Linq query not returning anything (Syntax might be wrong)

Question

I am trying to ensure that only NOT null items are displayed in the Console.

My code is:

internal static void RenderViews(List<BusinessProcessFlow> businessProcessListRaw)
{
    foreach (var results in businessProcessListRaw.Where(p => p.Index == 1))
    {
        var value = businessProcessListRaw.Where(x => results.EntityStep != null);
        Console.WriteLine(value);
    }

    Console.ReadLine();
}

The result is an empty console screen.

Answer 1

You should first provide model definitions BusinessProcessFlowfor class for a complete answer. If we assume that your model is something like this

public class BusinessProcessFlow
{
   public int Id {get; set;}
   public string Name { get; set; }
   public int Index { get; set; }
   public EntityStep EntityStep { get; set }

   public override string ToString() 
   { 
      return $"{Id} {Name}";
   }
}

And you want to filter all BusinessProcessFlow with Index equal to 1 and EntityStep not null , I think the query should be something like this

internal static void RenderViews(List<BusinessProcessFlow> businessProcessListRaw)
    {
        foreach (var result in businessProcessListRaw.Where(p => p.Index == 1 && p.EntityStep != null))
        {
                Console.WriteLine(result);
        }

        Console.ReadLine();
    }

Also, the type of result should have a ToString() method override in order for the console to print the data in the format you want.

Answer 2

What you are currently doing is effectively iterating over the same list two times, but with different rules; the first time, you're getting each item where Index == 1 . The next time, you're getting items where EntityStep != null . These two are not done together however, so you're likely to get a wrong answer.

You should be able to do all of that simpler using a slightly modified linq query:

internal static void RenderViews(List<BusinessProcessFlow> businessProcessListRaw)
{

    var value = businessProcessListRaw
                   .Where(p => p.Index == 1 && p.EntityStep != null)
                   .ForEach(p => Console.WriteLine(p));

    Console.ReadLine();
}

Answer 3

I'm afraid your main mistake is in this line:

var value = businessProcessListRaw.Where(x => results.EntityStep != null);

But if you say that nothing is output to the console, then most likely there is no such data in the passed collection.

You can see it here:

class Program
    {
        static void Main(string[] args)
        {
            var businessProcessListRaw = Init();

            foreach (var results in businessProcessListRaw.Where(p => p.Index == 1))
            {
                var value = businessProcessListRaw.Where(x => results.EntityStep != null);
                Console.WriteLine(value);
            }

            Console.ReadLine();
        }

        private static List<BusinessProcessFlow> Init()
        {
            return new List<BusinessProcessFlow>
            {
                new BusinessProcessFlow{Index = 1, EntityStep = new EntityStep()},
                new BusinessProcessFlow{Index = 1, EntityStep = new EntityStep()},
                new BusinessProcessFlow{Index = 2, EntityStep = new EntityStep()},
                new BusinessProcessFlow{Index = 1},
                new BusinessProcessFlow{Index = 1},
            };
        }
    }

    public class BusinessProcessFlow
    {
        public int Index { get; set; }
        public EntityStep EntityStep { get; set; }
    }

    public class EntityStep
    {
    }

The output to the console (wrong one):

And yes, as you have already been answered, just change the condition in the Where section

p => p.Index == 1 && p.EntityStep != null

Then your method will look like this:

internal static void RenderViews(List<BusinessProcessFlow> businessProcessListRaw)
{
    foreach (var results in businessProcessListRaw.Where(p => p.Index == 1 && p.EntityStep != null))
    {                
        Console.WriteLine(results);
    }

    Console.ReadLine();
}

And output to the console:

Good luck!)

Answer 4

If your mission is

to ensure that only NOT null items are displayed in the Console.

then the following would do the job.

internal static void PrintNotNulls(List<BusinessProcessFlow> businessProcessListRaw)
{
    foreach( var x in businessProcessListRaw)
    {  
       if (x != null) Console.WriteLine(x);
    }
} 

If you wish to use LINQ (the .Where bit) then the following should work.

internal static void PrintNotNulls(List<BusinessProcessFlow> businessProcessListRaw)
{
    var notNulls = businessProcessListRaw
        .Where( x => x != null);

    foreach( var x in notNulls ) 
       Console.WriteLine(x);
}

You can modify both approaches to check for more than just null: ' x.Index == 1 ' or/and ' x.EntityStep != null '.