at System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher.NonQuery(DbCommand command, DbCommandInterceptionContext interceptionContext)
   at System.Data.Entity.Internal.InterceptableDbCommand.ExecuteNonQuery()
   at System.Data.Entity.Core.Mapping.Update.Internal.DynamicUpdateCommand.Execute(Dictionary`2 identifierValues, List`1 generatedValues)
   at System.Data.Entity.Core.Mapping.Update.Internal.UpdateTranslator.Update()
   --- End of inner exception stack trace ---
   at System.Data.Entity.Core.Mapping.Update.Internal.UpdateTranslator.Update()
   at System.Data.Entity.Core.EntityClient.Internal.EntityAdapter.<Update>b__2(UpdateTranslator ut)
   at System.Data.Entity.Core.EntityClient.Internal.EntityAdapter.Update[T](T noChangesResult, Func`2 updateFunction)
   at System.Data.Entity.Core.EntityClient.Internal.EntityAdapter.Update()
   at System.Data.Entity.Core.Objects.ObjectContext.<SaveChangesToStore>b__35()
   at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)
   at System.Data.Entity.Core.Objects.ObjectContext.SaveChangesToStore(SaveOptions options, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction)
   at System.Data.Entity.Core.Objects.ObjectContext.<>c__DisplayClass2a.<SaveChangesInternal>b__27()
   at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func`1 operation)
   at System.Data.Entity.Core.Objects.ObjectContext.SaveChangesInternal(SaveOptions options, Boolean executeInExistingTransaction)
   at System.Data.Entity.Core.Objects.ObjectContext.SaveChanges(SaveOptions options)
   at System.Data.Entity.Internal.InternalContext.SaveChanges()
   --- End of inner exception stack trace ---
   at System.Data.Entity.Internal.InternalContext.SaveChanges()
   at System.Data.Entity.Internal.LazyInternalContext.SaveChanges()
   at System.Data.Entity.DbContext.SaveChanges()
   at MVC_COMP1562.Controllers.CustomersController.Delete(Nullable`1 id) in C:\Users\kacpe\Documents\Visual Studio 2015\Projects\MVC_COMP1562\MVC_COMP1562\Controllers\CustomersController.cs:line 165

Answer 1

您似乎有另一个名为 dbo.ShoppingCarts 的关于购物车的表，其中包含与您要删除的客户相关的一行或多行。
因此，首先您必须删除与该客户相关的行，然后您才能删除该客户。发生这种情况是因为客户 ID 是该其他表中的外键。
如果情况并非如此，请将您的 ShoppingCarts 类添加到问题中。