Question

I have another question that’s connected with my class:

public class Parent {
        public IList<ParentDetail> ParentDetails {
            get { return _ParentDetails; }
        }
        private List<ParentDetail> _ParentDetails = new List<ParentDetail>();
        public Parent() {
            this._ParentDetails = new List<ParentDetail>();
        }
    }

    public class ParentDetail {
        public int Id { get; set; }
    }

}

Presently I iterate through ParentDetails and do some action for each ParentDetail. I am using MVC razor syntax so that’s the reason for the @( .. etc

@foreach (int index in Enumerable.Range(0, Model.Parent.ParentDetails.Count()))
{
  Model.Parent.ParentDetails[@index].Id

This gives me the numbers 1,2,3 … etc IF the Ids have been assigned sequentially in the list with the first element having an Id of 1 and the second element having an Id of 2 etc.

However the Ids in my list are not assigned sequentially. I may have it like this:

list-element [0] has an Id of 3
list-element [1] has an Id of 4
list-element [2] has an Id of 1
list-element [3] has an Id of 2

What I need is something equivalent to the foreach that will let me iterate through my list based on the value of Id. Maybe I need to use the Index method to find but I don’t know how to put this all into a loop.

I know some C# but this is quite far beyond me. Can anyone help out with some ideas. I hope my question makes sense.

I will watch for comments so please just send a comment if there is something that’s not clear.

Thank you.

Answer 1

LINQ is the super easy solution for such cases:

foreach(var details in Model.Parent.ParentDetails.OrderBy(d => d.Id))
{
    // details are processed in increasing order of Id here
}

You will need to add the System.Linq namespace with @using System.Linq if it’s not already included in your view.

Aside

Your existing code does things in a kind of roundabout way though. This:

@foreach (int index in Enumerable.Range(0, Model.Parent.ParentDetails.Count()))
{
    var x = Model.Parent.ParentDetails[@index].Id;
}

can also be written as

@foreach (var details in Model.Parent.ParentDetails)
{
    var x = details.Id;
}

which is the natural way of iterating over a collection, and far more preferable (unless you also need the index of each ParentDetails object in the collection).