SQLite.Net - 不知道 System.Collections.Generic.List 错误 - Xamarin Android

Question

我在这个问题上搜索了几个小时，他不知道能力是非常合乎逻辑的（因为能力还没有制作出来），但是你们知道如何解决这个问题吗？

这是我收到的错误消息： 不知道 System.Collections.Generic.List`1[pokedex.Ability]

我的课程： -能力

[Table ("Ability")]
public class Ability
{
    [PrimaryKey,AutoIncrement]
    public int Id { get; set; }

    public String name{ get; set; }

    [ManyToMany (typeof(PokemonAbility))]
    public List<Pokemon> pokemon{ get; set; }

    public Ability (String n)
    {
        name = n;
    }
}

-口袋妖怪：

[Table ("Pokemon")]
public class Pokemon
{
    [PrimaryKey,AutoIncrement]
    public int DBId { get; set; }

    public int id { get; set; }

    public String name{ get; set; }

    public String type{ get; set; }

    public String image{ get; set; }

    public int Attack{ get; set; }

    public int speed{ get; set; }

    public int sp_atk{ get; set; }

    public int sp_def{ get; set; }

    public int defense{ get; set; }

    public string height{ get; set; }

    public String weight{ get; set; }

    public int hp{ get; set; }

    public String description{ get; set; }

    [ManyToMany (typeof(PokemonAbility))]
    public List<Ability> abilities{ get; set; }

    methods and consttuctor...


}

口袋妖怪能力：

[Table ("PokemonAbility")]
public class PokemonAbility
{
    public PokemonAbility ()
    {
    }

    [ForeignKey (typeof(Pokemon))]
    public int PokemonId { get; set; }

    [ForeignKey (typeof(Ability))]
    public int AbilityId { get; set; }
}

我的数据库：

public class NormalDatabase
{

    private String pathToDatabase;

    public NormalDatabase ()
    {
        var documents = Environment.GetFolderPath (Environment.SpecialFolder.Personal);
        pathToDatabase = Path.Combine (documents, "db_adonet.db");
    }

    //aanmaken van de tabel => met objecten pokemon
    public void CreateDatabase ()
    {
        using (var conn = new SQLite.SQLiteConnection (pathToDatabase)) {
            conn.DropTable<Pokemon> ();
            conn.DropTable<Ability> ();
            conn.DropTable<PokemonAbility> ();
            conn.CreateTable<Pokemon> ();  //here he fails ofc
            conn.CreateTable<Ability> ();
            conn.CreateTable<PokemonAbility> ();
        }
    other methods
    }

提前致谢！

Answer 1

列表不是 SQLite 数据库值的有效类型。

查看以下有效类型：

    public static string SqlType (TableMapping.Column p, bool storeDateTimeAsTicks)
    {
        var clrType = p.ColumnType;
        if (clrType == typeof(Boolean) || clrType == typeof(Byte) || clrType == typeof(UInt16) || clrType == typeof(SByte) || clrType == typeof(Int16) || clrType == typeof(Int32)) {
            return "integer";
        } else if (clrType == typeof(UInt32) || clrType == typeof(Int64)) {
            return "bigint";
        } else if (clrType == typeof(Single) || clrType == typeof(Double) || clrType == typeof(Decimal)) {
            return "float";
        } else if (clrType == typeof(String)) {
            int len = p.MaxStringLength;
            return "varchar(" + len + ")";
        } else if (clrType == typeof(DateTime)) {
            return storeDateTimeAsTicks ? "bigint" : "datetime";
            #if !NETFX_CORE
        } else if (clrType.IsEnum) {
            #else
        } else if (clrType.GetTypeInfo().IsEnum) {
            #endif
            return "integer";
        } else if (clrType == typeof(byte[])) {
            return "blob";
        } else if (clrType == typeof(Guid)) {
            return "varchar(36)";
        } else {
            throw new NotSupportedException ("Don't know about " + clrType); //Here the exception is thrown
        }
    }

Answer 2

我认为这是因为您的能力表定义中的拼写错误。在 ManyToMany 属性中，您应该使用“Pokemon”而不是“Pokmemons”。此外，您的另一个表是“能力”而不是“能力”。如果没有帮助，请更新帖子...

Answer 3

请参考异常类型：NotSupportedException。

请看这里：how to create collection (1:n) relation