Declare a variable per thread and manage them in c# Parallel.Foreach [closed]

Finally I solved it in a sequential way, by putting the records in a table and making a SqlBulkCopy against the DB, following the advices.

DataTable table = getDataTable();

myList.ForEach(element => {
    
    //...
    
    table.Rows.Add(getRow(element));

    if (decimal.Remainder(counter, 500) == 0){
        SqlConnection _db;
        _db.Open();
        
        using (SqlBulkCopy bulk = new SqlBulkCopy(_db)){
            var map1 = new SqlBulkCopyColumnMapping("columnName1", "columnName1");
            var map2 = new SqlBulkCopyColumnMapping("columnName2", "columnName2");
            //...
            
            bulk.ColumnMappings.Add(map1);
            bulk.ColumnMappings.Add(map2);
            //...
            
            bulk.DestinationTableName = "DestinationTableName";
            bulk.WriteToServer(table);

            bulk.Close();
        }
    }
}