MVC 与 EF 关系数据库映射
本文关键字：映射 关系数据库 EF MVC | 更新日期: 2023-09-27 18:37:04
当我尝试更新数据库以填充我的表时，我遇到了此错误。
PM>更新数据库
No pending explicit migrations.
Running Seed method.
System.InvalidOperationException: Sequence contains no matching element
at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source, Func`2 predicate)
at RecreationServicesTicketingSystem.Migrations.Configuration.Seed(IssueContext context) in C:'Users'jwan'Documents'Visual Studio 2012'Projects'RecreationServicesTicketingSystem'RecreationServicesTicketingSystem'Migrations'Configuration.cs:line 60
at System.Data.Entity.Migrations.DbMigrationsConfiguration`1.OnSeed(DbContext context)
at System.Data.Entity.Migrations.DbMigrator.SeedDatabase()
at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.SeedDatabase()
at System.Data.Entity.Migrations.DbMigrator.Upgrade(IEnumerable`1 pendingMigrations, String targetMigrationId, String lastMigrationId)
at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.Upgrade(IEnumerable`1 pendingMigrations, String targetMigrationId, String lastMigrationId)
at System.Data.Entity.Migrations.DbMigrator.UpdateInternal(String targetMigration)
at System.Data.Entity.Migrations.DbMigrator.<>c__DisplayClassc.<Update>b__b()
at System.Data.Entity.Migrations.DbMigrator.EnsureDatabaseExists(Action mustSucceedToKeepDatabase)
at System.Data.Entity.Migrations.Infrastructure.MigratorBase.EnsureDatabaseExists(Action mustSucceedToKeepDatabase)
at System.Data.Entity.Migrations.DbMigrator.Update(String targetMigration)
at System.Data.Entity.Migrations.Infrastructure.MigratorBase.Update(String targetMigration)
at System.Data.Entity.Migrations.Design.ToolingFacade.UpdateRunner.Run()
at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
at System.Data.Entity.Migrations.Design.ToolingFacade.Run(BaseRunner runner)
at System.Data.Entity.Migrations.Design.ToolingFacade.Update(String targetMigration, Boolean force)
at System.Data.Entity.Migrations.UpdateDatabaseCommand.<>c__DisplayClass2.<.ctor>b__0()
at System.Data.Entity.Migrations.MigrationsDomainCommand.Execute(Action command)
Sequence contains no matching element
我一直在谷歌上搜索，似乎没有人有类似的问题。它就在这条线上var administrator = new List<Administrator>我输入了一个关于第 60 行在哪里的指针。
单击此处 SQL Server Management Studio 中的表
单击此处查看实体模型
public Configuration()
{
AutomaticMigrationsEnabled = false;
}
protected override void Seed(RecreationalServicesTicketingSystem.DAL.IssueContext context)
{
var departments = new List<Department>
{
new Department { DepartmentID = 1, Name = "IT"},
new Department { DepartmentID = 2, Name = "Admin" },
new Department { DepartmentID = 3, Name = "Human Resources"},
new Department { DepartmentID = 4, Name = "Mechanics" },
new Department { DepartmentID = 5, Name = "Directors" },
new Department { DepartmentID = 6, Name = "Operations"}
};
departments.ForEach(s => context.Departments.AddOrUpdate(p => p.Name, s));
context.SaveChanges();
var depots = new List<Depot>
{
new Depot { DepotID = 1, Name = "Porana"},
new Depot { DepotID = 2, Name = "Far North"},
};
departments.ForEach(s => context.Departments.AddOrUpdate(p => p.Name, s));
context.SaveChanges();
var users = new List<User>
{
new User { FirstMidName = "Jason", LastName = "Wan",
EnrollmentDate = DateTime.Parse("2016-02-18"), DepartmentID = 1, DepotID = 1},
new User { FirstMidName = "Andy", LastName = "Domagas",
EnrollmentDate = DateTime.Parse("2016-02-18"), DepartmentID = 1,DepotID = 1},
new User { FirstMidName = "Denis", LastName = "Djohar",
EnrollmentDate = DateTime.Parse("2016-02-18"), DepartmentID = 1 ,DepotID = 1},
new User { FirstMidName = "Christine", LastName = "West",
EnrollmentDate = DateTime.Parse("2016-02-18"), DepartmentID = 1, DepotID = 1},
};
var administrator = new List<Administrator> <-- LINE 60
{
new Administrator {AdminID = 1, AdminRole = "Administrator LVL1", User = users.Single ( s => s.UserID == 1),
