我可以暂时禁用WPF数据绑定更改吗？ [英] Can I somehow temporarily disable WPF data binding changes?

问题描述

我有一个使用MVVM数据绑定的WPF应用程序。我将项目添加到 ObservableCollection< ...> 中，其中很多都是。

现在我我想知道每当我加入一个收藏，它会立即触发事件并造成不必要的开销？如果是这样，我可以暂时禁用事件通知，并在我的代码末尾手动触发一次，以便如果我添加10k项目，它只会被触发一次，而不是10k次？

更新：我尝试过这个类：

  using System; 
使用System.Linq; 
使用System.Collections.Specialized; 
使用System.Collections.Generic; 
 
命名空间MyProject 
 {
 
 ///< summary> 
 ///表示一个动态数据集合，当项目被添加，删除或整个列表刷新时提供通知。 
 ///< / summary> 
 ///< typeparam name =T>< / typeparam> 
 public class ObservableCollection< T> ：System.Collections.ObjectModel.ObservableCollection< T> 
 {
 
 ///< summary> 
 ///将指定集合的​​元素添加到ObservableCollection（Of T）的末尾。 
 ///< / summary> 
 public void AddRange（IEnumerable< T>集合）
 {
 foreach（var i in collection）Items.Add（i）; 
 OnCollectionChanged（new NotifyCollectionChangedEventArgs（NotifyCollectionChangedAction.Add，collection.ToList（）））; 
} 
 
 ///< summary> 
 ///从ObservableCollection（Of T）中删除指定集合中每个项目的第一次发生。 
 ///< / summary> 
 public void RemoveRange（IEnumerable< T>集合）
 {
 foreach（var i in collection）Items.Remove（i）; 
 OnCollectionChanged（new NotifyCollectionChangedEventArgs（NotifyCollectionChangedAction.Remove，collection.ToList（）））; 
} 
 
 ///< summary> 
 ///清除当前集合并将其替换为指定的项目。 
 ///< / summary> 
 public void Replace（T item）
 {
 ReplaceRange（new T [] {item}）; 
} 
 ///< summary> 
 ///清除当前集合并将其替换为指定的集合。 
 ///< / summary> 
 public void ReplaceRange（IEnumerable< T>集合）
 {
列表< T> old = new List< T>（Items）; 
 Items.Clear（）; 
 foreach（var i in collection）Items.Add（i）; 
 OnCollectionChanged（new NotifyCollectionChangedEventArgs（NotifyCollectionChangedAction.Replace，collection.ToList（）））; 
} 
 
 ///< summary> 
 ///初始化System.Collections.ObjectModel.ObservableCollection（Of T）类的新实例。 
 ///< / summary> 
 public ObservableCollection（）：base（）{} 
 
 ///< summary> 
 ///初始化包含从指定集合复制的元素的System.Collections.ObjectModel.ObservableCollection（Of T）类的新实例。 
 ///< / summary> 
 ///< param name =collection> collection：复制元素的集合。< / param> 
 ///< exception cref =System.ArgumentNullException> collection参数不能为空。< / exception> 
 public ObservableCollection（IEnumerable< T>集合）：base（collection）{} 
} 
} 
  

我现在收到这个错误：

附加信息：不支持范围操作。

错误出现在这里：

  OnCollectionChanged new NotifyCollectionChangedEventArgs（NotifyCollectionChangedAction.Add，collection.ToList（）））; 
  

解决方案

一个非常快速和容易的方法是将ObservableCollection和当调用AddRange时挂起通知。有关澄清，请参阅以下博客文章。

I have a WPF application that uses MVVM data bindings. I am adding items to an ObservableCollection<...> and quite many of them indeed.

Now I am wondering that every time I add one to the collection, does it instantly fire the event and cause unnecessary overhead? If so, can I somehow temporarily disable the event notifications and manually fire it once at the end of my code so that if I add 10k items, it gets only fired once, rather than 10k times?

Update: I tried having this class:

using System;
using System.Linq;
using System.Collections.Specialized;
using System.Collections.Generic;

namespace MyProject
{

    /// <summary> 
    /// Represents a dynamic data collection that provides notifications when items get added, removed, or when the whole list is refreshed. 
    /// </summary> 
    /// <typeparam name="T"></typeparam> 
    public class ObservableCollection<T> : System.Collections.ObjectModel.ObservableCollection<T>
    {

        /// <summary> 
        /// Adds the elements of the specified collection to the end of the ObservableCollection(Of T). 
        /// </summary> 
        public void AddRange(IEnumerable<T> collection)
        {
            foreach (var i in collection) Items.Add(i);
            OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, collection.ToList()));
        }

        /// <summary> 
        /// Removes the first occurence of each item in the specified collection from ObservableCollection(Of T). 
        /// </summary> 
        public void RemoveRange(IEnumerable<T> collection)
        {
            foreach (var i in collection) Items.Remove(i);
            OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, collection.ToList()));
        }

        /// <summary> 
        /// Clears the current collection and replaces it with the specified item. 
        /// </summary> 
        public void Replace(T item)
        {
            ReplaceRange(new T[] { item });
        }
        /// <summary> 
        /// Clears the current collection and replaces it with the specified collection. 
        /// </summary> 
        public void ReplaceRange(IEnumerable<T> collection)
        {
            List<T> old = new List<T>(Items);
            Items.Clear();
            foreach (var i in collection) Items.Add(i);
            OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Replace, collection.ToList()));
        }

        /// <summary> 
        /// Initializes a new instance of the System.Collections.ObjectModel.ObservableCollection(Of T) class. 
        /// </summary> 
        public ObservableCollection() : base() { }

        /// <summary> 
        /// Initializes a new instance of the System.Collections.ObjectModel.ObservableCollection(Of T) class that contains elements copied from the specified collection. 
        /// </summary> 
        /// <param name="collection">collection: The collection from which the elements are copied.</param> 
        /// <exception cref="System.ArgumentNullException">The collection parameter cannot be null.</exception> 
        public ObservableCollection(IEnumerable<T> collection) : base(collection) { }
    }
}

I get this error now:

Additional information: Range actions are not supported.

The error comes here:

OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, collection.ToList()));

解决方案

A very quick and easy way is to subclass ObservableCollection and suspend notifications when AddRange is called. See the following blog post for clarification.

这篇关于我可以暂时禁用WPF数据绑定更改吗？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！