Work with files, resources and preferences

Choose paths by ownership, preserve cancellation and keep private settings separate from distributable resources.

Use the right location#

Location	Purpose	Rule
App.ResourcePath	Assets packaged with the application	Read them; do not write back into the bundle.
AppPaths.DataFile(relativePath)	Per-application writable files	Use relative application data names, not traversal outside the application area.
A native picker result	A file or folder chosen by the user	Cancel returns no selection; check before reading or writing.
Settings	Small per-user scalar preferences	Not a secret store and not a replacement for a database.

Read and write deliberately#

File.ReadText and File.WriteText use strict UTF-8. A failed decode is a real error, not a reason to silently replace characters. The output directory must exist. File.WriteText replaces the target’s contents, so use it only for an intended destination. Use a disposable practice file in the service workbench.

Keep binary data binary#

ReadBytes returns a byte array. WriteBytes expects an allocated one-dimensional Byte array. Do not pass a text conversion of an image or a media file. Large downloads belong in the streaming download workflow rather than reading the entire response into a text variable.

Treat Cancel as a valid result#

Inside a Form with txtNotes; add Try/Catch around the file operation

Dim selected As String
selected = Dialogs.OpenFile("Choose a text file", "Text|*.txt")
If Len(selected) = 0 Then Exit Sub
txtNotes.Text = File.ReadText(selected)

A file can change or become inaccessible after selection. Handle the read/write failure even when the picker succeeded. The CommonDialog lesson covers the component-based dialog API as well.

Give preferences a default#

Per-application settings

Dim lastName As String
lastName = CStr(Settings.Get("last-name", ""))
Settings.Set "last-name", "Ada"

Settings persists supported scalar values. Use stable keys, provide a default when reading and avoid storing passwords, access tokens or entire object graphs. Logging should describe the action and outcome without copying those private values.

Keep platform integration bounded#

Path performs path manipulation without shell execution. Clipboard handles text exchange with the system clipboard. Platform exposes platform facts and supported URL opening. Environment intentionally exposes a controlled development/CI allowlist, not the entire process environment or secret keys.

Source baseline 20f4bfed6b · Build manifest