Entity framwork 学习(1)

最新推荐文章于 2025-05-14 15:20:02 发布

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#exception #object #null #delete

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本文通过 C# 代码示例介绍了如何使用 ORM 技术实现数据库的增删改查操作，包括事务处理，并展示了如何获取数据源。

private void btnAdd_Click(object sender, EventArgs e) { try { using (var db = new DemoEntities()) { Account entity = new Account(); entity.Name = "Lucy"; entity.Pwd = "1234"; entity.Age = 50; entity.IsMarry = true; db.AddToAccount(entity); int result = db.SaveChanges(); if (result == 1) { MessageBox.Show("Add account success"); } } } catch (Exception ex) { MessageBox.Show(ex.Message); } } private void btnModify_Click(object sender, EventArgs e) { try { using (var db = new DemoEntities()) { int id = int.Parse(this.txtID.Text); Account entity = db.Account.FirstOrDefault(tbEntity => tbEntity.Id == id); entity.Name = "MiMi"; entity.Pwd = "abcd"; entity.Age = 30; entity.IsMarry = true; int result = db.SaveChanges(); if (result == 1) { MessageBox.Show("Modify account success"); } } } catch (Exception ex) { MessageBox.Show(ex.Message); } } private void btnDelete_Click(object sender, EventArgs e) { try { using (var db = new DemoEntities()) { int id = int.Parse(this.txtID.Text); Account entity = db.Account.FirstOrDefault(tbEntity => tbEntity.Id == id); db.DeleteObject(entity); int result = db.SaveChanges(); if (result == 1) { MessageBox.Show("Delete account success"); } } } catch (Exception ex) { MessageBox.Show(ex.Message); } } private void btnGetDataSource_Click(object sender, EventArgs e) { using (var db = new DemoEntities()) { //(1)List<Account> accountList = db.Account.ToList<Account>(); List<Account> accountList = (from account in db.Account select account).ToList<Account>(); this.dgDriver.DataSource = accountList; } } private void btnTransaction_Click(object sender, EventArgs e) { DemoEntities db = null; System.Data.Common.DbTransaction tran = null; try { db = new DemoEntities(); db.Connection.Open(); tran = db.Connection.BeginTransaction(); List<Account> entityList = db.Account.ToList<Account>(); foreach (Account entity in entityList) { entity.Name = "liming"; entity.Age = 10; int result = db.SaveChanges(); if (result != 1) { throw new Exception("Modify Account Error,account Id=" + entity.Id.ToString()); } } tran.Commit(); MessageBox.Show("Transaction operate success"); } catch (Exception ex) { MessageBox.Show(ex.Message); } }