Distinct within a Where statement

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As the statement is now it returns all items that is filtered by the N.TypeMis but I would like to have it only returning the items with a distinct N.Lvl.

I've tried using GroupBy but couldn't figure it out.

C#

var q = ( from N in _fMissionSubList
                where N.TypeMis == mTypeMis
                select new {
                  N.ID, N.Mission_ID, N.Enabled, N.Title, N.Description, N.TypeMis,
                  N.TypeParent, N.Lvl, N.LvlOrder, N.ControlType
                } ); //Would like to add something like this .Distinct(N.Lvl);

foreach ( var n in q )
{
........
}

Posted 8-Dec-10 5:34am

Serenity1

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#realJSOP · Answer 1 · 2010-12-08T05:39:00

Solution 1

Maybe this will help:

http://blogs.msdn.com/b/charlie/archive/2006/11/19/linq-farm-group-and-distinct.aspx[^]

EDIT==================

I don't understand why this was voted 1...

Posted 8-Dec-10 5:39am

#realJSOP

Updated 9-Dec-10 3:43am

v2

Comments

wizardzz 9-Dec-10 10:28am

That seems to happen a lot around here when people are expecting a code snippet to solve the problem.

cechode · Answer 2 · 2010-12-09T08:16:00

to use Distinct as you mentioned above you have to create another class the implements IEqualityComparer<whatevertypenwas>
and then pass a new instance of that to your query. For example:

C#

class NyClassN
{
    public string TypeMis { get; set; }
    public int ID { get; set; }
    public string Mission { get; set; }
}
<br /> 
class NyClassNEqComp : IEqualityComparer<NyClassN>
{
    public bool Equals(NyClassN x, NyClassN y)
    {
        return x.Mission.Equals(y.Mission) &&  x.TypeMis.Equals(y.TypeMis);
    }<br />
    public int GetHashCode(NyClassN obj)
    {
        return string.Format("{0}{1}", obj.Mission, obj.TypeMis).GetHashCode();
    }
}<br />
class Program
{
    static void TestAg(string mTypeMis)
    {
        var q = (from N in new List<NyClassN>()
                 where N.TypeMis == mTypeMis
                 select N).Distinct (new NyClassNEqComp());

    }
}

Or implement a public class DelegateComparer : IEqualityComparer{} then add an extension:

C#

public static IEnumerable Distinct(this IEnumerable items, Func equals, Func hashCode) 
{ 
    return items.Distinct(new DelegateComparer(equals, hashCode)); 
}

and then you can call

C#

.Distinct((a, b) => a.Mission_ID== b.Mission_ID, c => c.Mission_ID.GetHashCode());