一起学ASP.NET Core 2.0学习笔记(二)- ef core2.0 及mysql provider 、Fluent API相关配置及迁移
2017-08-31 12:53
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不得不说微软的技术迭代还是很快的，上了微软的船就得跟着她走下去，前文一起学ASP.NET Core 2.0学习笔记(一): CentOS下 .net core2 sdk nginx、supervisor、mysql环境搭建搭建好了.net core linux的相关环境，今天就来说说ef core相关的配置及迁移:
简介:
Entity Framework(以下简称EF) 是微软以 ADO.NET 为基础所发展出来的对象关系对应 (O/R Mapping) 解决方案，EF Core是Entity framework得下一版本,相比EF原来版本(4-6.1)，显得更加轻量级,相比同样出身名门的dapper还是显得有点庞大,不过鱼与熊掌向来不可兼得,想想一堆堆语法糖,方便的linq查询以及lambda表达式,可以很大程度上从T-SQL语法上脱身出来很多,在配置过程中也碰到一些问题，记录下来,以便后期翻阅:
一.poco的创建以及Fluent Api关系配置
1.一对多关系:
项目中最常见的就是一对多关系了,以语言及语言为例
语言(Language)类
1 public partial class Language : BaseEntity<int>
2 {
3 private ICollection<LocaleStringResource> _localeStringResources;
4
5 /// <summary>
6 /// Gets or sets the name
7 /// </summary>
8
9 public string Name { get; set; }
10
11 /// <summary>
12 /// Gets or sets the language culture
13 /// </summary>
14
15 public string LanguageCulture { get; set; }
16
17 /// <summary>
18 /// Gets or sets the unique SEO code
19 /// </summary>
20
21 public string UniqueSeoCode { get; set; }
22
23 /// <summary>
24 /// Gets or sets the flag image file name
25 /// </summary>
26
27 public string FlagImageFileName { get; set; }
28
29 /// <summary>
30 /// Gets or sets a value indicating whether the language supports "Right-to-left"
31 /// </summary>
32
33 public bool Rtl { get; set; }
34
35
36 /// <summary>
37 /// Gets or sets a value indicating whether the language is published
38 /// </summary>
39
40 public<
11a94
/span> bool Published { get; set; }
41
42 /// <summary>
43 /// Gets or sets the display order
44 /// </summary>
45
46 public int DisplayOrder { get; set; }
47
48 public bool IsDefault { get; set; }
49
50 /// <summary>
51 /// Gets or sets locale string resources
52 /// </summary>
53 public virtual ICollection<LocaleStringResource> LocaleStringResources
54 {
55 get { return _localeStringResources ?? (_localeStringResources = new HashSet<LocaleStringResource>()); }
56 protected set { _localeStringResources = value; }
57 }View Code
语言资源(LocaleStringResource):
1 public partial class LocaleStringResource : BaseEntity<int>
2 {
3 /// <summary>
4 /// Gets or sets the language identifier
5 /// </summary>
6 public int LanguageId { get; set; }
7
8 /// <summary>
9 /// Gets or sets the resource name
10 /// </summary>
11 public string ResourceName { get; set; }
12
13 /// <summary>
14 /// Gets or sets the resource value
15 /// </summary>
16 public string ResourceValue { get; set; }
17
18 /// <summary>
19 /// Gets or sets a value indicating whether this resource was installed by a plugin
20 /// </summary>
21 public bool? IsFromPlugin { get; set; }
22
23 /// <summary>
24 /// Gets or sets a value indicating whether this resource was modified by the user
25 /// </summary>
26 public bool? IsTouched { get; set; }
27
28 /// <summary>
29 /// Gets or sets the language
30 /// </summary>
31 public virtual Language Language { get; set; }
32
33 }View Code
其中语言及资源主外键关系配置如下
1 public partial class LanguageMapper : IEntityTypeConfiguration<Language>
2 {
3 public void Configure(EntityTypeBuilder<Language> builder)
