// nullable disable

using System;

using System.Data;

using Microsoft.EntityFrameworkCore;

using Microsoft.EntityFrameworkCore.Diagnostics;

using System.Collections.Generic;

using OneOf;

using System.ComponentModel;

​

public class Program

{

    public static void Main()

    {

        var reportRepo = new ReportRepository();

        var result = reportRepo.GetReport("VwExampleReport1");

        //var result = reportRepo.GetReport("VwExampleReport2");

        //Console.WriteLine("Test");

        Console.WriteLine("{0}", result.Columns[0]);

    }

}

​

// Database Table Classes

public class VwExampleReport1

{

    public int VwExampleReport1Id { get; set; }

}

​

public class VwExampleReport2

{

    public int VwExampleReport2Id { get; set; }

}

​

// DBContext

public partial class ReportContext : DbContext

{

    public ReportContext(DbContextOptions<ReportContext> options) : base(options)

    {

    }

​

    public virtual DbSet<VwExampleReport1> VwExampleReport1 { get; set; }

    public virtual DbSet<VwExampleReport2> VwExampleReport2 { get; set; }

}

​

// "Discriminated Union"

public abstract record Report()

{

    public sealed record VwExampleReport1(DbSet<VwExampleReport1> ReportDbSet) : Report();

    public sealed record VwExampleReport2(DbSet<VwExampleReport2> ReportDbSet) : Report();

}

​

// Repository

public interface IReportRepository

{

    DataTable GetReport(string reportName);

}

​

public class ReportRepository() : IReportRepository

{

    private readonly string encodingType = "iso-8859-1";

    public DataTable GetReport(string reportName)

    {

        var dbOptions = new DbContextOptionsBuilder<ReportContext>()

            .UseInMemoryDatabase("BloggingControllerTest")

            .ConfigureWarnings(b => b.Ignore(InMemoryEventId.TransactionIgnoredWarning))

            .Options;

        try

        {

            using ReportContext db = new(dbOptions);

            db.Database.EnsureDeleted();

            db.Database.EnsureCreated();

            db.VwExampleReport1.Add(new VwExampleReport1 { VwExampleReport1Id = 1 });

            db.VwExampleReport2.Add(new VwExampleReport2 { VwExampleReport2Id = 1 });

            // Get Data for Report

            OneOf<VwExampleReport1[], VwExampleReport2[]> getReportResult = GetReportData(reportName, db);

            return getReportResult.Match

            (

                vwExampleReport1 => vwExampleReport1.ToDataTable(), 

                vwExampleReport2 => vwExampleReport2.ToDataTable()

            );

        }

        catch (Exception ex)

        {

            Console.WriteLine("{0}", ex.Message);

            return null;

        }

    }

​

    private OneOf<VwExampleReport1[], VwExampleReport2[]> GetReportData(string reportName, ReportContext db) => reportName switch

    {

        "VwExampleReport1" => db.VwExampleReport1.ToArrayAsync().Result,

        "VwExampleReport2" => db.VwExampleReport2.ToArrayAsync().Result

    };

}

​

// Extensions

public static class DataTableConverter

{

    public static DataTable ToDataTable<T>(this ICollection<T> data)

    {   

        PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(typeof(T));

        DataTable table = new DataTable();

        foreach (PropertyDescriptor prop in properties)

            table.Columns.Add(prop.Name, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType);

        foreach (T item in data)

        {

            DataRow row = table.NewRow();

            foreach (PropertyDescriptor prop in properties)

                row[prop.Name] = prop.GetValue(item) ?? DBNull.Value;

            table.Rows.Add(row);

        }

​

        return table;

    }

}