按摩框不显示实体框架核心[重复]

Posted 2023-03-28

【中文标题】按摩框不显示实体框架核心[重复]

【英文标题】：massage box not show entity framework core [duplicate]

【发布时间】：2020-09-01 16:10:36

【问题描述】：

嗨，我是 Microsoft 实体框架核心的新手，我使用（net core 3.1 和 Microsoft 实体框架核心）创建了一个简单的 Windows 窗体应用程序，我已经成功创建了一个看起来像这样的表

    using AplicationDbContext DbContext = new AplicationDbContext();
            Wholesaler tabPage = new Wholesaler()
            
                NameOwner = NameOwner.Text,
                NameCompany = NameCompany.Text,
                Address = Address.Text,
                MobilePhoneNumber1 =  MobilePhoneNumber1.Text,
                MobilePhoneNumber2 =  MobliePhoneNumber2.Text,
                linePhone1 = LinePhone1.Text,
                linePhone2 = LinePhone2.Text,
                Email = Email.Text,
                Fax = Fax.Text
            ;
DbContext.Wholesalers.Add(tabPage);
            DbContext.SaveChanges();

问题是 NameCompany Is PK，我想向用户显示按摩框“名称公司已存在”并防止出现此错误（SqlException：违反主键约束“PK_Wholesalers”。无法在对象中插入重复键“ dbo.Wholesalers'。重复键值为()。）

【参考方案1】：

using AplicationDbContext DbContext = new AplicationDbContext();
        
            Wholesaler tabPage = new Wholesaler()           
        
            NameOwner = NameOwner.Text,
            NameCompany = NameCompany.Text,
            Address = Address.Text,
            MobilePhoneNumber1 =  MobilePhoneNumber1.Text,
            MobilePhoneNumber2 =  MobliePhoneNumber2.Text,
            linePhone1 = LinePhone1.Text,
            linePhone2 = LinePhone2.Text,
            Email = Email.Text,
            Fax = Fax.Text
        ;
        if (DbContext.Wholesalers.Any(s => s.NameCompany == NameCompany.Text))
        
            MessageBox.Show($"Wholesaler: NameCompany.Text already exist ", "Name Company", MessageBoxButtons.OK, MessageBoxIcon.Information);
            return;
        
        DbContext.Wholesalers.Add(tabPage);
        DbContext.SaveChanges();
    

在这里找到答案Check if Record Exists in Entity Framework