依赖注入：

Microsoft.Extensions.DependencyInjection 

using System.Data;


ServiceCollection sc = new ServiceCollection();
sc.AddTransient();
sc.AddTransient();
using (ServiceProvider spo = sc.BuildServiceProvider())
{
    IEnumerable dbs = spo.GetServices().Where(t=>t.GetType().Name== nameof(Mysql));
    
    foreach (var item in dbs)
    {
        item.ConStr = "xxxxxxxxxxxxxxxxxxxxxx";
        int i = item.Excute("update table set a=1 where a=2");
    }
    

}



interface IDbHelper
{
    public string ConStr { get; set; }
    DataTable Select(string sql);
    int Excute(string sql);
}
class Mysql : IDbHelper
{
    public string ConStr { get; set; } 
    public int Excute(string sql) {Console.WriteLine("Mysql Excute"); return 1; } 
    public DataTable Select(string sql) { Console.WriteLine("Mysql Select"); return null; }
}
class Oracle : IDbHelper
{
    public string ConStr { get; set; }
    public int Excute(string sql) { Console.WriteLine("Oracle Excute"); return 1; }
    public DataTable Select(string sql) { Console.WriteLine("Oracle Select"); return null; }
}
class DB2 : IDbHelper
{
    public string ConStr { get; set; }
    public int Excute(string sql) { Console.WriteLine("DB2 Excute"); return 1; }
    public DataTable Select(string sql) { Console.WriteLine("DB2 Select"); return null; }
}