OpenFileDialog openFileDialogModele = new OpenFileDialog();
openFileDialogModele.Filter = "Text files (*.txt)|*.txt|All files (*.*)|*.*";
openFileDialogModele.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory);
 
DialogResult result = openFileDialogModele.ShowDialog();
if (result == DialogResult.OK) 
{
    textBoxModele.Text = openFileDialogModele.FileName;
}

System.IO.StreamReader file = new System.IO.StreamReader(textBoxIdModele.Text);
string Text = file.ReadToEnd();
file.Close();

List<string> lines = new List<string>();
 
string line;
System.IO.StreamReader file = new System.IO.StreamReader(@"c:\test.txt");
while ((line = file.ReadLine()) != null)
{
   lines.Add(line);
}

System.IO.File.WriteAllText(@"C:\Users\Public\TestFolder\WriteText.txt", text);

string Path;
 
FolderBrowserDialog folderBrowserDialog = new FolderBrowserDialog();
folderBrowserDialog.RootFolder = Environment.SpecialFolder.DesktopDirectory;
if (folderBrowserDialog.ShowDialog() == DialogResult.OK)
{
    Path = folderBrowserDialog.SelectedPath;
}