连接字符串错误中缺少元数据

Question

我的第一个非常基本的与EF6相关的代码（选项“空代码优先模型”）引发异常（下面的标记行），声明connectionString中缺少元数据关键字。我应该设置什么CSDL，MDL，SSDL（元数据）作为模型为空？我想念什么？

//Model source file
public class Modelno : DbContext
{
    public Modelno(): base("name=Modelno") {}
    public virtual DbSet<MainTBL> MainTBLs { get; set; }
}

public class MainTBL
{
    public int GlId { get; set; }
    public string GlNam { get; set; }
}

//Form source file
private void button1_Click(object sender, EventArgs e)
{
    MainTBL gl = new MainTBL();
    gl.GlId = 1;
    gl.GlNam = "SomeName";

    Modelno modal = new Modelno();
    modal.MainTBLs.Add(gl); // exception here !
    modal.SaveChanges();
}

//App.config file (partially)
<connectionStrings>
   <add name="Modelno" connectionString="provider=FirebirdSql.Data.FirebirdClient;provider connection string=&quot;data source=localhost;initial catalog=D:\Fb\tab\TEST2.FDB;user id=SYSDBA;password=masterkey&quot;" providerName="System.Data.EntityClient"/>
</connectionStrings>