c# - trying to read one csv file and write to another but it is only writing the last line -

c# - trying to read one csv file and write to another but it is only writing the last line -

i trying read info 1 csv file , write another. when run programme lastly line written new file

while ((txtline = sr.readline()) != null) // reads 1 line variable txtline { //spiliting file columns if there in it. oldcolumns = txtline.split(','); //oldcolumns = regex.split(txtline,","); //writing oldcolumns info newcolumns. newcolumns[0] = oldcolumns[1]; newcolumns[1] = oldcolumns[0]; newcolumns[2] = ""; newcolumns[3] = oldcolumns[3]; newcolumns[4] = oldcolumns[4]; newcolumns[5] = ""; newcolumns[6] = ""; //using loop run through columns csvline = ""; (int = 0; < 7; i++) { csvline = csvline + "\"" + newcolumns[i].replace("\"","") + "\","; } } //writing file. sw.writeline(csvline);

move sw.writeline(csvline) within while loop:

while ((txtline = sr.readline()) != null) { ... sw.writeline(csvline); } // here, prints lastly line after exit loop

c# csv