查找对象列表中所有属性的最大值

Question

我有以下 Entity Framework Core 查询：

  IQueryable<Product> products = context.Products;

  var maximums = new MaximumModel {
    PA = await products.MaxAsync(x => x.Composition.PA)
    PB = await products.MaxAsync(x => x.Composition.PB)
    PC = await products.MaxAsync(x => x.Composition.PC)
    PD = await products.MaxAsync(x => x.Composition.PD)
    // Other 36 properties ...
  }

这会执行 40 个查询，每个查询一个 ...

有没有办法只执行一个查询？

Answer 1

我尚未使用 EF 异步版本对此进行测试，但 LINQ to SQL 解决方案是使用来自 GroupBy 的单例组将查询组合成一个查询：

var maximums = await products.GroupBy(p => 1)
                             .Select(pg => new MaximumModel {
                                                PA = pg.Max(x => x.Composition.PA),
                                                PB = pg.Max(x => x.Composition.PB),
                                                PC = pg.Max(x => x.Composition.PC),
                                                PD = pg.Max(x => x.Composition.PD),
                                                  // Other 36 properties ...
                             }).FirstAsync();