Solved

Help with LINQ order by query syntax

Posted on 2014-10-14
10
127 Views
Last Modified: 2016-02-15
Hi, the following code works fine

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

namespace ConsoleApplication198
{
    class Test
    {
        public String Name { get; set; }
        public int ID { get; set; }
    }

    class Program
    {
        public void Start()
        {
            Test t1 = new Test{Name = "Fred", ID = 123 };
            Test t2 = new Test { Name = "John", ID = 4 };
            List<Test> t = new List<Test> { t1, t2 };

            var p = (new String[] { "All Employees" }).Union(from x
                                                                in t
                                                                orderby x.Name ascending
                                                                  select x.Name                                                                 
                                                            ).ToList<String>();
            //p is a List<String> that I can assign to a dropdownList.DataSource
            //and "All Employees" appears at the top, most of the time
        }

        static void Main(string[] args)
        {
            Program p = new Program();
            p.Start();
        }
    }
}

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It works.
"p" is used as a DataSource for a DropDownList
All of the time in this test program things always work.
Most but not all the time it works in a more complex program. The problem I am seeing is that "All Employees" in my real application only sometimes appears at the top of the list. I always need it at the top of the list in my drop down.

Can someone help how I can "order by" to ensure that "p" is always a list where p[0]="All Employees".

Thank you
0
Comment
Question by:John Bolter
  • 4
  • 3
  • 2
10 Comments
 
LVL 63

Accepted Solution

by:
Fernando Soto earned 250 total points
ID: 40380116
Hi John;

I have removed the method call to Union and placed an Insert method call to insert  "All Employees" at the beginning of the List.

var p = (from x in t
         orderby x.Name ascending
         select x.Name
         ).ToList<String>();

// Insert this value at the begining of the list.
p.Insert(0, "All Employees");

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0
 
LVL 33

Assisted Solution

by:it_saige
it_saige earned 250 total points
ID: 40380273
I agree with Fernando.

You either insert the "All Employees" item to the list at the 0 position:
using System;
using System.Collections.Generic;
using System.Linq;

namespace ConsoleApplication198
{
	class Test
	{
		public String Name { get; set; }
		public int ID { get; set; }
	}

	class Program
	{
		public void Start()
		{
			Test t1 = new Test { Name = "Fred", ID = 123 };
			Test t2 = new Test { Name = "John", ID = 4 };
			List<Test> t = new List<Test> { t1, t2 };
			List<String> p = new List<String>();

			p = (from x in t
				orderby x.Name ascending
				select x.Name).ToList();
			//p is a List<String> that I can assign to a dropdownList.DataSource
			//and "All Employees" appears at the top, most of the time

			p.Insert(0, "All Employees");

			foreach (var employee in p)
				Console.WriteLine(employee);
			Console.ReadLine();
		}

		static void Main(string[] args)
		{
			Program p = new Program();
			p.Start();
		}
	}
}

Open in new window

Output:Capture.JPGOr create the list with the first item specified as "All Employees" and then use List.AddRange(IEnumerable<String>) to add your remaining elements:
using System;
using System.Collections.Generic;
using System.Linq;

namespace ConsoleApplication198
{
	class Test
	{
		public String Name { get; set; }
		public int ID { get; set; }
	}

	class Program
	{
		public void Start()
		{
			Test t1 = new Test { Name = "Fred", ID = 123 };
			Test t2 = new Test { Name = "John", ID = 4 };
			List<Test> t = new List<Test> { t1, t2 };
			List<String> p = new List<String>() { "All Employees" };
			p.AddRange(from x in t
					 orderby x.Name ascending
					 select x.Name);
			//p is a List<String> that I can assign to a dropdownList.DataSource
			//and "All Employees" appears at the top, most of the time

			foreach (var employee in p)
				Console.WriteLine(employee);
			Console.ReadLine();
		}

		static void Main(string[] args)
		{
			Program p = new Program();
			p.Start();
		}
	}
}

Open in new window

Output:Capture.JPG
-saige-
0
 

Author Comment

by:John Bolter
ID: 40380285
I was so close.
Thank you both
0
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LVL 33

Expert Comment

by:it_saige
ID: 40380291
@John, while I appreciate the points.  I really think that Fernando deserves credit also.

-saige-
0
 

Author Comment

by:John Bolter
ID: 40380297
I tried to split it 50:50 but I couldn't figure out how. And now I can't seem to undo it. I thought it too.
0
 
LVL 33

Expert Comment

by:it_saige
ID: 40380302
We can have an administrator reopen so that you can re-assign the points accordingly.

-saige-
0
 
LVL 33

Expert Comment

by:it_saige
ID: 40380304
I have sent an attention request.

-saige-
0
 

Author Comment

by:John Bolter
ID: 40380318
Thanks & sorry about this guys, 50/50, it was my error.
I can't see to write LINQ or use this website :-(
0
 
LVL 63

Expert Comment

by:Fernando Soto
ID: 40380553
Thank you -saige- and John for your efforts.
0

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