Parallel.Foreach C＃随机结果

Question

I want to read all result from a Dataset and insert a value by Mysql, but the insert take me random result:

Parallel.ForEach(table, new ParallelOptions { MaxDegreeOfParallelism = 2 }, row =>
{
    DataRow newrow = BDDestino.newrow("Cars");

    newrow["Code"] = row["CODE"];
    newrow["Name"] = row["NAME"];

    BD.insert(newrow); 
});

The content of the DataSet/DataTable"table" is great, but the insert in the Mysql table is random.

If my rows are

1, 2, 3, 4

The insert sometimes is: 2,3

or: > 1,2,3

I need ALL rows in order.

Edit: I thought that Parallel.ForEach sentences can insert whit order and very fast, but i see that Parallel.ForEach doesn't do it itself. Like @juharr says, this sentence maybe can be worst. Thanks to all.

Answer 1

If you use parallelism, you cannot guarantee the order in which .insert() is called (as you found).

Somehow you need to fix that order in advance:

• Use array indexes, which can be pre-calculated from the existing table.

   DataRow[] bdArray = new DataRow[table.RowCount]; Parallel.ForEach(table, new ParallelOptions { MaxDegreeOfParallelism = 2 }, row => { DataRow newrow = BDDestino.newrow("Cars"); newrow["Code"] = row["CODE"]; newrow["Name"] = row["NAME"]; // Add the new row in a pre-arranged position int index = table.indexOf(row); bdArray[index] = newrow; }); 

Or maybe it doesn't matter... you can always sort them afterwards.