c# - 在 ASP.NET MVC 3 中初始化一个空白 dbSet

Question

我在语句中定义一个变量if，然后尝试在该语句的上下文之外使用该变量。如何dbSet在 if 语句之外初始化一个空的，以便viewModel可以看到/填充它？

这就是我想要完成的事情：

if (order.type.ToString() == "Rush")
{
    var filteredOrders = db.Orders.Where(a => a.rushID == order.rushID).ToList(); 
}
else if (order.type.ToString() == "Standard")
{
    var filteredOrders = db.Orders.Where(a => a.standardID == order.standardID).ToList();
}
else
{
    return HttpNotFound();
}

var viewModel = new OrderDetailsViewModel
{
    PastOrders = filteredOrders,  // filteredOrders doesn't exist here
    Order = order;
};

Answer 1

IEnumerable<Order> filteredOrders; // or IList<Order>, etc., as your prefer

switch (order.type.ToString())
{
    case "Rush":
        filteredOrders = db.Orders.Where(a => a.rushID == order.rushID).ToList();
    case "Standard":
        filteredOrders = db.Orders.Where(a => a.standardID == order.standardID).ToList();
    default::
        return HttpNotFound();
}

var viewModel = new OrderDetailsViewModel
{
    PastOrders = filteredOrders,
    Order = order;
};

---

或更好：

Func<Order, bool> filter;

switch (order.type.ToString())
{
    case "Rush":
        filter = a => a.rushID == order.rushID;
    case "Standard":
        filter = a => a.standardID == order.standardID;
    default::
        return HttpNotFound();
}

var viewModel = new OrderDetailsViewModel
{
    PastOrders = db.Orders.Where(filter).ToList(),
    Order = order;
};