4 {
5 builder.ToTable("Language");
6 builder.HasKey(r => r.Id);
7 builder.HasIndex(r => r.LanguageCulture);
8 builder.HasIndex(r => r.Name);
9 builder.HasIndex(r => r.UniqueSeoCode);
10 }
11 }View Code
public partial class LocaleStringResourceMapper : IEntityTypeConfiguration<LocaleStringResource>
{
public void Configure(EntityTypeBuilder<LocaleStringResource> builder)
{
builder.ToTable("LocaleStringResource");
builder.HasKey(r => r.Id);
builder.HasIndex(r => r.LanguageId);
builder.HasIndex(r => r.ResourceName);
builder.HasOne(r => r.Language).WithMany(b => b.LocaleStringResources)
.HasForeignKey(fk => fk.LanguageId);
}
}2、父子关系 ：
1 public class TechCategory:BaseEntity<int>
2 {
3 /// <summary>
4 /// 名称
5 /// </summary>
6 public string Name { get; set; }
7 /// <summary>
8 /// 分类描述
9 /// </summary>
10 public string Descript { get; set; }
11 /// <summary>
12 /// meta标题
13 /// </summary>
14 public string MetaTitle { get; set; }
15 /// <summary>
16 /// meta描述
17 /// </summary>
18 public string MetaDescript { get; set; }
19 /// <summary>
20 /// 缩略图
21 /// </summary>
22 public string Thumb { get; set; }
23 /// <summary>
24 /// 图片
25 /// </summary>
26 public string Image { get; set; }
27 /// <summary>
28 /// 排序
29 /// </summary>
30 public int Sort { get; set; }
31 /// <summary>
32 /// 父级分类
33 /// </summary>
34 public int? ParentId { get; set; }
35
36 /// <summary>
37 /// 父级分类
38 /// </summary>
39
40 public virtual TechCategory Parent { get; set; }
41 public virtual ICollection<Technology> Technologys { get; set; }
42 /// <summary>
43 /// 子级
44 /// </summary>
45 public virtual ICollection<TechCategory> Childs { get; set; }
46 /// <summary>
47 /// 关键词
48 /// </summary>
49 public string Slug { get; set; }
50 /// <summary>
51 /// 创建时间
52 /// </summary>
53 public long CreatedOn { get; set; }
54 }View Code
1 public class TechCategoryMapper : IEntityTypeConfiguration<TechCategory>
2 {
3 public void Configure(EntityTypeBuilder<TechCategory> builder)
4 {
5 builder.ToTable("TechCategory");
6 builder.HasKey(r => r.Id);
7 builder.HasMany(r => r.Childs).WithOne(x => x.Parent)
8 .HasForeignKey(fk => fk.ParentId);
9 builder.HasIndex(r => r.Name);
10 }
11 }View Code
二、数据库上下文:
根据前面创建的相关实体类 以及相关mapper类型，我们可以重现DbContext的OnModelCreating的方法,反射出实现了IEntityTypeConfiguration接口的相关mapper类型创建相关实体-数据表的相关对应关系
1 public class DefaultContext : DbContext
2 {
3 public DefaultContext(DbContextOptions<DefaultContext> opt)
4 :base(opt)
5 {
6 AutoCommitEnabled = true;
7 }
8 protected override void OnModelCreating(ModelBuilder builder)
9 {
10 base.OnModelCreating(builder);
11 var mappingInterface = typeof(IEntityTypeConfiguration<>);
12 // Types that do entity mapping
13 var mappingTypes = GetType().GetTypeInfo().Assembly.GetTypes()
14 .Where(x => x.GetInterfaces().Any(y => y.GetTypeInfo().IsGenericType && y.GetGenericTypeDefinition() == mappingInterface));
15
16 // Get the generic Entity method of the ModelBuilder type
17 var entityMethod = typeof(ModelBuilder).GetMethods()
18 .Single(x => x.Name == "Entity" &&
19 x.IsGenericMethod &&
20 x.ReturnType.Name == "EntityTypeBuilder`1");
21
