如何排序EntitySet< T> [英] How do you sort an EntitySet<T>

问题描述

MSDN文档指出，EntitySet实现IBindingList

The MSDN documentation states that an EntitySet implements IBindingList

（请参阅 http://msdn.microsoft.com/en-us/library/bb546190.aspx ）

但是，可以清楚地看到，EntitySet不实现这个界面！

However, it can be clearly seen that an EntitySet does not implement this interface!

那么我如何排序？

对于上下文，我将此集合绑定到WPF ListView。

For context, I'm binding this set to a WPF ListView.

对于更广泛的问题，我想解决的问题，请参见这篇文章。

For wider context of problem I'm trying to solve please see this post.

推荐答案

EntitySet< T>不实现IBindingList ...它提供了一种获取IBindingList的方法。您需要调用.GetNewBindingList（）来获取EntitySetBindingList< T>的实例，该实例来自SortableBindingList< T>，其是BindingList< T>。 EntitySetBindingList只是原始EntitySet< T>它是由...创建的，所以对其进行的任何修改都是对原始EntitySet的修改。

EntitySet<T> doesn't implement IBindingList...it provides a method to get an IBindingList. You need to call .GetNewBindingList() to get an instance of EntitySetBindingList<T>, which derives from SortableBindingList<T>, which is a BindingList<T>. EntitySetBindingList is just a wrapper around the original EntitySet<T> it was created from, so any modifications to it are modifications to the original EntitySet.

编辑：使用BindingList排序：

Sorting with BindingList:

要使用BindingList进行排序，您需要公开某种界面以允许排序。 BindingList< T>中支持排序类，但它通过受保护的属性和方法。应该可以使用包装器公开一个表达式的排序方法：

To sort with a BindingList, you need to expose some kind of interface to allow sorting. Sorting is supported within the BindingList<T> class, but its through protected properties and methods. It should be possible to expose an expressive sort method with a wrapper:

public class EntitySetBindingWrapper<T>: BindingList<T>
{
    public EntitySetBindingWrapper(BindingList<T> root) : base(root)
    {
    }

    public void Sort(Expression<Func<T, P>> expr, ListSortDirection direction)
    {
        if (expr == null)
            base.RemoveSortCore();

        MemberExpression propExpr = expr as MemberExpression;
        if (propExpr == null) throw new ArgumentException("You must provide a property", "expr");

        PropertyDescriptorCollection descriptorCol = TypeDescriptor.GetProperties(typeof(T));
        IEnumerable<PropertyDescriptor> descriptors = descriptorCol.Cast<PropertyDescriptor>();
        PropertyDescriptor descriptor = descriptors.First(pd => pd.Name == propExpr.Member.Name);

        base.ApplySortCore(descriptor, direction);
    }
}

您应该可以像这样排序： / p>

You should then be able to sort like so:

var bindingWrapper = new EntitySetBindingWrapper(myEntitySet.GetNewBindingList());
bindingWrapper.Sort(e => e.MyProperty, ListSortDirection.Ascending);

listView.DataSource = bindingWrapper;

对于EntitySetBindingWrapper类，可能还有其他实现，例如在BindingList< ; T>给提供给构造函数的一个。

There might be additional implementation for the EntitySetBindingWrapper class...such as fortwarding any normally public methods on BindingList<T> to the one provided to the constructor.

这篇关于如何排序EntitySet&lt; T&gt;的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！