I am new to C# and OOP, in general, I've kinda hit a wall I am reading in this CSV using the CSV Helper package, but there are some unwanted rows, etc so I have cleaned it up by iterating over "records" and creating a new class LineItems.

But Now I appear to be a bit stuck. I know void doesn't return anything and is a bit of a placeholder. But How can I access all the instances of LineItems outside of this function?

public void getMapper()
        {
            using (var StreamReader = new StreamReader(@"D:\Data\Projects\dictUnitMapper.csv"))
            {
                using (var CsvReader = new CsvReader(StreamReader, CultureInfo.InvariantCulture))
                {
                    var records = CsvReader.GetRecords<varMapper>().ToList();
               
                foreach (var item in records)
                {
                    if (item.name != "#N/A" && item.priority != 0)
                    {
                        LineItems lineItem = new LineItems();

                        lineItem.variableName = item.Items;
                        lineItem.variableUnit = item.Unit;
                        lineItem.variableGrowthCheck = item.growth;
                        lineItem.variableAVGCheck = item.avg;
                        lineItem.variableSVCheck = item.svData;
                        lineItem.longName = item.name;
                        lineItem.priority = item.priority;
                        
                    }
                }
            }
            
        }
    }
    public class LineItems
    {
        public string variableName;
        public string variableUnit;
        public bool variableGrowthCheck;
        public bool variableAVGCheck;
        public bool variableSVCheck;
        public string longName;
        public int priority;
    }

    public class varMapper
    {

        public string Items { get; set; }
        public string Unit { get; set; }
        public bool growth { get; set; }
        public bool avg { get; set; }
        public bool svData { get; set; }
        public string name { get; set; }
        public int priority { get; set; }
    }

CodePudding user response：

You can return a collection of LineItems from the function:

1. Change your LineItems class name to LineItem.

2. Change return type of GetMapper function from void to something that represents a collection. Using IEnumerable in example below, it would be a good choice if you don't need to alter the collection after returning.

    public IEnumerable<LineItem> GetMapper()
    {
      ...
      // Don't call .ToList, let GetRecords return a yielded IEnumerable
      var records = CsvReader.GetRecords<varMapper>();

      var lineItems = new List<LineItem>();
    
      foreach (var item in records)
      {
        var lineItem = new LineItem();
        // map
        lineItems.Add(lineItem);
      }
    
      return lineItems;
    }

Not to jump too far ahead, but if you do not want to load the entirety of the file into a list in memory, you can/should utilize yield

    public IEnumerable<LineItem> GetMapper()
    {
      ...
      // Don't call .ToList, let GetRecords return a yielded IEnumerable
      var records = CsvReader.GetRecords<varMapper>();

      foreach (var item in records)
      {
        var lineItem = new LineItem();
        // map
        yield return lineItem;
      }
    }

CodePudding user response：

You should write your method to return a list.

public List<LineItems> GetMapper()
{
    using (var StreamReader = new StreamReader(@"D:\Data\Projects\dictUnitMapper.csv"))
    {
        using (var CsvReader = new CsvHelper.CsvReader(StreamReader, CultureInfo.InvariantCulture))
        {
            return
                CsvReader
                    .GetRecords<varMapper>()
                    .Where(item => item.name != "#N/A")
                    .Where(item => item.priority != 0)
                    .Select(item => new LineItems()
                    {

                        variableName = item.Items,
                        variableUnit = item.Unit,
                        variableGrowthCheck = item.growth,
                        variableAVGCheck = item.avg,
                        variableSVCheck = item.svData,
                        longName = item.name,
                        priority = item.priority,
                    })
                    .ToList();
        }
    }
}

Here's an alternative syntax for building the return value:

            return
            (
                from item in CsvReader.GetRecords<varMapper>()
                where item.name != "#N/A"
                where item.priority != 0
                select new LineItems()
                {
                    variableName = item.Items,
                    variableUnit = item.Unit,
                    variableGrowthCheck = item.growth,
                    variableAVGCheck = item.avg,
                    variableSVCheck = item.svData,
                    longName = item.name,
                    priority = item.priority,
                }
            ).ToList();