Where condition inside lambda expression c#

Question

I have a entity like

public class Program
{    
    public int ID { get; set; }
    public bool IsActive { get; set; } 
    public string Title { get; set; }
}

and

public class EMetrics
{
    public int ID { get; set; }
    public bool IsActive { get; set; }
    public string Title { get; set; }
    public List<Program> Programs { get; set; }
}

I have repository method like,

IEnumerable<EMetrics> IEmetricsRepository.GetAllByProgram(params int[] programIds)
{
    var metrics = EntitySet
        .Where(x => programIds.Contains(x.Programs.Select(x => x.ID)))
        .ToList();

        return metrics;
}

[The above code throwing build error]

Here only where I am facing problem to get the EMetrics based on the program Ids array params.

I want list Emetrics which are associated with the program.

Answer 1

You're incorrectly accessing the same input parameter in your LINQ. It should be refactored by changing your inner Select to use a different parameter:

IEnumerable<EMetrics> IEmetricsRepository.GetAllByProgram(params int[] programIds)
{
    var metrics = EntitySet
        .Where(x => programIds.Contains(x.Programs.Select(y => y.ID)))
        .ToList();

    return metrics;
}

Answer 2

So you want to check if all elements of one collection are present in the other. In LINQ that can be done with combination of Except and Any:

var metrics = EntitySet
    .Where(x => x.Programs.Select(p => p.ID).Except(programIds).Any())
    .ToList();

Fyi - your current code is failing because Array.Contains expects a single item, an int in this case, while you are giving it a whole enumerable