我编写了一个 C# MVC5 Internet 应用程序，并且对使用 .ToListAsync LINQ 表达式有疑问。
这是我在索引操作结果中运行的代码:
IEnumerable<IMapLocationItem> mapLocationImageGalleries = await db.mapLocationImageGalleries.Where(m => m.userName.Equals(userName)).ToListAsync();
IEnumerable<IMapLocationItem> mapLocationVideoGalleries = await db.mapLocationVideoGalleries.Where(m => m.userName.Equals(userName)).ToListAsync();
IEnumerable<IMapLocationItem> mapLocationItemsCombined = mapLocationImageGalleries.Concat(mapLocationVideoGalleries);
我想为上面的代码创建一个服务函数。这是我编写的代码:
public async Task<IEnumerable<IMapLocationItem>> GetAllMapLocationItemsFromUserName(string userName)
{
IEnumerable<IMapLocationItem> mapLocationImageGalleries = await db.mapLocationImageGalleries.Where(m => m.userName.Equals(userName)).ToListAsync();
IEnumerable<IMapLocationItem> mapLocationVideoGalleries = await db.mapLocationVideoGalleries.Where(m => m.userName.Equals(userName)).ToListAsync();
IEnumerable<IMapLocationItem> mapLocationItemsCombined = mapLocationImageGalleries.Concat(mapLocationVideoGalleries);
return mapLocationItemsCombined;
}
我收到以下错误:
Error 17 'System.Linq.IQueryable<CanFindLocation.Models.MapLocationItems.MapLocationImageGallery>' does not contain a definition for 'ToListAsync' and no extension method 'ToListAsync' accepting a first argument of type 'System.Linq.IQueryable<CanFindLocation.Models.MapLocationItems.MapLocationImageGallery>' could be found (are you missing a using directive or an assembly reference?)
完全相同的代码在 Index 操作结果中工作正常，但在服务方法中却不行。为什么会这样，我怎样才能让它发挥作用？
提前致谢
最佳答案
如评论中所述，添加 using System.Data.Entity(在 Entity Framework 包下)以获取 QueryableExtensions。
对于 .NET Core，这些方法在 Microsoft.EntityFrameworkCore 下
关于c# - 带有 DbSet 的 LINQ ToListAsync 表达式，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/25174004/