CODEWITHSUNDEEP
c#.net-coretaskactionresult
Chuck Duncan
Chuck Duncan

Reputation: 23

Can't convert 'System.Threading.Tasks.Task<Microsoft.AspNetCore.Mvc.ActionResult<System.Collections.Generic ... to System.Collections.Generic

Though some answers are in this area, none answer my question. This function is a part of a Projects repository. Projects have a lot of items, but there are times when only the "Header" elements are needed from it. The Header is NOT stored separately, but has a different "API..Dto". (This has to get shipped back to the front-end)

public async Task<ActionResult<List<ProjectAPIHeaderDto>>> GetAllProjectHeaders()
{
    var projects = await _context.Projects.ToListAsync();  // full project records
    var records = _mapper.Map<List<ProjectAPIHeaderDto>>(projects);  // only some fields from project
    return records;
}

The problem is:

Cannot implicitly convert type 'System.Threading.Tasks.Task<Microsoft.AspNetCore.Mvc.ActionResult<System.Collections.Generic.List<API.DTOs.ProjectAPIHeaderDto>>>' to 'System.Collections.Generic.List<API.DTOs.ProjectAPIHeaderDto>'

Similar code works perfectly in another function shown here:

public async Task<List<ProjectAPIDto>> GetAllProjects()
{
    var projects = await _context.Projects.ToListAsync();
    var records = _mapper.Map<List<ProjectAPIDto>>(projects);
    return records;
}

ProjectAPIDto has all fields from the projects while ProjectAPIHeaderDto has a few of the project fields.

This link is hover over var records and shows it is List. enter image description here

this is ProjectAPIHeaderDto:

using System.ComponentModel.DataAnnotations;

namespace API.DTOs
{
    public class ProjectAPIHeaderDto
    {
        public int Id { get; set; }
        [Required]
        public string Title { get; set; }
        [Required]
        public string Description { get; set; }

    }
}

Looking again at the error message: System.Threading.Tasks.Task<Microsoft.AspNetCore.Mvc.ActionResult I've never seen this problem before anywhere.. is ActionResult the problem?

Thanks in advance for your help.

Upvotes: 2

Views: 709

Answers (1)

Martin
Martin

Reputation: 3286

Try to use Task<IActionResult> instead and wrap your result in an Ok(...) (or whatever is needed in your response).

public async Task<IActionResult> GetAllProjectHeaders()
{
    var projects = await _context.Projects.ToListAsync();  // full project records
    var records = _mapper.Map<List<ProjectAPIHeaderDto>>(projects);  // only some fields from project
    return Ok(records);
}

Here you can find a good comparison of the three options.

Note: If your are using any kind of client generation tool (Nswag, Swashbuckle, ...) you need to specify a response type attribute because the IActionResult has no T

Upvotes: 0

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