在代码优先实体框架中连接数据库时出错

Question

I am getting following error message when context is trying to connect to database using code-first approach of Entity Framework

System.Data.Entity.DbContext' does not contain a definition for 'System' and no extension method 'System' accepting a first argument of type 'System.Data.Entity.DbContext' could be found (are you missing a using directive or an assembly reference?)

Code:

public class Context : DbContext, IDisposable
{
    public Context() : base("EcommConnectionString")
    {
    }

    public List<Entities.RLI_State> States { get; set; }
    public List<Entities.RLI_Product> Products { get; set; }
    public List<Entities.RLI_StateProduct_List> StateProductList { get; set; }
}

This is how my connection string defined in web.config :

<appSettings>
    <add key="EcommConnectionString" 
         value="data source=localhost;initial catalog=tempdb;integrated security=SSPI" />
</appSettings>

Answer 1

There are a couple of problems here.

Firstly, DbContext already imlpements IDisposable so you don't need that. It's not a problem having it there, but it is redundant.

Secondly your List<> properties should be using DbSet<> instead:

public class Context : DbContext
{
    public Context() : base("EcommConnectionString")
    {
    }

    public DbSet<Entities.RLI_State> States { get; set; }
    public DbSet<Entities.RLI_Product> Products { get; set; }
    public DbSet<Entities.RLI_StateProduct_List> StateProductList { get; set; }
}

Finally, as @marc_s mentioned, the connection string in your web.config should be in the <connectionStrings> element, not in <appSettings> :

<connectionStrings>
    <add name="EcommConnectionString" 
         connectionString="data source=localhost;initial catalog=tempdb;integrated security=SSPI" />
</connectionStrings>