Tickets = new List<Ticket>() },
new Administrator {AdminID = 2, AdminRole = "Administrator LVL2", User = users.Single ( s => s.UserID == 2),
Tickets = new List<Ticket>() },
new Administrator {AdminID = 3, AdminRole = "Administrator LVL3", User = users.Single ( s => s.UserID == 3),
Tickets = new List<Ticket>() }
};
administrator.ForEach(s => context.Administrators.AddOrUpdate(p => p.AdminID, s));
context.SaveChanges();
var categories = new List<Category>
{
new Category {CategoryID = 0001, Title = "Desktop"},
new Category {CategoryID = 0002, Title = "Mobile"},
new Category {CategoryID = 0003, Title = "Menzits"},
new Category {CategoryID = 0004, Title = "XMPRO"},
new Category {CategoryID = 0005, Title = "Con-X"},
new Category {CategoryID = 0006, Title = "Promapp"},
new Category {CategoryID = 0007, Title = "QGIS"},
};
categories.ForEach(s => context.Categories.AddOrUpdate(p => p.Title, s));
context.SaveChanges();
var tickets = new List<Ticket>
{
new Ticket {
UserID = users.Single(s => s.LastName == "Wan").UserID,
CategoryID = categories.Single(c => c.Title == "Con-X" ).CategoryID,
Issue = ("Test Error 1"),
Priority = Priority.High
},
new Ticket {
UserID = users.Single(s => s.LastName == "Wan").UserID,
CategoryID = categories.Single(c => c.Title == "Desktop" ).CategoryID,
Issue = ("Test Error 2"),
Priority = Priority.Med
},
};
foreach (Ticket e in tickets)
{
var ticketInDataBase = context.Tickets.Where(
s =>
s.User.UserID == e.UserID &&
s.Category.CategoryID == e.CategoryID).SingleOrDefault();
if (ticketInDataBase == null)
{
context.Tickets.Add(e);
}
}
context.SaveChanges();
}
}
用户.cs
public class User
{
public int UserID { get; set; }
[StringLength(50, MinimumLength = 1)]
public string LastName { get; set; }
[StringLength(50, MinimumLength = 1, ErrorMessage = "First name cannot be longer than 50 characters.")]
[Column("FirstName")]
public string FirstMidName { get; set; }
[DataType(DataType.Date)]
[DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
public DateTime EnrollmentDate { get; set; }
public string FullName
{
get { return LastName + ", " + FirstMidName; }
}
public int AdministratorID { get; set; }
[ForeignKey("AdministratorID")]
public virtual Administrator Administrator { get; set; }
public int DepartmentID { get; set; }
[ForeignKey("DepartmentID")]
public virtual Department Department { get; set; }
public int DepotID { get; set; }
[ForeignKey("DepotID")]
public virtual Depot Depot { get; set; }
public int TicketID { get; set; }
public virtual ICollection<Ticket> Users { get; set; }
}
部门.cs
public class Department
{
public int DepartmentID { get; set; }
[StringLength(50, MinimumLength = 1)]
public string Name { get; set; }
public virtual ICollection<User> Users { get; set; }
}
仓库.cs
public class Depot
{
public int DepotID { get; set; }
[StringLength(50, MinimumLength = 1)]
public string Name { get; set; }
public virtual ICollection<User> Users { get; set; }
}
当您创建用户时，您没有指定他们所属的部门，这意味着对于 int 字段，默认情况下它将为 0。数据库中没有 id 为 0 的部门，因此违反了外键约束。尝试类似操作：
var users = new List<User>
{
new User { FirstMidName = "Jason", LastName = "Wan",
EnrollmentDate = DateTime.Parse("2016-02-18"), DepartmentId = 1 },
new User { FirstMidName = "Andy", LastName = "Domagas",
EnrollmentDate = DateTime.Parse("2016-02-18"), DepartmentId = 1 },
new User { FirstMidName = "Denis", LastName = "Djohar",
EnrollmentDate = DateTime.Parse("2016-02-18"), DepartmentId = 1 },
new User { FirstMidName = "Christine", LastName = "West",
EnrollmentDate = DateTime.Parse("2016-02-18"), DepartmentId = 1 },
};
更新以解决仓库问题：
您正在创建站点，但是将它们添加到上下文中的行引用的是部门而不是站点：
var depots = new List<Depot>
{
new Depot { DepotID = 1, Name = "Porana"},
new Depot { DepotID = 2, Name = "Far North"},
};
departments.ForEach(s => context.Departments.AddOrUpdate(p => p.Name, s));// should be:
depots.ForEach(s => context.Depots.AddOrUpdate(p => p.Name, s));
context.SaveChanges();