EF 一个简单的使用
1、创建的控制台程序,NuGet引用了EF。 里面用了序列号,需要引用Newtonsoft.Json
2、数据库用的现成的,已经有表和数据了。数据库名MyDbContext,表Students
3、在app.config中添加配置项,添加到configSections这个节点后面,和它同级。
<connectionStrings> <add name="MyDbContext" connectionString="Data Source=.\sqlexpress;Database=MyDbContext;UID=sa;PWD=sa;" providerName="System.Data.SqlClient"></add> </connectionStrings>
全部代码
基本使用
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//基本使用 public class Class4 { public void test1() { Console.WriteLine(123); using (var db = DbFactory.Create()) { //db.... //db.SaveChange(); //测试1 打印students表的所有数据 var list = db.All<Students>().ToList(); var str = JsonConvert.SerializeObject(list); Console.WriteLine(str); //测试2 添加一个学生 Students student1 = new Students { Name = "name12", Age = 12, }; db.Insert<Students>(student1); db.SaveChanges(); } } }
自定义代码
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//自定义代码 public class Students { public int Id { get; set; } public string Name { get; set; } public int Age { get; set; } public DateTime? CreateTime { get; set; } } public class MyDbContext : DbContext { public MyDbContext(string connectionName) : base(connectionName) { } public DbSet<Students> Orders { get; set; } }
通用代码 引用了 MyDbContext
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//原文:https://www.cnblogs.com/leotsai/p/entity-framework-doesnt-need-additional-repository.html //花猫.NET的评论里面的代码 //通用代码 引用了 MyDbContext public class DbFactory { public static IRepository Create() { return new EfRepository(new MyDbContext("MyDbContext")); } } public interface IRepository : IDisposable { int SaveChanges(); IQueryable<T> All<T>() where T : class; T Get<T>(Expression<Func<T, bool>> conditions) where T : class; void Insert<T>(T entity) where T : class; void Update<T>(T entity) where T : class; void Delete<T>(T entity) where T : class; void Delete<T>(Expression<Func<T, bool>> conditions) where T : class; List<T> Find<T>(Expression<Func<T, bool>> conditions = null) where T : class; List<T> Find<T, S>(Expression<Func<T, bool>> conditions, Expression<Func<T, S>> orderBy, int pageSize, int pageIndex, out int totalCount) where T : class; List<T> SqlQuery<T>(string sql); int ExecuteSqlCommand(string sql); long GetNextSequenceValue(string sequenceName); } public class EfRepository : IRepository { private DbContext context; public EfRepository(DbContext dbcontext) { context = dbcontext; } #region IRepository public IQueryable<T> All<T>() where T : class { return context.Set<T>().AsNoTracking(); } public void Update<T>(T entity) where T : class { var entry = context.Entry(entity); if (entry.State == EntityState.Detached) { context.Set<T>().Attach(entity); } entry.State = EntityState.Modified; } public void Insert<T>(T entity) where T : class { context.Set<T>().Add(entity); } public void Delete<T>(T entity) where T : class { var entry = context.Entry(entity); if (entry.State == EntityState.Detached) { context.Set<T>().Attach(entity); } entry.State = EntityState.Deleted; context.Set<T>().Remove(entity); } public void Delete<T>(Expression<Func<T, bool>> conditions) where T : class { var list = Find<T>(conditions); foreach (var item in list) { Delete<T>(item); } } public T Get<T>(Expression<Func<T, bool>> conditions) where T : class { return All<T>().FirstOrDefault(conditions); } public List<T> Find<T>(Expression<Func<T, bool>> conditions = null) where T : class { if (conditions != null) { return All<T>().Where(conditions).ToList(); } else { return All<T>().ToList(); } } public List<T> Find<T, S>(Expression<Func<T, bool>> conditions, Expression<Func<T, S>> orderBy, int pageSize, int pageIndex, out int totalCount) where T : class { var queryList = conditions == null ? All<T>() : All<T>().Where(conditions); totalCount = queryList.Count(); return queryList.OrderByDescending(orderBy).Skip((pageIndex - 1) * pageSize).Take(pageSize).ToList(); } public List<T> SqlQuery<T>(string sql) { return context.Database.SqlQuery<T>(sql).ToList(); } public int ExecuteSqlCommand(string sql) { return context.Database.ExecuteSqlCommand(sql); } public int SaveChanges() { return context.SaveChanges(); } public void Dispose() { context.Dispose(); } public long GetNextSequenceValue(string sequenceName) { var rawQuery = context.Database.SqlQuery<long>(string.Format("SELECT NEXT VALUE FOR {0}", sequenceName)).ToList(); long nextVal = rawQuery.Single(); return nextVal; } #endregion }