How do I use async Task<IActionResult> ? Or How to run in async way in my Asp.Net Core Web Api

Question

I'am trying to run my Controller Action in async way. How do I use async Task ? Or How to run in async way

// Db context
public class DeptContext : DbContext
{
    public LagerContext(DbContextOptions<LagerContext> options)
        : base(options)
    {

        Database.Migrate();
    }

    public DbSet<Department> Departments { get; set; }
    public DbSet<Product> Products { get; set; }


}

// This is my Interface IDepRepository

Task<Department> GetDepartmentWithOrWithoutProducts(int deptId, bool includeProducts);

// And my Repository class DepRepository

public class DepRepository : IDepRepository
{
   private DeptContext db;
    public DepRepository(DeptContext context)
    {
        db = context;
    }

    // I'am geting Department name with products or Without products

    public async Task<Department> GetDepartmentWithOrWithoutProducts(int deptId, bool includeProducts)
     {
       if(includeProductss)
        {
          return await db.Departments.Include(c => c.Products).Where(s => s.deptId == deptId).SingleAsync();
        }
                return await db.Departments.Where(s => s.deptId == deptId).SingleAsync();
    }
}

So How should I do now in my Controller to do it as async way: I tried as following but I don't know if it's right to do like this following: I'm not getting any error but I don't if it's right way ...

using System.Threading.Tasks;
using System.Net;
using Microsoft.Data.Entity;
using Microsoft.EntityFrameworkCore;

[Route("api/departments")]
public class DepartmentsController : Controller
{
    private IDeptRepository _deptInfoRepository;

    public DepartmentsController(IDeptRepository deptInfoRepository)
    {
        _deptInfoRepository = deptInfoRepository;
    }

    [HttpGet("{id}")]
    public async Task<IActionResult> GetDepatment(int id, bool includeProducts = false)
    {
        var dept = _deptInfoRepository.GetDepartmentWithOrWithoutProducts(id, includeComputers);
        if(dept == null)
        {
            return BadRequest();
        }

        if(includeProducts)
        {
            var depResult =  new DepartmentDto() { deptId = dept.deptId, deptName = dept.deptName };
            foreach(var department in dept.Products)
            {
                depResult.Products.Add(new ProductDto() { productId = department.productId, deptId = department.deptId, ProductName =                     department.ProductName });
            } 

            return Ok(depResult);
        }

        var departmentWithoutProductResult = new DepartmentsWithoutProductsDto() { DeptId = dept.deptId, DeptName = dept.DeptName};
        return Ok(departmentWithoutProductResult);


    }

How do I do to get my controller in async way.. I don't know where to put those await and ToListAsync(). Thank you in advance!

Answer 1

The interface should be renamed to better show the intent.

public interface IDepRepository {
    Task<Department> GetDepartmentWithOrWithoutProductsAsync(int deptId, bool includeProducts);
    //...
}

Which would update the implementation accordingly. Since the method is not actually using anything after the async call then there not really any reason to tag the method as async. Just return the Task.

public Task<Department> GetDepartmentWithOrWithoutProductsAsync(int deptId, bool includeProducts) {
    if(includeProductss) {
        return db.Departments.Include(c => c.Products).Where(s => s.deptId == deptId).SingleAsync();
    }
    return db.Departments.Where(s => s.deptId == deptId).SingleAsync();
}

The controller action however needs to await the task and then continue after the task has completed so therefore that method will be tagged with async.

[HttpGet("{id}")]
public async Task<IActionResult> GetDepatment(int id, bool includeProducts = false) {
    var dept = await _deptInfoRepository.GetDepartmentWithOrWithoutProductsAsync(id, includeComputers);
    if (dept == null) {
        return BadRequest();
    }
    if (includeProducts) {
        var depResult =  new DepartmentDto() { deptId = dept.deptId, deptName = dept.deptName };
        foreach (var department in dept.Products) {
            depResult.Products.Add(new ProductDto() { 
                productId = department.productId, 
                deptId = department.deptId, 
                ProductName = department.ProductName 
            });
        } 
        return Ok(depResult);
    }
    var departmentWithoutProductResult = new DepartmentsWithoutProductsDto() { DeptId = dept.deptId, DeptName = dept.DeptName};
    return Ok(departmentWithoutProductResult);
}