IT will work with code below , example for Japanese
foreach (System.Windows.Forms.InputLanguage lang in System.Windows.Forms.InputLanguage.InstalledInputLanguages)
if (lang.LayoutName == "Japanese")
{
System.Windows.Forms.InputLanguage.CurrentInputLanguage = lang;
InputMethod.Current.ImeState = InputMethodState.On;
}
or simple set in xaml
InputMethod.IsInputMethodEnabled="True" InputLanguageManager.InputLanguage="ja-JP"