ru.stackoverflow.com/questions/785612

using System;
using System.Linq;
using System.Collections.ObjectModel;
using System.Collections.Generic;
using System.Reflection;

public interface IDbConnection { }
public interface IDbTransaction { }
public class CommandDefinition { }
public class DapperRow { }
public enum CommandType { }

public static class SqlMapper
{
    public static IEnumerable<dynamic> Query(this IDbConnection cnn, string sql, object param = null, IDbTransaction transaction = null, bool buffered = true, int? commandTimeout = null, CommandType? commandType = null) => null;
    public static IEnumerable<T> Query<T>(this IDbConnection cnn, CommandDefinition command) => null;

    public static IEnumerable<T> Query<T>(this IDbConnection cnn, string sql, object param = null, IDbTransaction transaction = null, bool buffered = true, int? commandTimeout = null, CommandType? commandType = null)
    where T : new()
    {
        return (new T[] { new T() });
    }

    public static IEnumerable<TReturn> Query<TFirst, TSecond, TReturn>(this IDbConnection cnn, string sql, Func<TFirst, TSecond, TReturn> map, object param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null) => null;
    public static IEnumerable<TReturn> Query<TFirst, TSecond, TThird, TReturn>(this IDbConnection cnn, string sql, Func<TFirst, TSecond, TThird, TReturn> map, object param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null) => null;
    public static IEnumerable<TReturn> Query<TFirst, TSecond, TThird, TFourth, TReturn>(this IDbConnection cnn, string sql, Func<TFirst, TSecond, TThird, TFourth, TReturn> map, object param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null) => null;
    public static IEnumerable<TReturn> Query<TFirst, TSecond, TThird, TFourth, TFifth, TReturn>(this IDbConnection cnn, string sql, Func<TFirst, TSecond, TThird, TFourth, TFifth, TReturn> map, object param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null) => null;
    public static IEnumerable<TReturn> Query<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TReturn>(this IDbConnection cnn, string sql, Func<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TReturn> map, object param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null) => null;
    public static IEnumerable<TReturn> Query<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(this IDbConnection cnn, string sql, Func<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn> map, object param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null) => null;
    public static IEnumerable<TReturn> Query<TReturn>(this IDbConnection cnn, string sql, Type[] types, Func<object[], TReturn> map, object param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null) => null;
}

class Solution
{
    public class baseTable { }
    public class LOGS : baseTable { }
    public class TRACK_EVENT : baseTable { }

    public static class MNLZContext
    {
        public class DbConnection : IDbConnection { }
        public static IDbConnection oracleConnect = new DbConnection();
    }

    public Dictionary<string, object> dbTables = new Dictionary<string, object>();

    public object getTableRows(string tableName, string sqlWhere = @"")
    {
        // взять тип таблицы, сидящей в dbTables[tableName]
        Type tableType = dbTables[tableName].GetType();

        // проверить полученный тип
        if (tableType.GetGenericTypeDefinition() != typeof(ObservableCollection<>))
            throw new ArgumentException("Непонятный класс элемента dbTables[tableName]");

        // взять единственный generic-аргумент сконструированного класса ObservableCollection<T>
        Type itemType = tableType.GetGenericArguments()[0];

        // получить обобщённый метод SqlMapper.Query<T>(this IDbConnection cnn, string sql, object param = null, IDbTransaction transaction = null, bool buffered = true, int? commandTimeout = null, CommandType? commandType = null)
        MethodInfo generic_method = typeof(SqlMapper).GetMethods()
            .Where(m => m.Name.Equals("Query"))
            .Where(m => m.IsStatic)
            .Where(m => m.GetParameters().Length == 7)
            .Where(m => m.GetParameters()[0].ParameterType == typeof(IDbConnection))
            .Where(m => m.GetParameters()[1].ParameterType == typeof(string))
            .Where(m => m.GetParameters()[2].ParameterType == typeof(object))
            .Where(m => m.GetParameters()[3].ParameterType == typeof(IDbTransaction))
            .Where(m => m.GetParameters()[4].ParameterType == typeof(bool))
            .Where(m => m.GetParameters()[5].ParameterType == typeof(int?))
            .Where(m => m.GetParameters()[6].ParameterType == typeof(CommandType?))
            .Where(m => m.ContainsGenericParameters)
            .Single();
        // создать сконструированный метод SqlMapper.Query<itemType>(IDbConnection, string, object, IDbTransaction, bool, int?, CommandType?)
        MethodInfo constructed_method = generic_method.MakeGenericMethod(new Type[] { itemType });

