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रिपोजिटरी पैटर्न System.NullReferenceException में
हटाएँ विधि
System.NullReferenceException
HRपरिणाम=0x80004003
संदेश=ऑब्जेक्ट संदर्भ किसी ऑब्जेक्ट के उदाहरण पर सेट नहीं है।
स्रोत=Microsoft.EntityFrameworkCore
स्टैक ट्रेस:
Microsoft.EntityFrameworkCore.Internal.EntityFinder`1.ValidateKeyPropertiesAndExtractCancelationToken(Object) पर[] keyValues, बूलियन एसिंक्स, कैंसिलेशनटोकन कैंसिलेशनटोकन)
Microsoft.EntityFrameworkCore.Internal.EntityFinder`1.Find(Object) पर[] कुंजीमूल्य)
BL.Repositories.BaseRepository`1.GetById(Nullable`1 id) पर E:\Programming\Folder\SoqRepository\BL\Repositories\BaseRepository.cs:line 51
मैंने क्या प्रयास किया है:
डेटाबेस से कक्षा
using System; using System.Collections.Generic; namespace Sq.Models; public partial class VwItem { public string ItemName { get; set; } = null!; public decimal PurchasePrice { get; set; } public decimal SalesPrice { get; set; } public int CategoryId { get; set; } public string? ImageName { get; set; } public DateTime CreatedDate { get; set; } public string CreatedBy { get; set; } = null!; public int CurrentState { get; set; } public string? UpdatedBy { get; set; } public DateTime? UpdatedDate { get; set; } public string? Description { get; set; } public string? Gpu { get; set; } public string? HardDisk { get; set; } public int? ItemTypeId { get; set; } public string? Processor { get; set; } public int? RamSize { get; set; } public string? ScreenReslution { get; set; } public string? ScreenSize { get; set; } public string? Weight { get; set; } public int? OsId { get; set; } public string CategoryName { get; set; } = null!; public string ItemTypeName { get; set; } = null!; public string OsName { get; set; } = null!; public int ItemId { get; set; } }
क्लास इंटरफ़ेस
using Sq.Models; using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace Domain.Interfaces { public interface IBaseRepository <t> where T : class { public IEnumerable<t>GetAll(); public IEnumerable<t> GetAll(Func<t, bool=""> Condition); public T GetById(int? id); public void Delete(T Entity); public void ChangeState(int id); } }
using Domain.Interfaces; using Sq.BL; using Sq.Models; using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace BL.Repositories { public class BaseRepository<t> : IBaseRepository<t> where T : class { public LapShopContext LapShopContext; public BaseRepository(LapShopContext _LapShopContext) { LapShopContext = _LapShopContext ?? throw new ArgumentNullException(nameof(_LapShopContext)); }
इंटरफ़ेस लागू करें
using Sq.Models; using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace Domain.Interfaces { public interface IBaseRepository <t> where T : class { public T GetById(int? id); public void Delete(T Entity); } } public T GetById(int? id) { try { return LapShopContext.Set<t>().Find(id); } catch (Exception) { return null; } } public void Delete(T entity) { try { LapShopContext.Set<t>().Remove(entity); LapShopContext.SaveChanges(); } catch (Exception) { return; } }
नियंत्रक
public ActionResult Delete(int ItemId) { if (ItemId == null) { return BadRequest("ItemId is null"); } var Obj = baseRepository.GetById(ItemId); baseRepository.Delete(Obj); return RedirectToAction("List"); }
समाधान 1
त्रुटि संदेश के रूप में, समस्या हटाएँ विधि में है। डिलीट विधि LapShopContext.Set
public ActionResult Delete(int ItemId) { if (ItemId == 0) { return BadRequest("ItemId is invalid"); } var Obj = baseRepository.GetById(ItemId); if (Obj == null) { return NotFound($"Item with ID {ItemId} not found"); } baseRepository.Delete(Obj); return RedirectToAction("List"); }
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