Generic Interface And Generic Repository For Developing ASP.NET Core Web API

Step 1. Define the Base Entity

First, you need to define Base Entity in your Domain Layer,

Generic Interface and Generic Repository for Developing Asp.net Core Web API

Code for Base Entity

public class BaseEntity {
    public int Id {
        get;
        set;
    }
    public int UsesId {
        get;
        set;
    }
    public int CreatedBy {
        get;
        set;
    }
    public int CompanyId {
        get;
        set;
    }
    public DateTime CreatedDate {
        get;
        set;
    } = DateTime.Now;
    public DateTime ModifiedDate {
        get;
        set;
    }
    public bool IsDeleted {
        get;
        set;
    }
}

Step 2. Define the Generic IRepository

Define the Generic Interface in your Repository Layer as shown in the picture,

Generic Interface and Generic Repository for Developing Asp.net Core Web API

Code for IRepository

using AC_Contact_API_Service_Layer.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection.Emit;
using System.Text;
using System.Threading.Tasks;
namespace AC_Contact_API_Repository_Layer.IRepository {
    public interface IRepository < T > where T: BaseEntity {
        IEnumerable < T > GetAll();
        T Get(int Id);
        void Insert(T entity);
        void Update(T entity);
        void Delete(T entity);
        void Remove(T entity);
        void SaveChanges();
    }
}

Step 3. Define the Generic Repository

Define the Generic Repository In your Repository Layer Using the Onion Architecture,

Generic Interface and Generic Repository for Developing Asp.net Core Web API

Code For Generic Repository

using AC_Contact_API_Repository_Layer.IRepository;
using AC_Contact_API_Service_Layer.App_Data;
using AC_Contact_API_Service_Layer.Models;
using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace AC_Contact_API_Repository_Layer.Repository {
    public class Repository < T > : IRepository < T > where T: BaseEntity {
        #region property
        private readonly ApplicationDbContext _applicationDbContext;
        private DbSet < T > entities;
        #endregion
        #region Constructor
        public Repository(ApplicationDbContext applicationDbContext) {
            _applicationDbContext = applicationDbContext;
            entities = _applicationDbContext.Set < T > ();
        }
        #endregion
        public void Delete(T entity) {
            if (entity == null) {
                throw new ArgumentNullException();
            } else {
                entities.Remove(entity);
                _applicationDbContext.SaveChanges();
            }
        }
        public T Get(int Id) {
            try {
                if (Id == null) {
                    throw new ArgumentNullException();
                } else {
                    return entities.SingleOrDefault(c => c.Id == Id);
                }
            } catch (Exception ex) {
                throw new Exception(ex.Message);
            }
        }
        public IEnumerable < T > GetAll() {
            return entities.AsEnumerable();
        }
        public void Insert(T entity) {
            if (entity == null) {
                throw new ArgumentNullException("entity");
            }
            entities.Add(entity);
            _applicationDbContext.SaveChanges();
        }
        public void Remove(T entity) {
            if (entity == null) {
                throw new ArgumentNullException("entity");
            }
            entities.Remove(entity);
        }
        public void SaveChanges() {
            _applicationDbContext.SaveChanges();
        }
        public void Update(T entity) {
            if (entity == null) {
                throw new ArgumentNullException("entity");
            }
            entities.Update(entity);
            _applicationDbContext.SaveChanges();
        }
    }
}

Conclusion

In API (Application Programming Interface) development, the term "generic" refers to a type or method that can work with values of any data type rather than being restricted to a specific data type. Generics allow you to write flexible, reusable code that can be applied to different data types, making your API more versatile and easier to maintain. For example, a generic list in a programming language such as Java or C# can be defined to hold elements of any type, making it useful for various tasks rather than creating separate lists for different data types.

If you want to study Onion Architecture, follow the link below,

Onion Architecture In ASP.NET Core 6 Web API