之后,立即加载“类型之间未定义强制运算符”。NET Core/EF Core 2.0升级

在里面NET Core 1。x、 我们有这样一种方法:

public async Task<(PaperRecord Component, PaperPointerRecord Pointer)> GetOneAsync(DbSet<PaperPointerRecord> paperPointerRecords,
                                                                                   int? paperId = null,
                                                                                   long? externalPaperId = null,
                                                                                   Expression<Func<PaperPointerRecord, bool>> filter = null)
{
    var query = filter is null ? paperPointerRecords.AsQueryable() : paperPointerRecords.Where(filter);

    if (paperId.HasValue)
        query = query.Where(_ => _.PaperPointerId == paperId);

    if (externalPaperId.HasValue)
        query = query.Where(_ => _.ExternalId == externalPaperId);

    var record = await query.Include(_ => _.Paper)
                            .ThenInclude(_ => _.PaperColors)
                            .Select(_ => new
                                         {
                                             PaperRecord = _.Paper,
                                             PaperPointerRecord = _
                                         })
                            .SingleOrDefaultAsync();

    return !(record is null) ? (record.PaperRecord, record.PaperPointerRecord) : throw NewPaperRecordNotFoundException(paperId, externalPaperId);
}

这对我们来说非常有效。在将整个项目升级到所有内容之后。NET Core 2.0和;EF Core 2.0中,该方法引发此异常:

系统发生InvalidOperationException:在类型“PaperPointerRecord”和“PaperRecord”之间未定义强制运算符。

var record = await query.Include(_ => _.Paper)
                        .ThenInclude(_ => _.PaperColors)
                        .Select(_ => new
                                     {
                                         PaperRecord = _.Paper,
                                         PaperPointerRecord = _
                                     })
                        .SingleOrDefaultAsync();

如果我删除了即时加载并这样做,那么错误就会消失,但我也没有得到预期的结果:

var record = await query.Select(_ => new
                                     {
                                         PaperRecord = _.Paper,
                                         PaperPointerRecord = _
                                     })
                        .SingleOrDefaultAsync();

我已经查过了 Microsoft Documentation