C# EF Core无法将数据从旧的SQL Server数据库传输到新的SQL Server数据库

复制步骤

我有一个ASP.NETCore2.2Web应用程序，其后端SQLServerDB是在本教程的EntityFrameworkCore中创建的

总结这些步骤

在链接中下载项目

转到

appsettings.json

将连接字符串中的数据库名称更改为

contosuniversity2

保存更改并生成项目

确保没有程序实例正在运行，并使用CLI（命令行界面）或PMC（包管理控制台），导航到项目文件夹并输入此命令

dotnet ef迁移添加InitialCreate

现在输入命令

dotnet ef数据库更新

预期行为

实体框架将数据从以前名为ContosoUniversity1的数据库迁移到ContosoUniversity2，包括所有列和表。它在Visual Studio 2019中为作者工作

实际行为

我只看到所有表和列的创建。除了在迁移历史记录中只有一行的_EFMigrationsHistory中，没有其他数据。我从CLI获取此输出

`Build started...
Build succeeded.
info: Microsoft.EntityFrameworkCore.Infrastructure[10403]
      Entity Framework Core 2.2.6-servicing-10079 initialized 'SchoolContext' us
ing provider 'Microsoft.EntityFrameworkCore.SqlServer' with options: None
info: Microsoft.EntityFrameworkCore.Database.Command[20101]
      Executed DbCommand (666ms) [Parameters=[], CommandType='Text', CommandTime
out='60']
      CREATE DATABASE [ContosoUniversity2];
info: Microsoft.EntityFrameworkCore.Database.Command[20101]
      Executed DbCommand (161ms) [Parameters=[], CommandType='Text', CommandTime
out='60']
      IF SERVERPROPERTY('EngineEdition') <> 5
      BEGIN
          ALTER DATABASE [ContosoUniversity2] SET READ_COMMITTED_SNAPSHOT ON;
      END;
info: Microsoft.EntityFrameworkCore.Database.Command[20101]
      Executed DbCommand (18ms) [Parameters=[], CommandType='Text', CommandTimeo
ut='30']
      CREATE TABLE [__EFMigrationsHistory] (
          [MigrationId] nvarchar(150) NOT NULL,
          [ProductVersion] nvarchar(32) NOT NULL,
          CONSTRAINT [PK___EFMigrationsHistory] PRIMARY KEY ([MigrationId])
      );
info: Microsoft.EntityFrameworkCore.Database.Command[20101]
      Executed DbCommand (3ms) [Parameters=[], CommandType='Text', CommandTimeou
t='30']
      SELECT OBJECT_ID(N'[__EFMigrationsHistory]');
info: Microsoft.EntityFrameworkCore.Database.Command[20101]
      Executed DbCommand (1ms) [Parameters=[], CommandType='Text', CommandTimeou
t='30']
      SELECT [MigrationId], [ProductVersion]
      FROM [__EFMigrationsHistory]
      ORDER BY [MigrationId];
info: Microsoft.EntityFrameworkCore.Migrations[20402]
      Applying migration '20191227004521_InitialCreate'.
Applying migration '20191227004521_InitialCreate'.
info: Microsoft.EntityFrameworkCore.Database.Command[20101]
      Executed DbCommand (2ms) [Parameters=[], CommandType='Text', CommandTimeou
t='30']
      CREATE TABLE [Course] (
          [CourseID] int NOT NULL,
          [Title] nvarchar(max) NULL,
          [Credits] int NOT NULL,
          CONSTRAINT [PK_Course] PRIMARY KEY ([CourseID])
      );
info: Microsoft.EntityFrameworkCore.Database.Command[20101]
      Executed DbCommand (2ms) [Parameters=[], CommandType='Text', CommandTimeou
t='30']
      CREATE TABLE [Student] (
          [ID] int NOT NULL IDENTITY,
          [LastName] nvarchar(max) NULL,
          [FirstMidName] nvarchar(max) NULL,
          [EnrollmentDate] datetime2 NOT NULL,
          CONSTRAINT [PK_Student] PRIMARY KEY ([ID])
      );
info: Microsoft.EntityFrameworkCore.Database.Command[20101]
      Executed DbCommand (3ms) [Parameters=[], CommandType='Text', CommandTimeou
t='30']
      CREATE TABLE [Enrollment] (
          [EnrollmentID] int NOT NULL IDENTITY,
          [CourseID] int NOT NULL,
          [StudentID] int NOT NULL,
          [Grade] int NULL,
          CONSTRAINT [PK_Enrollment] PRIMARY KEY ([EnrollmentID]),
          CONSTRAINT [FK_Enrollment_Course_CourseID] FOREIGN KEY ([CourseID]) RE
FERENCES [Course] ([CourseID]) ON DELETE CASCADE,
          CONSTRAINT [FK_Enrollment_Student_StudentID] FOREIGN KEY ([StudentID])
 REFERENCES [Student] ([ID]) ON DELETE CASCADE
      );
info: Microsoft.EntityFrameworkCore.Database.Command[20101]
      Executed DbCommand (1ms) [Parameters=[], CommandType='Text', CommandTimeou
t='30']
      CREATE INDEX [IX_Enrollment_CourseID] ON [Enrollment] ([CourseID]);
info: Microsoft.EntityFrameworkCore.Database.Command[20101]
      Executed DbCommand (1ms) [Parameters=[], CommandType='Text', CommandTimeou
t='30']
      CREATE INDEX [IX_Enrollment_StudentID] ON [Enrollment] ([StudentID]);
info: Microsoft.EntityFrameworkCore.Database.Command[20101]
      Executed DbCommand (2ms) [Parameters=[], CommandType='Text', CommandTimeou
t='30']
      INSERT INTO [__EFMigrationsHistory] ([MigrationId], [ProductVersion])
      VALUES (N'20191227004521_InitialCreate', N'2.2.6-servicing-10079');
Done.`

---

迁移没有什么问题。解决方案是恢复到备份文件夹中的上一个备份，复制并粘贴教程中的代码，而不是手工编写。事实证明，我只拼错了一行，并且能够纠正错误。

您是否希望所有表中的数据都被复制到另一个表中？是@BrendanGreen，因为在MS教程的图像中显示数据被复制到另一个表中。我想你误读了这里的一个词。迁移用于将同一数据库中的数据从一个版本（表结构）迁移到另一个版本。@vasily sib，所以它应该像我想的那样跨数据库复制数据。但是我已经读了一遍又一遍的步骤。我想知道我可能错过了什么。@JordanNash“迁移”不复制数据。它们只是对数据库模式进行更改。在这种情况下，您已经有效地设置了一个新的连接字符串。我假设“新”数据库还不存在，所以迁移应用了创建新数据库的命令，并创建模式（表、索引、视图等），以便与应用程序中EF上下文中配置的内容相匹配。如果数据库中已经存在数据，则如果可能，这些命令将保留这些数据。

.NET Core SDK (reflecting any global.json):
 Version:   2.2

Runtime Environment:
 OS Name:     Windows
 OS Version:  6.1.7601
 OS Platform: Windows
 RID:         win7-x64