SQLite System.NotSupportedException：不知道如何读取<t>

Question

我使用Xamarin Forms和Sqlite开发应用程序。 我使用以下小块：

1. sqlite-net-pcl
2. SQLiteNetExtensions

我想用sql创建查询。

我有两个表：

CREATE TABLE `AuditFormDto` (
    `AuditDtoGuid`  varchar,
    `Id`    integer NOT NULL PRIMARY KEY AUTOINCREMENT,
    `Guid`  varchar,
    `AuditFormTradePointDtoId`  integer,
    `CreationLocationJson`  varchar,
    `CompletionLocationJson`    varchar,
    `CreationDate`  bigint,
    `CompletionDate`    bigint,
    `Status`    integer,
    `PlaceInAudit`  integer,
    `CreatorId` varchar,
    `ServerId`  integer,
    `AuditServerId` integer,
    `ShouldSync`    integer,
    `Deleted`   integer
);

和

CREATE TABLE `AuditDto` (
    `CreatorId` varchar,
    `RegularQuestionIdsBlobbed` varchar,
    `CreationLocationJson`  varchar,
    `CompletionLocationJson`    varchar,
    `Guid`  varchar NOT NULL,
    `DateCreated`   bigint,
    `DateFinished`  bigint,
    `Name`  varchar,
    `Comment`   varchar,
    `Type`  integer,
    `Status`    integer,
    `ServerId`  integer,
    `ShouldSync`    integer,
    PRIMARY KEY(`Guid`)
);

我还创建了包装器类

public class JoinedClass 
{
    public string AuditDtoGuid { get; set; }
    public int Id { get; set; }
    public int Type { get; set; }
    public string Guid { get; set; }
}

但是当我尝试执行此代码时：

public async Task<JoinedClass> Get(int id)
{
    var strQuery = $"SELECT * FROM AuditFormDto INNER JOIN AuditDto ON  AuditDto.Guid = AuditFormDto.AuditDtoGuid where AuditFormDto.Id = {id}";
    var joinedClass = await _connection.ExecuteScalarAsync<JoinedClass>(strQuery);
    return joinedClass;
}

我有这个例外：

System.NotSupportedException: Don't know how to read JoinedClass

Answer 1

ExecuteScalarAsync返回有效计数而不是行结果。

您可以使用QueryAsync进行更改。

它看起来像：

public async Task<IEnumerable<JoinedClass>> Get(int id)
{
    var strQuery = $"SELECT * FROM AuditFormDto INNER JOIN AuditDto ON  AuditDto.Guid = AuditFormDto.AuditDtoGuid where AuditFormDto.Id = {id}";
    var joinedClass = await _connection.QueryAsync<JoinedClass>(strQuery);
    return joinedClass;
}