22 foreach (var mappingType in mappingTypes)
23 {
24
25 // Get the type of entity to be mapped
26 var genericTypeArg = mappingType.GetInterfaces().Single().GenericTypeArguments.Single();
27
28 // Get the method builder.Entity<TEntity>
29 var genericEntityMethod = entityMethod.MakeGenericMethod(genericTypeArg);
30
31 // Invoke builder.Entity<TEntity> to get a builder for the entity to be mapped
32 var entityBuilder = genericEntityMethod.Invoke(builder, null);
33
34 // Create the mapping type and do the mapping
35 var mapper = Activator.CreateInstance(mappingType);
36 mapper.GetType().GetMethod("Configure").Invoke(mapper, new[] { entityBuilder });
37 }
38 foreach (var relationship in builder.Model.GetEntityTypes().SelectMany(e => e.GetForeignKeys()))
39 {
40 relationship.DeleteBehavior = DeleteBehavior.Restrict;
41 }
42 }
43 }View Code
三、多数据库支持:
多数据库的支持，并不是意味着同时对多种数据库操作，当然，后面，我们会尝试同时对多种数据库操作，这可能需要多个上下文，暂且不论。分布式数据库。我们的项目可能是在windows上开发的使用的是SqlServer，我们要发布到linux上，SqlServer 2017 据说是支持liunx的，但是还没出... 当然不是说 SqlServer 就不能装在liunx上，但是我们的Liunx服务器可能已经安装了MySql或 Oracle，我们希望使用现有的，又或者是，我们需要切换数据库。那么，我们需要可以随时切换数据库的支持，以上篇的mysql为例：
1.引用相关包，mysql我用的Pomelo.EntityFrameworkCore.MySql，国人开发的mysql for ef core的相关服务对象,ef
core 2.0中需要指定2.0版本(Install-Package Pomelo.EntityFrameworkCore.MySql -Version 2.0.0-rtm-10059),
2.需改配置文件依据相关配置动态加载数据库提供对象；相关代码及配置如下
nuget引用列表
1 <ItemGroup> 2 <PackageReference Include="Microsoft.EntityFrameworkCore" Version="2.0.0" /> 3 <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="2.0.0" /> 4 <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="2.0.0" /> 5 <PackageReference Include="Pomelo.EntityFrameworkCore.MySql" Version="2.0.0-rtm-10058" /> 6 </ItemGroup>
View Code
相关配置文件修改
"ConnectionStrings": {
"MongoDbConnectionString": "mongodb://tchistory:tc123456@127.0.0.1/history",
"ConnectionString": "Data Source=127.0.0.1;Initial Catalog=farmdata;User ID=root;Password=123456",
"DataProvider": "MySql"
},在startup.cs 的configureServices方法中添加数据库上下文
public void ConfigureServices(IServiceCollection services)
{
services.AddDbContext<DefaultContext>(option => option.UseFarmDatabase(Configuration));
services.UseFarmService(Configuration);
services.AddMvc();
}数据库提供对象扩展方法如下:
public static DbContextOptionsBuilder UseFarmDatabase(this DbContextOptionsBuilder optionsBuilder, IConfiguration configuration)
{
string provider = configuration.GetConnectionString("DataProvider"), connection = configuration.GetConnectionString("ConnectionString");
if (provider.Equals(DataBaseServer.SqlServer, StringComparison.InvariantCultureIgnoreCase))
{
return optionsBuilder.UseSqlServer(connection);
}
else if (provider.Equals(DataBaseServer.MySql, StringComparison.InvariantCultureIgnoreCase))
{
return optionsBuilder.UseMySql(connection);
}
else
{
throw Error.Argument("UseDatabaseServer", "No databaseProvider");
}
}
在程序包管理控制台添加相关迁移 命令 add-migration init: 会在当前目录下生成相关迁移目录
执行update-database -Verbose提交更改到数据库,这样数据库迁移及更改就算完成了,其中要注意的地方是ef core 2.0 中有些数据库提供对象暂时是没有完全实现，如用Pomelo.EntityFrameworkCore.MySql -Version 1.1.2 可能会报方法未实现，更新2.0 rtm版本即可。
祝愿你在码农道路上越走越顺畅;
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