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How to write LINQ query

Posted on 2014-12-22
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Last Modified: 2016-02-15
Hi, yet another LINQ query. My apologies I cannot get the hang of this. This should be simple. My code is below.
Thank you
John

using System;
using System.Collections.Generic;
using System.Linq;

namespace ConsoleApplication5
{
    class Program
    {
        static void Main(string[] args)
        {
            Dictionary<int, List<Single>> test = new Dictionary<int, List<Single>>();

            test.Add(1, new List<Single> { 1f, 2f, 3f, 4f });
            test.Add(15, new List<Single> { 1.1f, 2f });
            test.Add(99, new List<Single> { 1.1f, 1f, 2f });

            int totalNumberOfValues = test.Sum(n => n.Value.Count());   //returns 9 which is correct

            //the distinct values are 1f, 2f, 3f, 4f, 1.1f, counting them there are 5 values
            //I want to count them
            int totalNumberOfDistinctValue = what goes here;      //I want this to be 5
        }
    }
}

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Question by:John Bolter
  • 2
4 Comments
 
LVL 33

Accepted Solution

by:
it_saige earned 500 total points
ID: 40513104
You would use:
int totalNumberOfDistinctValue = test.SelectMany(n => n.Value).Distinct().Count();

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Example -
using System;
using System.Collections.Generic;
using System.Linq;

namespace EE_Q28585282
{
	class Program
	{
		static void Main(string[] args)
		{
			Dictionary<int, List<Single>> test = new Dictionary<int, List<Single>>();

			test.Add(1, new List<Single> { 1f, 2f, 3f, 4f });
			test.Add(15, new List<Single> { 1.1f, 2f });
			test.Add(99, new List<Single> { 1.1f, 1f, 2f });

			int totalNumberOfValues = test.Sum(n => n.Value.Count());   //returns 9 which is correct
			Console.WriteLine(string.Format("Total number of values: {0}", totalNumberOfValues));

			//the distinct values are 1f, 2f, 3f, 4f, 1.1f, counting them there are 5 values
			//I want to count them
			int totalNumberOfDistinctValue = test.SelectMany(n => n.Value).Distinct().Count();      //I want this to be 5
			Console.WriteLine(string.Format("Total number of distinct values: {0}", totalNumberOfDistinctValue));
			Console.ReadLine();
		}
	}
}

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Produces the following output -Capture.JPG
More on SelectMany - http://msdn.microsoft.com/en-us/library/system.linq.enumerable.selectmany%28v=vs.100%29.aspx

-saige-
0
 

Author Closing Comment

by:John Bolter
ID: 40513139
Oh of course.

I even wrote

test.Select(n => n.Value).Distinct().Count();

that didn't work. I wasn't even away of SelectMany.

Thank you!
0
 
LVL 85

Expert Comment

by:Mike Tomlinson
ID: 40513231
If you're interested in what those distinct values are, and how many of them there were, then:
        static void Main(string[] args)
        {
            Dictionary<int, List<Single>> test = new Dictionary<int, List<Single>>();

            test.Add(1, new List<Single> { 1f, 2f, 3f, 4f });
            test.Add(15, new List<Single> { 1.1f, 2f });
            test.Add(99, new List<Single> { 1.1f, 1f, 2f });

            int totalNumberOfValues = test.Sum(n => n.Value.Count());  

            var distinctValuesWithCount = test.SelectMany(x => x.Value) // flatten the dictionary values to a single List<Single>
                .GroupBy(x => x) // grouped by each Single in the List
                .Select(group => new // create an anonymous type with the value and number of occurrences of that Single
                {
                    Value = group.Key,
                    Count = group.Count()
                })
                .OrderBy(x => x.Value); // sorted ascending by the Single

            int totalNumberOfDistinctValue = distinctValuesWithCount.Count();

            Console.WriteLine("totalNumberOfDistinctValue = " + totalNumberOfDistinctValue.ToString());
            foreach(var g in distinctValuesWithCount)
            {
                Console.WriteLine("value = " + g.Value.ToString() + ", Count = " + g.Count.ToString());
            }
            Console.ReadLine();
        }

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Output:
totalNumberOfDistinctValue = 5
value = 1, Count = 2
value = 1.1, Count = 2
value = 2, Count = 3
value = 3, Count = 1
value = 4, Count = 1

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0
 

Author Comment

by:John Bolter
ID: 40514441
Thanks,
0

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