按摩盒不显示 entity framework 核心

Question

嗨，我是 Microsoft entity framework 核心的新手，我使用（net core 3.1 和 Microsoft entity framework 核心）创建了一个简单的 windows 表单应用程序，我已经成功创建了一个 Table 看起来像这样

    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，我想向用户显示消息框“Name company already exists”并防止出现此错误（SqlException：违反 PRIMARY KEY 约束 'PK_Wholesalers'。无法插入重复项对象 'dbo.Wholesalers' 中的键。重复的键值为 ().)

Answer 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

按摩盒不显示 entity framework 核心

massage box not show entity framework core

c#

database

visual-studio

dbcontext

entity-framework-core