如何从C＃MVVM中绑定到ObservableCollection的列表中删除对象

Question

I'm trying to use the MVVM pattern in C#. Therefore I have a customer class:

public class Customer
{
    public string CustumerNumber { get; set; }
    public string CustomerName { get; set; }
}

I fill a list with Customers from a database:

public class CustomerList
{
    public static List<Customer> customerlist = new List<Customer>();

    public static List<Customer> GetCustomer()
    {
    // Get data from database
    }
}

My ViewModel:

class ViewModel : BaseViewModel
{
    public ObservableCollection<Customer> Customers { get; set; }
    public string CustomerSearch { get; set; }

    public ViewModel()
    {
         Customers = new ObservableColletion<Customers>(CustomerList.GetCustomer());
    }
}

I bound Customers in an WPF-ListBox:

<ListBox ItemsSource="{Binding Customers}"
DisplayMemberPath="CustomerName"/>

Let's say I have 10 objects of CustomerName in the ListBox. There is a TextBox that contains a string. Now I want to remove all objects in the ListBox that don't contain the string. I solved the problem in the ViewModel as follows:

public void SearchCustomer()
{
    foreach (Customer item in Customers)
    {
        if (item.Customers.ToUpper().Contains(CustomerSearch.ToUpper()) == false)
        {
            this.Customers = new ObservableCollection<Customer>(CustomerList.RemoveItemsFromView(item));
        }
    }
}

Is this right? It feels wrong to me, because every time the loop removes an item I create a new ObservableCollection instead of manipulating the existing one. Is there a more professional way to solve this task?

For the PropertyChangeEvent I use FodyWeaver

Answer 1

由于您已经拥有“客户”项目，因此您可以在以下情况下执行此操作：

this.Customers.Remove(item) 

Answer 2

You should use the method Remove from Customers like you are doing with CustomerList . Or update Customers after the loop:

First Option

foreach (Customer customer in Customers)
{
    if (!customer.Customers.ToUpper().Contains(CustomerSearch.ToUpper()))
    {
        CustomerList.RemoveItemsFromView(customer);
        Customers.Remove(customer);
    }
}

Second Option

foreach (Customer customer in Customers)
{
    if (!customer.Customers.ToUpper().Contains(CustomerSearch.ToUpper()))
    {
        CustomerList.RemoveItemsFromView(customer);
    }
}

this.Customers = new ObservableCollection<Customer>(CustomerList);

I can't suggest you more options without havig CustomerList and RemoveItemsFromView source code.

Also, I refactored a bit the code. Having a good name for variables is important. And if looks a bit wrong, but I don't have your model.

Answer 3

If you don't want to create a new source collection, you could remove items from the existing one. Just make sure that you don't call the Remove method in a foreach loop.

This should work:

for (int i = Customers.Count - 1; i >= 0; i--)
{
    Customer item = Customers[i];
    if (item.Customers.ToUpper().Contains(CustomerSearch.ToUpper()) == false)
    {
        Customers.RemoveAt(i);
    }
}

If you do reset the collection property each time you want to add or remove an item, you might as well use a List<T> . Just make sure that you raise a property notification when the property is set.