find distinct element in list in C#

I have a list

   List<string[]> finalResult = new List<string[]>();

after it contains

 finalResult[0][0]='After'
 finalResult[1][0]='Before'
 finalResult[2][0]='Before'

I want to find number of distinct elements in this list. I am using

int noElements=  finalResult.Distinct<string[]>().ToList().Count;

But it is showing no开发者_如何学JAVAElements=3. Any idea why?

---

The reason you get all three is that the list contains three different string arrays. Two of them happen to have the same content, but it's still two different arrays.

A quick attempt to solve it could look like this:

First create an IEqualityComparer<string[]>:

public class StringArrayComparer : IEqualityComparer<string[]>
{

    public bool Equals(string[] x, string[] y)
    {
        if (x==y)
        {
            return true;
        }

        if (x== null || y == null)
        {
            return false;
        }

        return x.Except(y).Count() == 0;
    }

    public int GetHashCode(string[] obj)
    {
        // there may be better implementations of GetHashCode
        int sum = obj.Sum(s => s.GetHashCode());
        return sum.GetHashCode();
    }
}

...then use that comparer when calling Distinct:

var comparer = new StringArrayComparer();
int distinctCount = finalResult.Distinct(new StringArrayComparer()).Count();

---

Why do you have a 2-dimensional array here, when you only use one of the dimensions?

Your code should look like this:

 List<string> finalResult = new List<string>();

finalResult[0]="After";
finalResult[1]="Before";
finalResult[2]="Before";

Then you should get the wanted result

int noElements=  finalResult.Distinct().Count(); //returns 2

---

you need to pass in an IEqualityComparer object that instructs the distinct method on how to compare string arrays.

Define the comparer:

public class MyComparer : IEqualityComparer<string[]>
{
  public bool Equals(string[] a, string[] b)
  {
    if (a.Length != b.Length ) return false;

    for (int i  = 0; i < a.Length;i++)
    {
       if (a[i] != b[i])
         return false;
    }

    return true;
  }



 public int GetHashCode(string[] a)
  {
    return a.GetHashCode();
  }
}

call with:

finalResult.Distinct(new MyComparer()).Count();