List<DataRow>.DefaultIfEmpty() shows error

Question

I need to get a new DataRow from the List<DataRow> object.

Data object has 5 records / rows.

public List<DataRow> Data { get; set; } = new();

private DataRow GetDataRow(COAClassRecord _Record)
{
    DataRow _DataRow = (DataRow)Data.DefaultIfEmpty();
    _DataRow["Id"] = _Record.ID;
    _DataRow["Code"] = _Record.Code;
    _DataRow["Title"] = _Record.Title;
    return _DataRow;
}

But I got an error on this line:

DataRow _DataRow = (DataRow)Data.DefaultIfEmpty();

System.InvalidCastException: Unable to cast object of type 'DefaultIfEmptyIterator`1[System.Data.DataRow]' to type 'System.Data.DataRow'.

Kindly help me to find out how can I get a new DataRow through List<>.DefaultifEmpty or give be better way.

Answer 1

Make sure there is a default DataRow in case your returning list is empty. With that, you can use FirstOrDefault to get the DataRow from IEnumerable with Type <T>.

First, create a class in C# like below :

public class COAClassRecord
{
    public int ID { get; set; }
    public string Code { get; set; }
    public string Title { get; set; }
}

Then, Refer it to your program like below :

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;

public class Program
{
    public static void Main()
    {
        Sample example = new Sample();
        COAClassRecord record = new COAClassRecord { ID = 1, Code = "ABC", Title = "Sample Title" };
        DataRow row = example.GetDataRow(record);        
        Console.WriteLine($"Id: {row["Id"]}, Code: {row["Code"]}, Title: {row["Title"]}");
    }
}

public class Sample
{
    public List<DataRow> Data { get; set; } = new();

    public DataRow GetDataRow(COAClassRecord _Record)
    {
        DataRow _DataRow = Data.DefaultIfEmpty(CreateDefaultDataRow()).FirstOrDefault();
        if (_DataRow != null)
        {
            _DataRow["Id"] = _Record.ID;
            _DataRow["Code"] = _Record.Code;
            _DataRow["Title"] = _Record.Title;
        }
        return _DataRow;
    }

    private DataRow CreateDefaultDataRow()
    {
        
        DataTable table = new DataTable();
        table.Columns.Add("Id", typeof(int));
        table.Columns.Add("Code", typeof(string));
        table.Columns.Add("Title", typeof(string));

        
        return table.NewRow();
    }
}

Refer the working .netfiddle here