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在EF中使用MySQL的方法及常见问题

时间:2021-07-01 10:21:17 帮助过:1人阅读

    完整的web.config如下:

     
<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
  </configSections>
  <entityFramework>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory , EntityFramework" />
    <providers>
      <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
      <provider invariantName="MySql.Data.MySqlClient" type="MySql.Data.MySqlClient.MySqlProviderServices, MySql.Data.Entity.EF6, Version=6.9.8.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d">
      </provider>
    </providers>
  </entityFramework>
  <system.data>
    <DbProviderFactories>
      <remove invariant="MySql.Data.MySqlClient" />
      <add name="MySQL Data Provider" invariant="MySql.Data.MySqlClient" description=".Net Framework Data Provider for MySQL" type="MySql.Data.MySqlClient.MySqlClientFactory, MySql.Data, Version=6.9.8.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d" />
    </DbProviderFactories>
  </system.data>
  <connectionStrings>
    <add name="MyContext" connectionString="Data Source=localhost;port=3306;Initial Catalog=MySQL_EF;user id=root;password=root;" providerName="MySql.Data.MySqlClient" />
  </connectionStrings>
</configuration> 

 

  最后,运行程序,完成数据库自动创建  

常见问题

  • 出现错误提示: Specified key was too long;max key length is 767 bytes
        1)查看实体的字符串类型属性是否设置了长度         2)MyContext 类中是否声明为生成为mysql 数据类型的 [DbConfigurationType(typeof(MySqlEFConfiguration))]
  • 出现错误提示:    Model compatibility cannot be checked because the database does not contain model metadata
        删除已生成的数据库后重新运行程序
  • 出现错误提示:序列不包含任何匹配元素
        检查一下:
例如:1.
public class Employee
{
  [Key]
  public int EmployeeId { get; set; }
  public string Name { get; set; }

  [ForeignKey("ManagerId")]
  public Employee Manager { get; set; }
  public int ManagerId { get; set; }
}

[ForeignKey("ManagerId")]
public Employee Manager { get; set; }
public int ManagerId { get; set; }
这个外键设置。

 


2.

[Column(TypeName="VARCHAR(254)")]
public string ColumnName { get; set; }
这样的定义,改成:
[MaxLength(254)] [Column(TypeName="VARCHAR")]
public string ColumnName { get; set; }

3.(以下代码未测试,因为我不是这样用的,在下篇文章中将进行测试)
modelBuilder.Entity<Category>()
               .HasKey(c => c.IdCategory )
               .HasOptional(p => p.Children)
               .WithMany()
               .HasForeignKey(c => c.ChildrenId);
改成:
modelBuilder.Entity<Category>()
               .HasKey(c => c.IdCategory )
               .HasMany(p => p.Children)
               .WithOptional()
               .HasForeignKey(c => c.ChildrenId);

.WithMany()换成.WithOptional()

在EF中使用MySQL的方法及常见问题

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