Even through the property does not appear in the Properties window or in Intellisense (that I can see), it compiles if you just type it in:
Code Snippet
' Add a text string to the TextBox.
TextBox1.Text =
"Hello World!"
' Set the size of the TextBox.
TextBox1.AutoSize =
True
However, it does not appear to work at one might think it does. It does not resize the textbox width, it resizes the height based on the font. This is from the documentation:
"Gets or sets a value indicating whether the height of the control automatically adjusts when the font assigned to the control is changed. "