我想在一个包含6列的DataGrid中使用max 3000项过滤ObservableCollection。用户应该能够以“&&”方式过滤所有6列。
我应该使用LINQ还是CollectionView？ LINQ似乎更快尝试一些www样本。你有任何赞成/缺点吗？
更新：
private ObservableCollection<Material> _materialList;
private ObservableCollection<Material> _materialListInternal;
public MaterialBrowserListViewModel()
{
_materialListInternal = new ObservableCollection<Material>();
for (int i = 0; i < 2222; i++)
{
var mat = new Material()
{
Schoolday = DateTime.Now.Date,
Period = i,
DocumentName = "Excel Sheet" + i,
Keywords = "financial budget report",
SchoolclassCode = "1",
};
_materialListInternal.Add(mat);
var mat1 = new Material()
{
Schoolday = DateTime.Now.Date,
Period = i,
DocumentName = "Word Doc" + i,
Keywords = "Economical staticstics report",
SchoolclassCode = "2",
};
_materialListInternal.Add(mat1);
}
MaterialList = CollectionViewSource.GetDefaultView(MaterialListInternal);
MaterialList.Filter = new Predicate<object>(ContainsInFilter);
}
public bool ContainsInFilter(object item)
{
if (String.IsNullOrEmpty(FilterKeywords))
return true;
Material material = item as Material;
if (DocumentHelper.ContainsCaseInsensitive(material.Keywords,FilterKeywords,StringComparison.CurrentCultureIgnoreCase))
return true;
else
return false;
}
private string _filterKeywords;
public string FilterKeywords
{
get { return _filterKeywords; }
set
{
if (_filterKeywords == value)
return;
_filterKeywords = value;
this.RaisePropertyChanged("FilterKeywords");
MaterialList.Refresh();
}
}
public ICollectionView MaterialList { get; set; }
public ObservableCollection<Material> MaterialListInternal
{
get { return _materialListInternal; }
set
{
_materialListInternal = value;
this.RaisePropertyChanged("MaterialList");
}
}
对于交互式（DataGrid？）体验，您应该使用Collection View。对于更加面向代码的排序，LINQ。
对于最多3000项，速度不应该是UI中的（主要）因素。
两者怎么样？ Thomas Levesque围绕ICollectionView构建了一个支持LINQ的包装器。
用法：
IEnumerable<Person> people;
// Using query comprehension
var query =
from p in people.ShapeView()
where p.Age >= 18
orderby p.LastName, p.FirstName
group p by p.Country;
query.Apply();
// Using extension methods
people.ShapeView()
.Where(p => p.Age >= 18)
.OrderBy(p => p.LastName)
.ThenBy(p => p.FirstName)
.Apply();
码：
public static class CollectionViewShaper
{
public static CollectionViewShaper<TSource> ShapeView<TSource>(this IEnumerable<TSource> source)
{
var view = CollectionViewSource.GetDefaultView(source);
return new CollectionViewShaper<TSource>(view);
}
public static CollectionViewShaper<TSource> Shape<TSource>(this ICollectionView view)
{
return new CollectionViewShaper<TSource>(view);
}
}
public class CollectionViewShaper<TSource>
{
private readonly ICollectionView _view;
private Predicate<object> _filter;
private readonly List<SortDescription> _sortDescriptions = new List<SortDescription>();
private readonly List<GroupDescription> _groupDescriptions = new List<GroupDescription>();
public CollectionViewShaper(ICollectionView view)
{
if (view == null)
throw new ArgumentNullException("view");
_view = view;
_filter = view.Filter;
_sortDescriptions = view.SortDescriptions.ToList();
_groupDescriptions = view.GroupDescriptions.ToList();
}
public void Apply()
{
using (_view.DeferRefresh())
{
_view.Filter = _filter;
_view.SortDescriptions.Clear();
foreach (var s in _sortDescriptions)
{
_view.SortDescriptions.Add(s);
}
_view.GroupDescriptions.Clear();
foreach (var g in _groupDescriptions)
{
_view.GroupDescriptions.Add(g);
}
}
}
public CollectionViewShaper<TSource> ClearGrouping()
{
_groupDescriptions.Clear();
return this;
}
public CollectionViewShaper<TSource> ClearSort()
{
_sortDescriptions.Clear();
return this;
}
public CollectionViewShaper<TSource> ClearFilter()
{
_filter = null;
return this;
}
public CollectionViewShaper<TSource> ClearAll()
{
_filter = null;
_sortDescriptions.Clear();
_groupDescriptions.Clear();
return this;
}
public CollectionViewShaper<TSource> Where(Func<TSource, bool> predicate)
{
_filter = o => predicate((TSource)o);
return this;
}
public CollectionViewShaper<TSource> OrderBy<TKey>(Expression<Func<TSource, TKey>> keySelector)
{
return OrderBy(keySelector, true, ListSortDirection.Ascending);
}
public CollectionViewShaper<TSource> OrderByDescending<TKey>(Expression<Func<TSource, TKey>> keySelector)
{
return OrderBy(keySelector, true, ListSortDirection.Descending);
}
public CollectionViewShaper<TSource> ThenBy<TKey>(Expression<Func<TSource, TKey>> keySelector)
{
return OrderBy(keySelector, false, ListSortDirection.Ascending);
}
public CollectionViewShaper<TSource> ThenByDescending<TKey>(Expression<Func<TSource, TKey>> keySelector)
{
return OrderBy(keySelector, false, ListSortDirection.Descending);
}
private CollectionViewShaper<TSource> OrderBy<TKey>(Expression<Func<TSource, TKey>> keySelector, bool clear, ListSortDirection direction)
{
string path = GetPropertyPath(keySelector.Body);
if (clear)
_sortDescriptions.Clear();
_sortDescriptions.Add(new SortDescription(path, direction));
return this;
}
public CollectionViewShaper<TSource> GroupBy<TKey>(Expression<Func<TSource, TKey>> keySelector)
{
string path = GetPropertyPath(keySelector.Body);
_groupDescriptions.Add(new PropertyGroupDescription(path));
return this;
}
private static string GetPropertyPath(Expression expression)
{
var names = new Stack<string>();
var expr = expression;
while (expr != null && !(expr is ParameterExpression) && !(expr is ConstantExpression))
{
var memberExpr = expr as MemberExpression;
if (memberExpr == null)
throw new ArgumentException("The selector body must contain only property or field access expressions");
names.Push(memberExpr.Member.Name);
expr = memberExpr.Expression;
}
return String.Join(".", names.ToArray());
}
}
图片来源：http://www.thomaslevesque.com/2011/11/30/wpf-using-linq-to-shape-data-in-a-collectionview/
基于视觉复杂性和项目数量，确实会有明显的性能差异，因为Refresh方法重新创建了整个视图！