Createinstance in Typed class

Question

My intention is to recover mine Entity and the Repository by means of a string passed to the method.

With that I’ll make sure he can execute the GetAll() of my generic repository independent of the class that was passed, but I need to instantiate it.

So far the code is like this, but gives a null reference message on the line:

var entidades = (repository as RepositoryBase<EntityBase>).GetByFilter("1=1 AND " + filter);

Method:

public static MvcHtmlString SearchComboBox(string nameIdKey, object value, string controller, string tableName, string descriptionField, string filter = "1=1",  bool obrigatorio = false)
        {
        string options = string.Empty;

            Type type = AppDomain.CurrentDomain.GetAssemblies()
                .ToList()
                .FirstOrDefault(x => x.FullName.IndexOf("LaioMVC.Core") > -1)
                .GetTypes()
                .Where(x => x.Name.ToUpper() == tableName.ToUpper())
                .Single();

            EntityBase entity = null;

            if (type != null)
            {
                entity = (EntityBase)Activator.CreateInstance(type);

                Type typeRep = AppDomain.CurrentDomain.GetAssemblies()
                .ToList()
                .FirstOrDefault(x => x.FullName.IndexOf("LaioMVC.Data") > -1)
                .GetTypes()
                .Where(x => x.Name == tableName + "Repository")
                .Single();

                if (typeRep != null)
                {
                    var repository = Activator.CreateInstance(typeRep);

                    var entidades = (repository as RepositoryBase<EntityBase>).GetByFilter("1=1 AND " + filter);

                    for (int i = 0; i < entidades.Count(); i++)
                    {
                        Type campoKey = entity.GetType();
                        PropertyInfo info = campoKey.GetProperty(nameIdKey);

                        Type campoDescricao = entity.GetType();
                        PropertyInfo infoDesc = campoKey.GetProperty(nameIdKey);

                        options += Environment.NewLine;
                        options += string.Format("<option value='{0}'> {1} </option>", info.ToString(), infoDesc.ToString());
                    }
                }
            }

            return MvcHtmlString.Create(options);
        }

Repository:

using Dapper;
using LaioMVC.Core;
using LaioMVC.Core.Attributes;
using LaioMVC.Core.Models;
using LaioMVC.Core.ViewModels;
using LaioMVC.Data.Interfaces;
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations.Schema;
using System.Data.SqlClient;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;

namespace LaioMVC.Data.Repositorios
{
    public abstract class RepositoryBase<T> : IRepositoryBase<T>
            where T : EntityBase
    {
            public List<T> GetAll()
        {
            var query = $"select * from {typeof(T).Name} ";

            using (var connection = new SqlConnection(Constants.ConnectionString))
            {
                connection.Open();
                return connection.Query<T>(query).ToList();
            }
        }
    }
}

Entitybase:

namespace LaioMVC.Core.Models
{
    public class EntityBase 
    {
        public int Id { get; set; }
    }
}

Recalling that all entities inherit from EntityBase.

I wonder if someone could help me?