c# - 使用实体框架注册

Question

所以我尝试使用实体框架和c#创建一个注册方法，这是方法：

//Button create new account
    private void BtnSignUp_Click(object sender, EventArgs e)
    {
        IEnumerable<DriverAcount> list = from a in context.DriverAcounts select a;
        foreach (var Ac in list)
        {
                if (TxBoxNewUserName.Text != Ac.Login)
                {
                    if (TxtBoxPASS1.Text == TxBoxPass.Text)
                    {
                        Ac.Login = TxBoxNewUserName.Text;
                        Ac.Password = TxtBoxPASS1.Text;
                        context.DriverAcounts.Add(Ac);
                        MessageBox.Show("the account is create succefuly");
                        TxBoxNewUserName.Text = "";
                        TxtBoxPASS1.Text = "";
                        TxBoxPass.Text = "";
                        break;
                    }

                    else
                    {
                        MessageBox.Show("the two passwords didn't matched");
                    }

                    TxBoxNewUserName.Text = "";
                    TxtBoxPASS1.Text = "";
                    TxBoxPass.Text = "";
                    continue;
                }
            else
            {
                MessageBox.Show("this username is already exist, please choose another one");
                TxBoxNewUserName.Text = "";
                TxtBoxPASS1.Text = "";
                TxBoxPass.Text = "";
                break;
            }

        }
        context.SaveChanges();
    }

问题是当我想正常添加一个新用户时，它应该查看它是否存在于数据库中，但它没有做对，例如，如果我们在 DB name1和name2中有两个名称，并进入我们有的 TextBox name2它将在 DB 中添加name2，即使它已经存在。因此，如果有人有想法，我将不胜感激。

Answer 1

您需要再次查看您的代码并准确了解它在做什么——您是否附加了调试器并逐步完成了它？foreach如果检索到的第一个名称与文本框中的名称不匹配，则始终会在循环的第一次迭代中创建驱动程序名称。所有其他将被忽略。

你可以试试这个。当您只想检查一个是否已经存在时，无需查询所有记录（就像您现在正在做的那样）。

private void BtnSignUp_Click(object sender, EventArgs e)
{
    // This performs a case sensitive match on the login name, you'll need to change it if you want to ignore case
    DriverAcount existingAccount = context.DriverAcounts.FirstOrDefault(d => d.Login == TxBoxNewUserName.Text);

    if (existingAccount != null)
    {
            MessageBox.Show("This username already exists, please choose another one.");
    }
    else
    {
            if (TxtBoxPASS1.Text == TxBoxPass.Text)
            {
                    Ac.Login = TxBoxNewUserName.Text;
                    Ac.Password = TxtBoxPASS1.Text;
                    context.DriverAcounts.Add(Ac);

                    // Only need to call this if you've made changes, so I've moved it here
                    context.SaveChanges();

                    MessageBox.Show("The account was created successfully");
            }
            else
            {
                    MessageBox.Show("The two passwords didn't match each other.");
            }
    }

    TxBoxNewUserName.Text = "";
    TxtBoxPASS1.Text = "";
    TxBoxPass.Text = "";
}