c# - SQLBulkCopy slower than expected -

it's taking around 5 minutes per million records, wondering if expected speed.

i wondering if batch size small i.e. 500 ?

my current code looks this...

using (var destinationconnection = new sqlconnection(settings.default.batchoutputconnectionstring)) {     var tablename = mergedfilename.substring(0, mergedfilename.indexof('.'));     destinationconnection.open();      try     {         using (var createanddroptablecommand = new sqlcommand("sp_dropandcreatetable", destinationconnection))         {             createanddroptablecommand.commandtype = commandtype.storedprocedure;             createanddroptablecommand.parameters.add("@tabletocreate", sqldbtype.varchar).value = tablename;             createanddroptablecommand.executenonquery();         }          foreach (var file in txtfiles)         {             using (var lineiterator = file.readlines(file).getenumerator())             {                 while (lineiterator.movenext())                 {                     var line = lineiterator.current;                     var datacolumns = line.split('\t');                     var dr = dt.newrow();                      (var = 0; < datacolumns.length; i++)                     {                         dr[i] = datacolumns[i].trim().length == 0 ? null : datacolumns[i];                     }                      dt.rows.add(dr);                     recordcounter++;                 }                 using (var bulkcopy = new sqlbulkcopy(destinationconnection))                 {                     bulkcopy.destinationtablename = "dbo." + tablename;                     bulkcopy.batchsize = 500;                     bulkcopy.columnmappings.clear();                     foreach (datacolumn col in dt.columns)                     {                         bulkcopy.columnmappings.add(new sqlbulkcopycolumnmapping(col.columnname, col.columnname));                     }                      bulkcopy.writetoserver(dt);                 }                 dt.clear();             }         }     }         {         destinationconnection.close();     } }