Question

我是实体框架的新手。我试图找到将我的选择值返回到我的实体属性的最佳代码这是我的代码：

private void CustomerForm_Load(object sender, EventArgs e)
    {
        if (CustomerID != null && CustomerMode !=(int)CustomerModeOperaton.insert)
        {
            using (var Context = new FactorEntities())
            {
                    var Customercods =  from _customers in Context.tblCustomers.Where(c => c.CustomerID == CustomerID) select _customers.CustomerCode;
                    _tblCustomer.CustomerCode = Customercods.First();
                    var Customernames = from _customers in Context.tblCustomers.Where(c => c.CustomerID == CustomerID) select _customers.CustomerName;
                    _tblCustomer.CustomerName = Customernames.First();
                    var Customerlastname = from _customers in Context.tblCustomers.Where(c => c.CustomerID == CustomerID) select _customers.CustomerLastName;
                    _tblCustomer.CustomerLastName = Customerlastname.First();
                    var customerID = from _customers in Context.tblCustomers.Where(c => c.CustomerID == CustomerID) select _customers.CustomerID;
                    _tblCustomer.CustomerID = customerID.First();
                    var customerAddresses = from _customers in Context.tblCustomers.Where(c => c.CustomerID == CustomerID) select _customers.CustomerAdresse;
                    _tblCustomer.CustomerAdresse = customerAddresses.First();
                    var customerMobile = from _customers in Context.tblCustomers.Where(c => c.CustomerID == CustomerID) select _customers.CustomerCellPhone;
                    _tblCustomer.CustomerCellPhone = customerMobile.First();
                    var customerphone = from _customers in Context.tblCustomers.Where(c => c.CustomerID == CustomerID) select _customers.CustomerPhone;
                    _tblCustomer.CustomerPhone = customerphone.First();

            }

        }

        LoadDataToControl();
}

但是我想知道我是否使用这个代码，我必须使用几个不好的选择，如果我的选择值为null，我该怎么办？例如这段代码：

_tblCustomer.CustomerPhone = customerphone.First();

Answer 1

您只需要查询一次客户，并让其在一个对象中返回所有客户的信息。然后，您可以仅为_tblCustomer字段的作业引用该对象的属性。

如果您使用FirstOrDefault，那么您可以在尝试使用之前检查返回的对象是否为null（如果没有与CustomerID匹配的客户一个你的搜索）：

var customer = Context.tblCustomers.FirstOrDefault(c => c.CustomerID == CustomerID);

if (customer != null)
{
    _tblCustomer.CustomerCode = customer.CustomerCode; 
    _tblCustomer.CustomerName = customer.CustomerName;
    _tblCustomer.CustomerLastName = customer.CustomerLastName;
    _tblCustomer.CustomerID = customer.CustomerID;
    _tblCustomer.CustomerAdresse = customer.CustomerAdresse;
    _tblCustomer.CustomerCellPhone = customer.CustomerCellPhone;
    _tblCustomer.CustomerPhone = customer.CustomerPhone;
}

我们如何将select值返回给实体的每个属性？

1 个答案: