如何使用同一类的对象过滤泛型列表

我不会过滤你过滤的地方。我将把过滤器传递给集合的负载,并在那里内部使用它,方法是将这些条件传递给服务、数据库或类似的对象,或者在将每个对象添加到集合之前,强制每个对象根据这些条件验证自己。

public List<StaffingPositionsDataContract> GetStaffingPosition(string searchFilters)
{
    var filters = JsonConvert.DeserializeObject<List<StaffingPositionsDataContract>>(searchFilters);
    IList<StaffingPositionsDataContract> contracts = new StaffingPositionsDataContract().LoadMockData(searchFilters);

    return contracts;
}

[DataContract] [Serializable]
public class StaffingPositionsDataContract
{
    [DataMember(Order = 1)] public int PositionId { get; set; }
    [DataMember(Order = 2)] public string Series { get; set; }
    [DataMember(Order = 3)] public string BFY { get; set; }
    [DataMember(Order = 4)] public string BudgetStatus { get; set; }
    [DataMember(Order = 5)] public string DutyStation { get; set; }
    [DataMember(Order = 6)] public string OrgLocation { get; set; }
    [DataMember(Order = 7)] public string BudgetingEntity { get; set; }
    [DataMember(Order = 8)] public string SeriesTitle { get; set; }
    [DataMember(Order = 9)] public int PersonnelId { get; set; }
    [DataMember(Order = 10)] public string PositionStatus { get; set; }
    [DataMember] public int RecId { get; set; }

    public List<StaffingPositionsDataContract> LoadMockData(string searchfilters)
    {
        // filter the list returned here

        List<StaffingPositionsDataContract> staffingposition = new List<StaffingPositionsDataContract>()
        {
            new StaffingPositionsDataContract() {RecId=1, PositionId = 12345, Series="", BFY="FY2010", BudgetStatus="Actual", DutyStation="", OrgLocation="", BudgetingEntity=""},
            new StaffingPositionsDataContract() {RecId=2, PositionId = 67891, Series="", BFY="FY2011", BudgetStatus="Actual", DutyStation="", OrgLocation="", BudgetingEntity=""},
            new StaffingPositionsDataContract() {RecId=3,PositionId = 12345, Series="", BFY="FY2010", BudgetStatus="Projected", DutyStation="", OrgLocation="", BudgetingEntity=""},
            new StaffingPositionsDataContract() {RecId=4,PositionId = 67892, Series="", BFY="FY2011", BudgetStatus="Projected", DutyStation="", OrgLocation="", BudgetingEntity=""},
            new StaffingPositionsDataContract() {RecId=5,PositionId = 987654, Series="", BFY="FY2010", BudgetStatus="Projected", DutyStation="", OrgLocation="", BudgetingEntity=""}
        };
        return staffingposition;
    }
}

然后您可以比较属性以找到匹配项,这很容易。

public class Customer
{
    public int CustomerId { get; set; }
    public string Name { get; set; }
    public string FavoriteColor { get; set; }

    // probably a better way to do this
    // just writing fast for demo
    public XElement ToXElement()
    {
        List<XAttribute> attributes = new List<XAttribute>();

        if (this.CustomerId != 0)
            attributes.Add(new XAttribute("CustomerId", this.CustomerId));
        if (this.Name != null)
            attributes.Add(new XAttribute("Name", this.Name));
        if (this.FavoriteColor != null)
            attributes.Add(new XAttribute("FavoriteColor", this.FavoriteColor));

        XElement result = new XElement("Customer", attributes);
        return result;
    }
}

List<Customer> source = new List<Customer>()
{ new Customer(){ CustomerId=1, FavoriteColor="Blue", Name="Alex" },
  new Customer(){ CustomerId=2, FavoriteColor="Green", Name="Bob" },
  new Customer(){ CustomerId=3, FavoriteColor="Blue", Name="Cindy" },
  new Customer(){ CustomerId=4, FavoriteColor="Red", Name="Darren" }
};
List<Customer> examples = new List<Customer>()
{ new Customer(){ FavoriteColor="Blue", CustomerId = 3},
  new Customer(){ Name="Darren"}
};

List<XElement> sourceElements = source.Select(c => c.ToXElement()).ToList();
List<XElement> exampleElements = examples.Select(c => c.ToXElement()).ToList();

//and now the query...
var query = sourceElements
  .Where(s => exampleElements
    .Any(ex => ex.Attributes()
      .All(exatt => s.Attribute(exatt.Name).Value == exatt.Value)
    )
  );

foreach(XElement x in query)
  Console.WriteLine(x);

也:

• 如果您发送一个空示例(所有默认值),那么您将返回整个源代码列表。
• 如果你没有发送任何示例(一个空列表),你什么也得不到。

使用Linq,用一个列表过滤另一个列表非常简单:

var foo = new int[]{1,2,3,4,5};
var bar = new int[]{1,3,5};
var result = from x in foo where !bar.Contains(x) select x;

您只需要在数据契约中有一个Equals方法,它执行您的需求所要求的任何等价性测试。

如果您的UI允许用户“创建”1到n个要筛选的契约,并且您将其作为契约的集合(无到所有的契约都可能为空),那么这仍然有效。

针对扎乔的评论:

var foo = new string[]{"1","2","3","4","5"}; 
var bar = new string[]{"1","3",null,"5"};
var result = from x in foo where !bar.Contains(x) select x;

筛选器可枚举项bar包含空值。此功能有效。如果这个解决方案对你不起作用,扎乔,你就有另一个问题了。我猜这和平等比较有关。