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How Do I filter Generic List<> with Object of same Class

Answer 1

+1 A:

I would not filter where you are filtering. I would pass the filter to the load of the collection and use it internally there, either by passing those criteria to the service or the database or similar, or by forcing each object to validate itself against the criteria before adding it to the collection.

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;
    }
}

Cade Roux 2009-06-08 17:17:56

Answer 2

A:

How are you filtering? Are you excluding contracts deserialized from json? Are you having an issue with evaluating equality? Its a little hard to get the issue here.

Filtering one list with another is pretty easy with Linq:

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;

This results in result containing 2, 4. You just have to have an Equals method in your data contract that performs whatever equivalency tests your requirements dictate.

If your UI allows users to "create" 1 to n contracts to filter on, and you get this as a collection of contracts (none to all of which may be null), this will still work.

In response to Zacho's comment:

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;

The filter enumerable--bar--contains nulls. This function works. If this solution doesn't work for you, Zacho, you've got a different issue. My guess it would have something to do with equality comparisons.

Will 2009-06-08 17:21:29

I like the idea, but this does not work because some of the members of the filters may be null, so using the above example filters nothing.

Zacho 2009-06-08 17:38:38

Good observation Will. Your right in that your sample works, it worked for me too, but using that exact same idea, and plugging in the appropriate values for my use, and the filter does not work. Here is what I am doing. var resultx = from x in contracts where !filters.Contains(x) select x;

Zacho 2009-06-08 17:57:34

You need to implement Equals in your objects. Contains is using the default implementation of Equals(on System.Object), which is a reference check. You want an implementation of Equals that checks properties within the object for equality. If that's not understandable, I suggest you grab CLR Via C# and read it.

Will 2009-06-08 20:17:09

From my answer: "You just have to have an Equals method in your data contract that performs whatever equivalency tests your requirements dictate." http://msdn.microsoft.com/en-us/library/bsc2ak47.aspx

Will 2009-06-08 20:18:24

Thanks Will. As much as I hate to do this, I have to give up. I will have to build a manual json object and filter the list manually. The solution really sucks, but this is too far above my head and staring at it for several days doesn't help.

Zacho 2009-06-08 20:39:25

Answer 3

A:

Send the items of both collections to XElements, making each property an XAttribute.

Then you can compare attributes to find matches, which is easy.

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;
    }
}

Then to compare them....

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);

Also:

If you send in one empty example (all defaults), you get back the whole source list.
If you send in no examples (an empty list), you get back nothing.

David B 2009-06-08 18:23:18

Do you have an example?

Zacho 2009-06-08 18:24:49

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How Do I filter Generic List<> with Object of same Class

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