C# WPF MVVM如何在ICollectionView中组合多个过滤器

我有一个问题似乎相当简单，但我似乎有一个问题：

我有一个包含一些数据的数据网格：

            <DataGrid ItemsSource="{Binding Candidates, IsAsync=True}" 
                      AutoGenerateColumns="False" 
                      EnableColumnVirtualization="True" 
                      EnableRowVirtualization="True"
                      VirtualizingStackPanel.VirtualizationMode="Standard"
                      VirtualizingStackPanel.IsVirtualizing="True"
                      CanUserAddRows="false">

                <DataGrid.Columns>
                    <DataGridTextColumn Binding="{Binding Firstname}" Header="Imię" />
                    <DataGridTextColumn Binding="{Binding Lastname}" Header="Nazwisko" />
                    <DataGridTextColumn Binding="{Binding commendation.Name}" Header="Polecenie" />
  </DataGrid.Columns>
</DataGrid>

过滤器看起来像：

    public void FilterFirstname(object obj)
    {
        this.Candidates.Filter += item =>
        {
            Candidate candidate = item as Candidate;
            return candidate.Firstname.Contains(obj.ToString());
        };

        this.Candidates.Refresh();
    }

    public void FilterLastname(object obj)
    {
        this.Candidates.Filter += item =>
        {
            Candidate candidate = item as Candidate;

            if(string.IsNullOrWhiteSpace(candidate.Lastname))
            {
                return false;
            }

            return candidate.Lastname.Contains(obj.ToString());
        };

        this.Candidates.Refresh();
    }

    public void FilterCommendation(object obj)
    {
        this.Candidates.Filter += item =>
        {
            Candidate candidate = item as Candidate;

            if (string.IsNullOrWhiteSpace(candidate.commendation.Name))
            {
                return false;
            }

            return candidate.commendation.Name.Contains(obj.ToString());
        };

        this.Candidates.Refresh();
    }

现在，这基本上是按预期工作，但它在每个列上分别工作，因此，如果我键入name，它将筛选我的姓名，如果我键入last name，它将筛选我的last name，但它将覆盖name，因此我不会得到name和last name的精确匹配，我希望聚合这些筛选器

---

有什么方法可以聚合这些过滤器吗

为什么它不起作用？

在每个

filterCommandation

，

FilterLastname

，

FilterFirstname

上，您正在向

此.Candidates.Filter添加另一个代理。它们都将在刷新时执行，但只返回最后一次委托的结果。考虑下面的例子：

Predicate<int> tmp = i => true;
tmp += i => i != 0;

Assert.AreEqual(true, tmp(1));
Assert.AreEqual(false, tmp(0));

filters属性是什么样子的？我刚刚添加了
filters
字段的定义。要将其用于“或”过滤器，我在FilterCandidates的聚合方法中更改了“&&”到“||”，将“true”改为“false”。在聚合之前还必须添加一行：filters.count==0->returntrue
Predicate<int> tmp = i => true;
tmp += i => i != 0;

Assert.AreEqual(true, tmp(1));
Assert.AreEqual(false, tmp(0));

    Dictionary<string, Predicate<Candidate>> filters
        = new Dictionary<string, Predicate<Candidate>>();

    public CatalogViewModel()
    {
        ...

        Candidates.Filter = FilterCandidates;
    }

    private bool FilterCandidates(object obj)
    {
        Candidate c = (Candidate)obj;
        return filters.Values
            .Aggregate(true,
                (prevValue, predicate) => prevValue && predicate(c));
    }
    public void FilterFirstname(object obj)
    {
        string val = obj.ToString();
        AddFilterAndRefresh(
            "FirstName",
            candidate => candidate.Firstname.Contains(val));
    }

    public void FilterLastname(object obj)
    {
        string val = obj.ToString();
        AddFilterAndRefresh(
            "FirstName",
            candidate => !string.IsNullOrWhiteSpace(candidate.Lastname) && candidate.Lastname.Contains(val));
    }

    public void ClearFilters()
    {
        filters.Clear();
        Candidates.Refresh();
    }

    public void RemoveFilter(string filterName)
    {
        if (filters.Remove(filterName))
        {
            Candidates.Refresh();
        }
    }

    private void AddFilterAndRefresh(string name, Predicate<Candidate> predicate)
    {
        filters.Add(name, predicate);
        Candidates.Refresh();
    }