        // строка запроса
        string oracleSelectAllTableRows = @"SELECT * FROM " + tableName + ' ' + sqlWhere;
        // формируем список параметров для вызова
        object[] call_parameters = new object[]
        {
            MNLZContext.oracleConnect,
            oracleSelectAllTableRows,
            constructed_method.GetParameters()[2].DefaultValue,
            constructed_method.GetParameters()[3].DefaultValue,
            constructed_method.GetParameters()[4].DefaultValue,
            constructed_method.GetParameters()[5].DefaultValue,
            constructed_method.GetParameters()[6].DefaultValue
        };
        // делаем вызов сконструированного метода, чтобы получить новый набор данных 'tableRows'
        // IEnumerable<itemType> tableRows = MNLZContext.oracleConnect.Query<itemType>(oracleSelectAllTableRows);
        // IEnumerable<itemType> tableRows = SqlMapper.Query<itemType>(MNLZContext.oracleConnect, oracleSelectAllTableRows[, null, null, true, null, null]);
        // поскольку вызывается статический метод, то первый параметр .Invoke() ставим 'null' (объекта нет)
        object tableRows = constructed_method.Invoke(null, call_parameters);

        // конструируем тип IEnumerable<itemType>
        Type ienumerableType = typeof(IEnumerable<>).MakeGenericType(new Type[] { itemType });
        // запрашиваем у типа таблицы ObservableCollection<itemType> подходящий конструктор
        ConstructorInfo constructor = tableType.GetConstructors()
            .Where(c => c.GetParameters().Length == 1)
            .Where(c => c.GetParameters()[0].ParameterType.IsEquivalentTo(ienumerableType))
            .Single();

        // конструируем и возвращаем коллекцию 'ObservableCollection<itemType>(tableRows)'
        return constructor.Invoke(new object[] { tableRows });
    }

    public void Prepare()
    {
        dbTables["test1"] = new ObservableCollection<LOGS>(Enumerable.Repeat(new LOGS(), 3));
        dbTables["test2"] = new ObservableCollection<TRACK_EVENT>(Enumerable.Repeat(new TRACK_EVENT(), 4));
    }

    public void PrintInfo(string tableName, string addition)
    {
        Console.WriteLine($"  {addition}: dbTables[\"{tableName}\"]'s type is '{dbTables[tableName].GetType().Name}<{dbTables[tableName].GetType().GetGenericArguments()[0].Name}>'");

        if (dbTables[tableName] is ObservableCollection<LOGS> t_1)
        {
            Console.WriteLine($"  {addition}: dbTables[\"{tableName}\"].Count = {t_1.Count}");
            Console.WriteLine($"  {addition}: dbTables[\"{tableName}\"]'s item[0] type is '{t_1[0].GetType().Name}'");
        }
        else if (dbTables[tableName] is ObservableCollection<TRACK_EVENT> t_2)
        {
            Console.WriteLine($"  {addition}: dbTables[\"{tableName}\"].Count = {t_2.Count}");
            Console.WriteLine($"  {addition}: dbTables[\"{tableName}\"]'s item[0] type is '{t_2[0].GetType().Name}'");
        }
        else
            throw new Exception("Что-то поломалось в типах элементов 'dbTables[]'");
    }

    public void Test()
    {
        foreach (string tableName in dbTables.Keys.ToList())
        {
            Console.WriteLine($"key: '{tableName}'");
            PrintInfo(tableName, "old");
            dbTables[tableName] = getTableRows(tableName);
            PrintInfo(tableName, "new");
        }

        Console.WriteLine("==========");
    }

    static void Main(string[] args)
    {
        Solution test_object = new Solution();
        test_object.Prepare();
        test_object.Test();
        test_object.Test();
    }
}