.net - How to append data to file using SaveFileDialog -

i want write data file, use savefiledialog object:

public class form3     inherits form     public callerform3to1 form1      dim filestream stream = nothing     dim filesw streamwriter = nothing      private sub form3_load(sender object, e eventargs) handles mybase.load         savefiledialog1.filter = "txt files (*.txt)|*.txt|all files (*.*)|*.*"         savefiledialog1.filterindex = 2         savefiledialog1.restoredirectory = true          flagwritetofile = false          if savefiledialog1.showdialog() = dialogresult.ok             btn_writedata.enabled = true         end if      end sub     'some code end class 

and after write data opened file:

sub writedatatotext(data long(), appenddata boolean)     'dim new streamwriter(savefiledialog1.openfile(), filemode.append) ' error!     filesw = new streamwriter(savefiledialog1.openfile())     if (filesw isnot nothing)          filesw.writeline(string.join(" ", data) + environment.newline)         filesw.close()     end if end sub 

what want: need append data file, , overwrite. create appenddata this: if 1 append if 0 overwrite. know can create streamwriter file , use filemode purposes. if use savefiledialog it's method openfile returns stream! , cannot create streamwriter constructor (it takes string not stream).

how append data file using savefiledialog?

you cannot use openfile append data file selected in savefiledialog.
in msdn documentation savefiledialog.openfile can read

for security purposes, method creates new file selected name , opens read/write permissions. can cause unintentional loss of data if select existing file save to. save data existing file while retaining existing data, use file class open file using file name returned in filename property.

so should write code using filename property streamwriter constructor accepts boolean true append data or false overwrite file.

sub writedatatotext(data long(), appenddata boolean)     using filesw = new streamwriter(savefiledialog1.filename, appenddata)         filesw.writeline(string.join(" ", data) + environment.newline)     end using end sub 

remember use using statement around these disposable object sure correct closing , disposing of stream , avoid locking conditions

instead using file class write

 dim newline = string.join(" ", data) + environment.newline)  if appenddata      file.appendalltext(savefiledialog1.filename, newline)  else      file.writealltext(savefiledialog1.filename, newline)  end if