Multiple STA (Single Thread Apartment ) is not working in asp.net web application

protected void selectFolderbtn_Click(object sender, EventArgs e)
 {
     Thread thdSyncRead = new Thread(new ThreadStart(openfolder));
     thdSyncRead.SetApartmentState(ApartmentState.STA);
     thdSyncRead.Start();
 }

 public void openfolder()
 {

     FolderBrowserDialog fbd = new FolderBrowserDialog();
     DialogResult result = fbd.ShowDialog();

     string selectedfolder = fbd.SelectedPath;
     txt_extDestLoc.Text = selectedfolder;
      

 }

protected void selectFilebtn_Click(object sender, EventArgs e)
 {
     Thread thdSyncReadNew = new Thread(new ThreadStart(selectfile));
     thdSyncReadNew.SetApartmentState(ApartmentState.STA);
     thdSyncReadNew.Start();

    
     
 }

public void selectfile()
 {

     OpenFileDialog fileD = new OpenFileDialog(); //create object
     fileD.Filter = "Iso files|*.iso;"; //define filter
     fileD.ShowDialog(); //show dialog
     string globalisopath = fileD.FileName;
 
 }