Question

我怎么能这样做？我认为问题在于“选择”中的连接。

var respaldos = db.Respaldoes.Where(x => x.type == "Backup")
    .Where(x => x.start_time >= _desde && x.start_time <= _hasta)
    .GroupBy(x => new
    {
        x.start_time.Year,
        x.start_time.Month,
        x.start_time.Day
    })
    .Select(x => new
    {
        periodo = x.Key.Day + "/" + x.Key.Month + "/" + x.Key.Year,
        objetos = x.Sum(y => y.bytes_processed)
    });

foreach (var obj in respaldos)
{
    Dictionary<string, string> dicciconario = new Dictionary<string, string>();
    dicciconario.Add("periodo", obj.periodo.ToString());
    dicciconario.Add("objetos", obj.objetos.ToString());
}

运行应用时出错，错误发生在“foreach”

错误： No se pudo convertir el tipo'System.Int32'al tipo'System.Object'。 LINQ to Entitiessóloinlaladisteiónadtiposdeenumeraciónoprimitivos de EDM。

我尝试白衣：

.Select(x => new
{
    periodo = x.Key.Day.ToString() + "/" + x.Key.Month.ToString() + "/" + x.Key.Year.ToString(),
    objetos = x.Sum(y => y.bytes_processed)
});

我收到其他错误：

LINQ to Entities no reconoceelmétodoSystem.StringToString（）delmétodo，yestemétodonose puede traducir enunaexpresióndealmacén。

Answer 1

看起来您希望按照没有时间组件的日期进行分组。 EF具有以下功能：DbFunctions.TruncateTime：

var respaldos = db.Respaldoes.Where(x => x.type == "Backup")
    .Where(x => x.start_time >= _desde && x.start_time <= _hasta)
    .GroupBy(x => DbFunctions.TruncateTime(x.start_time))
    .Select(x => new
    {
        periodo = x.Key, // Now a DateTime value
        objetos = x.Sum(y => y.bytes_processed)
    });

在此之后，您可以

Dictionary<DateTime, int> dicciconario =
   respaldos.ToDictionary(x => x.periodo, x => x.objetos);

实体框架查询选择新的concat

1 个答案: