在https://docs.microsoft.com/en-us/aspnet/core/data/ef-mvc/sort-filter-page的MVC CORE演示中，Contoso大学示例程序在分页示例页面上使用模型
var students = from s in _context.Students
select s;
return View(await PaginatedList<Student>.CreateAsync(students.AsNoTracking(), page ?? 1, pageSize));
而viewmodel作为一个完整的实体传回来
var viewModel = new InstructorIndexData();
viewModel.Instructors = await _context.Instructors
.Include(i => i.OfficeAssignment)
.Include(i => i.CourseAssignments)
.ThenInclude(i => i.Course)
.ThenInclude(i => i.Department)
.OrderBy(i => i.LastName)
.ToListAsync();
return View(viewModel);
How do I paginate through the returned records of a viewmodel.
我已经尝试将viewmodel传递给像这样的PaginatedList .
return View(await PaginatedList<InstructorIndexData>.CreateAsync(viewModel.AsNoTracking(), page ?? 1, pageSize));
哪有错误
Error CS1061 'InstructorIndexData' does not contain a definition for 'AsNoTracking' and no extension method 'AsNoTracking' accepting a first argument of type 'InstructorIndexData' could be found (are you missing a using directive or an assembly reference?)
Edit ViewModel是
namespace ContosoUniversity.Models.SchoolViewModels
{
public class InstructorIndexData
{
public IEnumerable<Instructor> Instructors { get; set; }
public IEnumerable<Course> Courses { get; set; }
public IEnumerable<Enrollment> Enrollments { get; set; }
}
}
将IEnumerable更改为IQueryable会导致以下情况
var viewModel = new InstructorIndexData();
viewModel.Instructors = await _context.Instructors
.Include(i => i.OfficeAssignment)
.Include(i => i.CourseAssignments)
.ThenInclude(i => i.Course)
.ThenInclude(i => i.Department)
.OrderBy(i => i.LastName)
.ToListAsync();
产生错误
Cannot implicitly convert type 'System.Collections.Generic.List<ContosoUniversity.Models.Instructor>' to 'System.Linq.IQueryable<ContosoUniversity.Models.Instructor>'. An explicit conversion exists (are you missing a cast?)
1 回答
是在DbExtension程序集中定义的扩展方法 . 属性“Instructors”必须是实现“IQueryable”的类型才能启用此扩展方法 .
此外，在您提供的代码示例中
您正在使用viewModel本身的扩展方法而不是属性“Instructors”