Except Confusion

Lost User

I will keep things simple first. If I have 2 Lists of ints say ds1 and ds2 and in ds1 I put {1,1,2} and in ds2 I put {2} and then I use var except = ds1.Except(ds2) , except will contain only {1}. This I understand. However, if I make Lists of points say dsp1 and dsp 2 and in dsp1 I put {(1,2),(3,4)} and in dsp2 I put {(3,4),(5,6)} and then I use var except = dsp1.Except(dsp2) , except will contain all of them... i.e. {(1,2),(3,4),(5,6)} This behavior boggles my mind. Maybe I am missing something simple here. Either way when I use custom containers, i.e. List and my IEquatable object overrides GetHashCode and I have built my Equals properly, I am seeing behavior that resembles the opposite of what I posted for the integers. i.e. both '10' would get returned. Anyone have any idea??

"9 Pregnent woman can not have a baby in 1 month" -Uknown

Lost User

More Info: Made a custom Point object "MyPoint" that inherits from IQuatable.. Here it is...

class MyPoint : IEquatable
{
    public int? X { get; set; }
    public int? Y { get; set; }

    #region IEquatable Members

    public bool Equals(MyPoint other)
    {
        // Check whether the compared object is null.
        if (Object.ReferenceEquals(other, null)) return false;

        // Check whether the compared object references the same data.
        if (Object.ReferenceEquals(this, other)) return true;

        bool match = false;
        bool compared = false;

        MyPoint oPoint = other as MyPoint;

        if (X.HasValue && oPoint.X.HasValue)
        {
            compared = true;
            match = X.Value.Equals(X.Value);
        }

        if (match && Y.HasValue && oPoint.Y.HasValue)
        {
            compared = true;
            match = Y.Value.Equals(oPoint.Y.Value);
        }

        return match && compared;
        
    }

    public override int GetHashCode()
    {
        int hash = 17;
        hash = X.HasValue ? (hash \* 23) + X.Value.GetHashCode() : (hash \* 23) + 1;
        hash = Y.HasValue ? (hash \* 23) + Y.Value.GetHashCode() : (hash \* 23) + 2;
        return hash;
    }

    #endregion
}

So in the dsp1 and dsp2 I changed them to be List and ran as set. This resulted in the following, {(1,2,(3,4),(3,4),(5,6)} Seriously?? :wtf: Modded- Has a typo in the Equals... It was changed to the above and now the same output is generated. i.e {(1,2,(3,4),(5,6)} So Why the heck am I getting (5,6) in this data set?

"9 Pregnent woman can not have a baby in 1 month" -Uknown

modified on Wednesday, September 30, 2009 4:08 PM

Gideon Engelberth · modified on Wednesday, September 30, 2009 4:08 PM

I am using your class and do not see the results you are getting (I am getting just [1,2]). Could you put up more code to show where you are declaring and filling ds1 and ds2. (Maybe even a complete little console app to show the output.)

Lost User

Sure can.. Here it is:

class Program
{
static List dsp1 = new List();
static List dsp2 = new List();

    static void Main(string\[\] args)
    {
        FillDataPoints1();
        FillDataPoints2();

        var except = dsp1.Except(dsp2);

        StringBuilder sb = new StringBuilder();
        sb.Append("{");
        foreach (var item in except)
        {
            sb.Append("(" + item.X.ToString() + ", " + item.Y.ToString() + "), ");
        }
        string output = sb.ToString().Substring(0, sb.ToString().Length - 2) + "}";
        Console.WriteLine(output);
        Console.WriteLine("Press ANy Key To Continue...");
        Console.Read();
    }

    static private void FillDataPoints1()
    {
        dsp1.Add(new MyPoint()
        {
            X = 1,
            Y = 2
        });

        dsp1.Add(new MyPoint()
        {
            X = 3,
            Y = 4
        });
    }

    static private void FillDataPoints2()
    {
        dsp1.Add(new MyPoint()
        {
            X = 3,
            Y = 4
        });

        dsp1.Add(new MyPoint()
        {
            X = 5,
            Y = 6
        });
    }
}

The MyPoint is that from above.

"9 Pregnent woman can not have a baby in 1 month" -Uknown

Lost User

Oops. My second one is not filled. THat is why my test code is not working... Ok well that works. Now I just need my more complicated one to work. Back to the drawing board. Thanks for your help though :)

"9 Pregnent woman can not have a baby in 1 month" -Uknown

bhogsett

I am new to vb.net and LINQ. I do not understand what you understand when you said: "If I have 2 Lists of ints say ds1 and ds2 and in ds1 I put {1,1,2} and in ds2 I put {2} and then I use var except = ds1.Except(ds2) , except will contain only {1}. This I understand." I expected except to contain {1,1}. Please explain. What I am trying to do is this. Read a text file, exclude a group of words from the file and then use regex and linq to choose the words (maybe all words longer than 6 letters) count number of uses of a word and to group and order the output. Everything is working fine except the exclusion of words. I thought Except was the answer, but was very surprised to see that it removed duplicates from the target string. Any suggestions will be appreciated. Bill:confused: