How to resolve the error 'System.Int32' type to the 'System.String' type is not valid in mvc api ?

Hi

I have an error 'System.Int32' type to the 'System.String' type is not valid in mvc api .

Pls advice me

Thank you
Maideen

It is my code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace advEditorials.Models
{
    public class MoDetails
    {
        public int Id { get; set; }
        public string DocNo { get; set; }
        public DateTime PubDate { get; set; }
        public string MainSection { get; set; }
        public string SubSection { get; set; }
        public string Position { get; set; }
        public string Color { get; set; }
        public decimal SizeH { get; set; }
        public decimal SizeW { get; set; }
        public decimal Volume { get; set; }
        public decimal PageNumber { get; set; }
        public string Materials { get; set; }
        public string Remarks { get; set; }
        public string Status { get; set; }

    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Web;

namespace advEditorials.Models
{
    public interface IMORepository
    {
        Task Add(MoDetails mo);
        Task Update(MoDetails mo);
        Task Delete(string id);
        Task<MoDetails> Getmo(string id);
        Task<IEnumerable<MoDetails>> GetmoALL();
    }
}

using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Threading.Tasks;
using System.Web;

namespace advEditorials.Models
{
    public class MORepository :IMORepository
    {
        private readonly SqlDbContext db = new SqlDbContext();

// Retrive All
        public async Task<IEnumerable<MoDetails>> GetmoALL()
        {
            try
            {
                var mo = await db.tbl_Editorial.ToListAsync();
                return mo.AsQueryable();
            }
            catch
            {
                throw;
            }
        }

 // by ID
        public async Task<MoDetails> Getmo(string id)
        {
            try
            {
                MoDetails mo = await db.tbl_Editorial.FindAsync(id);
                if (mo == null)
                {
                    return null;
                }
                return mo;
            }
            catch
            {
                throw;
            }
        }
 //Add
        public async Task Add(MoDetails mo)
        {
            mo.Id = Guid.NewGuid().ToString();
            db.tbl_Editorial.Add(mo);
            try
            {
                await db.SaveChangesAsync();
            }
            catch
            {
                throw;
            }
        }

        //Update
        public async Task Update(MoDetails mo)
        {
            try
            {
                db.Entry(mo).State = EntityState.Modified;
                await db.SaveChangesAsync();
            }
            catch
            {
                throw;
            }
        }
//Delete
        public async Task Delete(string id)
        {
            try
            {
                MoDetails mo = await db.tbl_Editorial.FindAsync(id);
                db.tbl_Editorial.Remove(mo);
                await db.SaveChangesAsync();
            }
            catch
            {
                throw;
            }
        }

        private bool MOExists(string id)
        {
            return db.tbl_Editorial.Count(e => e.Id == id) > 0;
        }
    }
} 

Controller

using advEditorials.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Threading.Tasks;
using System.Web.Http;

namespace advEditorials.Controllers
{
    public class EditorialController : ApiController
    {
        private readonly IMORepository _iMORepository = new MORepository();

        [HttpGet]
        //[Route("api/Editorial/Get")]
        public async Task<IEnumerable<MoDetails>> Get()
        {
            return await _iMORepository.GetmoALL();
        }

        [HttpPost]
        [Route("api/Editorial/Create")]
        public async Task CreateAsync([FromBody]MoDetails mo)
        {
            if (ModelState.IsValid)
            {
                await _iMORepository.Add(mo);
            }
        }

        [HttpGet]
        [Route("api/Editorial/Details/{id}")]
        public async Task<MoDetails> Details(string id)
        {
            var result = await _iMORepository.Getmo(id);
            return result;
        }

        [HttpPut]
        [Route("api/Editorial/Edit")]
        public async Task EditAsync([FromBody]MoDetails mo)
        {
            if (ModelState.IsValid)
            {
                await _iMORepository.Update(mo);
            }
        }

        [HttpDelete]
        [Route("api/Editorial/Delete/{id}")]
        public async Task DeleteConfirmedAsync(string id)
        {
            await _iMORepository.Delete(id);
        }
    }
}

db Table

CREATE TABLE [dbo].[tbl_Editorial](
	[id] [nvarchar](20) NOT NULL,
	[DocNo] [varchar](20) NULL,
	[pubdate] [date] NULL,
	[MainSection] [varchar](50) NULL,
	[SubSection] [varchar](50) NULL,
	[Position] [varchar](50) NULL,
	[Color] [varchar](20) NULL,
	[SizeH] [float] NULL,
	[SizeW] [float] NULL,
	[Volume] [float] NULL,
	[PageNumber] [float] NULL,
	[Materials] [varchar](100) NULL,
	[Remarks] [varchar](100) NULL,
	[Status] [varchar](20) NULL,
	[Category] [varchar](50) NULL
) ON [PRIMARY]
GO