How to get minimum from multiple date columns in linq?

Question

I have 3 date type column in a table and i want to get only one minimum date from all the columns using linq.

Table: Collected Staged Processed
1/20/2017 2/19/2017 3/17/2016
4/21/2017 6/18/2014 12/15/2015

Needed result: 6/18/2014

Currently i am using following code:

var collectedDate = queryResults.Min(d => d.Collected);
var stagedDate = queryResults.Min(d => d.Staged);
var ProcessedDate = queryResults.Min(d => d.Processed);

And then comparing these all three and store the minimum date in another variable. How can i do it in some other good way?

Answer 1

As you working with database, it will be better to make one query instead of three:

var answer = (from item in queryResults
              group item by 0 into sub
              select new
              {
                  min1 = sub.Min(x => x.Collected),
                  min2 = sub.Min(x => x.Staged),
                  min3 = sub.Min(x => x.Processed)
              }).ToList().Select(x => new[] { x.min1, x.min2, x.min3 }.Min()).FirstOrDefault();

Answer 2

You have to create List using collectedDate,stagedDate,ProcessedDate then apply Linq on it. Please check this.

Code:

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

public class Program
{
    public class Test
    {
        public DateTime Collected {get; set;}
        public DateTime Staged {get; set;}
        public DateTime Processed {get; set;}
    }

    public static void Main()
    {
        List<Test> queryResults = new List<Test>();

        queryResults.Add(new Test(){Collected=Convert.ToDateTime("1/20/2017"),Staged=Convert.ToDateTime("2/19/2017"),Processed=Convert.ToDateTime("3/17/2016")});
        queryResults.Add(new Test(){Collected=Convert.ToDateTime("4/21/2017"),Staged=Convert.ToDateTime("6/18/2014"),Processed=Convert.ToDateTime("12/15/2015")});

        var collectedDate = queryResults.Min(d => d.Collected);
        var stagedDate = queryResults.Min(d => d.Staged);
        var ProcessedDate = queryResults.Min(d => d.Processed);

        List<DateTime> listDate = new List<DateTime>(){collectedDate,stagedDate,ProcessedDate};

        Console.WriteLine(listDate.Min(d => d));

        //2nd Solution
        //Compare DateTime between column and then rows to get min value
        Console.WriteLine(queryResults.Min(d => getMin(getMin(d.Collected, d.Staged), d.Processed)));
    }

    //Function to compare two DateTime
    public static DateTime getMin(DateTime a, DateTime b)
    {
        return a < b ? a : b;
    }
}

You can check output of the code in DotNetFiddle.