Ways to use MySQL in EF and frequently asked questions

Sometimes you need to rent a space or database online, MySQL cost is lower, so you want to turn SQL Server into MySQL ...

Note: When you install MySQL, select the text set as UTF8, otherwise you will not be able to use Chinese (you can also use UTF8 when you create the database, but I do not know how to set it when EF builds the database, I hope the expert pointing)

One, the EF package that references MySQL in the project

Install via NuGet Package Manager: EntityFramework6.1.3, mysql.data.entity6.9.8 can also be added with NuGet's command line:

Install-Package MySql.Data.Entity

Second, the new related classes 1. New User entity classand define the field length of the instance, undefined words will appear specified key was too Long;max key length is 767 bytes error, this is because the string type directly mapped to MySQL is Longtext, and MySQL  Supports a maximum length of 767 bytes.         public class User {public int Id {get; set;}        [Stringlength] public string UserName {get; set;}      [MaxLength] public string PassWord {get; set;} } 2. New Mycontext classand instructions are implemented with MySQL [Dbconfigurationtype (typeof (Mysqlefconfiguration))]
     [Dbconfigurationtype (typeof (Mysqlefconfiguration))]    public class  MyContext : DbContext    {         Public mycontext ()             : base (" Name=mycontext ")//web.config connectionstring name         {         }         public dbset <user> users { get; set; }    }  3, write test code             database.setinitializer (new dropcreatedatabaseifmodelchanges< Mycontext> ());             var  Context = new mycontext ();             //inserting a row of values             context. Users.add (new user { username =  "Ef6mysql" &NBSP;});             context. SaveChanges ();   Three, configure web.config    Add the following code to <connectionStrings>:   <add name= "mycontext" connectionstring= "Data source=localhost;port=3306;initial catalog=mysql_ef;user id= root;password=root; "Providername=" MySql.Data.MySqlClient "/>

The complete Web. config is as follows:

 

<?XML version= "1.0" encoding= "Utf-8"?><Configuration>  <configsections>    <!--for more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -    < Sectionname= "EntityFramework"type= "System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, version=6.0.0.0, culture= Neutral, publickeytoken=b77a5c561934e089 "requirepermission= "false" />  </configsections>  <EntityFramework>    <defaultconnectionfactorytype= "System.Data.Entity.Infrastructure.SqlConnectionFactory, entityframework" />    <providers>      <providerInvariantName= "System.Data.SqlClient"type= "System.Data.Entity.SqlServer.SqlProviderServices, entityframework.sqlserver" />      <providerInvariantName= "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>      <Removeinvariant= "MySql.Data.MySqlClient" />      <Addname= "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>    <Addname= "Mycontext"connectionString= "Data source=localhost;port=3306;initial catalog=mysql_ef;user id=root;password=root;"ProviderName= "MySql.Data.MySqlClient" />  </connectionStrings></Configuration> 

 Finally, run the program to complete the database auto-creation FAQ

• Error message: Specified Key was too Long;max key length is 767 bytes

1) See if the String Type property of the entity is set to length 2) whether the Mycontext class declares a living as a MySQL data type [Dbconfigurationtype (typeof (Mysqlefconfiguration))]

• Error message: Model Compatibility cannot is checked because the database does not contain model metadata

Rerun a program after you delete a database that has been built

• Error message: Sequence does not contain any matching elements

  Check:

For example: 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;}}



public int ManagerID {get; set;}
This foreign key setting.

2.

[Column (Typename= "VARCHAR (254)")]



public string ColumnName {get; set;}

3.(The following code is not tested because I am not using it, and will be tested in the next article)

Modelbuilder.entity<category> ()               . Haskey (c = c.idcategory)               . Hasoptional (p = p.children)               . Withmany ()               . Hasforeignkey (c = c.childrenid); change to:modelbuilder.entity<category> ()               . Haskey (c = c.idcategory)               . Hasmany (p = p.children)               . Withoptional ()               . Hasforeignkey (c = C.childrenid);. Withmany () replaced. Withoptional ()

Ways to use MySQL in EF and frequently asked questions