c# - How to queue up system process start -

i've written following code loop around load of data table rows , generate pdf if doesn't exist. works, launches wkhtmltopdfs in 1 go 30 processes started , kill server, d'oh!

what's best way launch 1 process @ time , not start second until previous 1 has run?

   db db = new db();             datatable dtposters = db.getdatatable("select * invoices pdfgenerated <> 1 or pdfgenerated null");              foreach (datarow dr in dtposters.rows)             {                 //generate poster, if exsists (don't!)                 directory.createdirectory(string.format("d:\\invoices\\"));                 string filepath = string.format("d:\\invoices\\{0}.pdf", dr["invoicenumber"].tostring());                 if (!file.exists(filepath))                 {                     string cmd = string.format("c:\\services\\automafe\\wkhtmltopdf.exe http://invoicegen/viewinvoice.aspx?invoicenumber={0} {1}", dr["invoicenumber"].tostring(), filepath);                     system.diagnostics.process.start("cmd", "/c " + cmd);                  }                 else                 {                      //update db                  }              }  

process.start returns process object, lets monitor state of newly-created process.

a simple, blocking way have each worker wait process exit

var myprocess = system.diagnostics.process.start("cmd", "/c " + cmd); myprocess.waitforexit(); 

a better way use exited event handler monitor when process exits.

var myprocess = system.diagnostics.process.start("cmd", "/c " + cmd); myprocess.exited += myprocessfinishedhandler;