using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var assemblyFiles = new AssemblyFiles(){

            Components = new List<ComponentFileData>(){

                new ComponentFileData(){ 

                    Type = "OMA", 

                    QuoteRequest = new QuoteRequest(){ Filename = "OMA" }

                },

                new ComponentFileData(){ 

                    Type = "INS", 

                    QuoteRequest = new QuoteRequest(){ Filename = "INS" }

                },

                new ComponentFileData(){ 

                    Type = "OM", 

                    QuoteRequest = new QuoteRequest(){ Filename = "OM" }

                }

            }

        };

        var substrateQuoteRequest = assemblyFiles.Components.FirstOrDefault(x => x.Type == "SS");

        var insertQuoteRequest = assemblyFiles.Components.FirstOrDefault(x => x.Type == "INS");

        if (substrateQuoteRequest != null)

        {

            Console.WriteLine("trying to process SS. ERROR!");

        }

        else if (insertQuoteRequest != null)

        {

            Console.WriteLine("trying to process INS");

        }

    }

}

​

public class AssemblyFiles

{

    public List<ComponentFileData> Components {get;set;}

}

​

public class ComponentFileData

{

    public string Type {get;set;}

    public QuoteRequest QuoteRequest {get;set;}

}

​

public class QuoteRequest

{

    public string Filename {get;set;}   

}