how to return result of a linq query in c#?

Question

Hi every body

I have a joined query in linq and I put this query into a function .

I don't know what type should I set instead of void for this function to return data for me.

plz see the code:

        private void GetPaintDetails(byte formId)         {             var query = from f in Paint_FormBLL.GetAll()                         join col in Paint_FormColumnBLL.GetAll() on f.FormId equals col.FormId into fcoll                         from _fcol in fcoll.DefaultIfEmpty()                         join cell in Paint_FormCellBLL.GetAll() on _fcol.ColumnId equals cell.ColumnId into fcell                         from _fcell in fcell.DefaultIfEmpty()                         where f.FormId == formId                         select new                         {                             FormId = f.FormId,                             ColumnId = _fcol.ColumnId,                             ColumnName = _fcol.ColumnName,                             CellId = _fcell.CellId,                             CellValue = _fcell.CellValue                         };         }

Answer 1

Hi @Farshad Valizade , Welcome to Microsoft Q&A,

Usually we construct a class for the required data and then return its collection: IEnumerable<T> or IQueryable<T>.

You can also return an object, or the result of a calculation.

What type is returned usually depends on what you need.

I wrote an example for you to understand:

namespace _9_26_x
{
    using System;
    using System.Collections.Generic;
    using System.Linq;

    public class PaintDetails
    {
        public byte FormId { get; set; }
        public int? ColumnId { get; set; }
        public string ColumnName { get; set; }
        public int? CellId { get; set; }
        public string CellValue { get; set; }
    }

    public class Paint_FormBLL
    {
        public static List<Paint_Form> GetAll()
        {
            // Assume that data is obtained from a database or other data source
            return new List<Paint_Form>
        {
            new Paint_Form { FormId = 1 },
            new Paint_Form { FormId = 2 },
        };
        }
    }

    public class Paint_FormColumnBLL
    {
        public static List<Paint_FormColumn> GetAll()
        {
            // Assume that data is obtained from a database or other data source
            return new List<Paint_FormColumn>
        {
            new Paint_FormColumn { ColumnId = 1, FormId = 1, ColumnName = "Column A" },
            new Paint_FormColumn { ColumnId = 2, FormId = 1, ColumnName = "Column B" },
            new Paint_FormColumn { ColumnId = 3, FormId = 2, ColumnName = "Column C" },
        };
        }
    }

    public class Paint_FormCellBLL
    {
        public static List<Paint_FormCell> GetAll()
        {
            // Assume that data is obtained from a database or other data source
            return new List<Paint_FormCell>
        {
            new Paint_FormCell { CellId = 1, ColumnId = 1, CellValue = "Value 1" },
            new Paint_FormCell { CellId = 2, ColumnId = 2, CellValue = "Value 2" },
            new Paint_FormCell { CellId = 3, ColumnId = 3, CellValue = "Value 3" },
        };
        }
    }

    public class Paint_Form
    {
        public byte FormId { get; set; }
    }

    public class Paint_FormColumn
    {
        public int ColumnId { get; set; }
        public byte FormId { get; set; }
        public string ColumnName { get; set; }
    }

    public class Paint_FormCell
    {
        public int CellId { get; set; }
        public int ColumnId { get; set; }
        public string CellValue { get; set; }
    }

    public class Program
    {
        public static void Main()
        {
            byte formId = 1;
            var paintDetails = GetPaintDetails(formId);

            foreach (var detail in paintDetails)
            {
                Console.WriteLine($"FormId: {detail.FormId}, ColumnId: {detail.ColumnId}, ColumnName: {detail.ColumnName}, CellId: {detail.CellId}, CellValue: {detail.CellValue}");
            }
            Console.ReadLine();
        }

        private static IEnumerable<PaintDetails> GetPaintDetails(byte formId)
        {
            var query = from f in Paint_FormBLL.GetAll()
                        join col in Paint_FormColumnBLL.GetAll() on f.FormId equals col.FormId into fcoll
                        from _fcol in fcoll.DefaultIfEmpty()
                        join cell in Paint_FormCellBLL.GetAll() on _fcol?.ColumnId equals cell.ColumnId into fcell
                        from _fcell in fcell.DefaultIfEmpty()
                        where f.FormId == formId
                        select new PaintDetails
                        {
                            FormId = f.FormId,
                            ColumnId = _fcol?.ColumnId,
                            ColumnName = _fcol?.ColumnName,
                            CellId = _fcell?.CellId,
                            CellValue = _fcell?.CellValue
                        };

            return query.ToList();
        }
    }

}

Best Regards,

Jiale

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