SHAutoComplete

C# Signature:

[DllImport("shlwapi.dll", ExactSpelling=true, PreserveSig=false)]
public static extern Int32 SHAutoComplete(
    IntPtr hwndEdit,
    AutoCompleteFlags dwFlags
);

VB .NET Signature:

Declare Function SHAutoComplete Lib "shlwapi.dll" (ByVal hWndEdit As IntPtr, ByVal dwFlags As AutoCompleteFlags) As Integer

Sample Code:

Int32 res = SHAutoComplete(textBox1.Handle, AutoCompleteFlags.SHACF_FILESYSTEM);