Xamarin.Forms在ManyToOne关系上的Sqlite-net NotSupportedException“不知道< model>" [英] Xamarin.Forms Sqlite-net NotSupportedException on ManyToOne relationship "Don't know about <model>"

问题描述

我在xamarin.forms应用程序中使用sqlite net扩展库.我在PCL中编写数据库代码和模型.

I am using sqlite net extensions library in my xamarin.forms application. I code in my PCL the database code and models.

当我调用SQLiteConnection.CreateTable()时出现错误 System.NotSupportedException: Don't know about Cigars.Models.Cigar

When I call SQLiteConnection.CreateTable() I get an error System.NotSupportedException: Don't know about Cigars.Models.Cigar

烟是雪茄的孩子，它具有ManyToOne关系. 这是模型:

Smoke is a child of Cigar, it has a ManyToOne relationship. Here are the models:

抽烟

public class Smoke
{

    [PrimaryKey]
    public int SmokeId { get; set; }

    [ForeignKey(typeof(Cigar))]
    public int CigarId { get; set; }

    public string Notes { get; set; }

    public DateTime DateCreated { get; set; }

    //why is this not recognized?
    [ManyToOne]
    public Cigar Cigar { get; set; }

}

雪茄

public class Cigar
{

    [PrimaryKey]
    public int CigarId { get; set; }

    public string Name { get; set; }

    public double Length { get; set; }
}

我的引发异常的数据库调用:

My database call that causes the exception to be thrown:

private SQLiteConnection db;

public Database(string path)
{
    db = new SQLiteConnection(path);
    db.CreateTable<Cigar>();
    db.CreateTable<Smoke>(); //this throws the error
}

推荐答案

问题是我为sqlite安装了两个不同的库，都包含SQLiteConnection.

The problem was that I had installed two different libraries for sqlite, both containing a SQLiteConnection.

我需要将Sqlite.Net.SQLiteConnection类用于sqlite网络扩展.不是我正在使用的Sqlite.SQLiteConnection.

I needed to use the Sqlite.Net.SQLiteConnection class for sqlite net extensions. Not the Sqlite.SQLiteConnection I was using.

如SushiHangover所指出的，此Sqlite.Net.SQLiteConnection接受类型为ISQLitePlatform的第一个参数.

As SushiHangover pointed out, this Sqlite.Net.SQLiteConnection takes a first argument of type ISQLitePlatform.

为此，我定义了一个接口，该接口提供了返回ISQLitePlatform的方法的签名:

To obtain a reference for this, I defined an interface that provides the signature of a method to return a ISQLitePlatform:

public interface ISQLitePlatformInstance
{
    ISQLitePlatform GetSQLitePlatformInstance();
}

然后在我的Droid项目(我要建立的平台)中实现了该接口:

And I implemented the interface in my Droid project ( the platform I'm building against):

public class SQLitePlatformInstance : ISQLitePlatformInstance
{

    public ISQLitePlatform GetSQLitePlatformInstance()
    {
        return new SQLitePlatformAndroid();
    }

}

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