Mapping takes long time for bulk data

When I retrieve data from SQL Server, it takes 2 minutes for bulk data (2000000 rows) in SQL query window. But it takes long time (approximately 20 minutes or more) for mapping as a list using dapper ORM.

Is there any idea to increase the performance in mapping.

This is my code:

public List<T> DapperToList<T>(string SqlQuery, CommandType? CommandType = null) where T : class
{
    if (Con.State == ConnectionState.Open)
        Con.Close();

    Con.Open();

    var result = this.Con.Query<T>(SqlQuery, null, null, true, int.MaxValue, CommandType).ToList();

    Con.Close();

    return result;
}

public List<LOG_REPORTS> REPORT_LOG(DateTime? FROMDATE, DateTime? TODATE)
{
    DynamicParameters param = new DynamicParameters();

    param.Add("@FROMDATE", FROMDATE, DbType.DateTime);
    param.Add("@TODATE", TODATE, DbType.DateTime);

    var lstt = db.DapperToList<LOG_REPORTS>("PROC_LOG_REPORTS", param, CommandType.StoredProcedure);

    return lstt;
}