How to change Input Language programmatically?

Do you know that your Windows Forms App could switch between installed languages at run-time?

An Input language is a Culture/Keyboard layout pair that determines how the physical keys on a keyboard map or plot to characters in a language (read more about Input Language in MSDN Library). Microsoft Windows allows installing more than one input language but international users usually use two: English and a national.

Since version 1.0 .NET Framework supports a special public sealed class - InputLanguage (in System.Windows.Forms namespace, assembly – System.Windows.Forms.dll). The property we are going to use today is CurrentInputLanguage of the InputLanguage type.

Enforcing to use a particular input language could be useful in many cases but please note that this function changes CurrentInputLanguage for the whole App and not just for a TextBox or any other selected control.

I created four overloaded functions that demonstrate this functionality. Actually only 4^th function (the only one in VB example) does change input language, first demonstrates how to switch between languages and two others - how to create a InputLanguage class based on  string or integer language codes (please see code comments for more details).

C# code:

 /// <summary>

 /// Changing Current Input Language to a next installed language

 /// </summary>

 public void ChangeInputLanguage()

 {

    // Nothing to do if there is only one Input Language supported:

     if (InputLanguage.InstalledInputLanguages.Count == 1)

        return;

    // Get index of current Input Language

     int currentLang = InputLanguage.InstalledInputLanguages.IndexOf(InputLanguage.CurrentInputLanguage);

    // Calculate next Input Language

     InputLanguage nextLang = ++currentLang == InputLanguage.InstalledInputLanguages.Count ? 

        InputLanguage.InstalledInputLanguages[0] : InputLanguage.InstalledInputLanguages[currentLang];

    // Change current Language to the calculated:

     ChangeInputLanguage(nextLang);

 }

 /// <summary>

 /// Changing current Input Language to a new one passed in the param

 /// </summary>

 /// <param name="ISOLang">ISO Culture name string code e.g. "en" for English</param>

 public void ChangeInputLanguage(string ISOLang)

 {

    // Convert ISO Culture name to InputLanguage object. Be aware: if ISO is not supported

     // ArgumentException will be invoked here

     InputLanguage nextLang = InputLanguage.FromCulture(new System.Globalization.CultureInfo(ISOLang));

    ChangeInputLanguage(nextLang);

 }

 /// <summary>

 /// Changing current Input Language to a new one passed in the param

 /// </summary>

 /// <param name="LangID">Integer Culture code e.g. 1033 for English</param>

 public void ChangeInputLanguage(int LangID)

 {

    // Convert Integer Culture code to InputLanguage object. Be aware: if Culture code is not supported

     // ArgumentException will be invoked here

     InputLanguage nextLang = InputLanguage.FromCulture(new System.Globalization.CultureInfo(LangID));

    ChangeInputLanguage(nextLang);

 }

 /// <summary>

 /// Changing current Input Language to a new one passed in the param

 /// </summary>

 /// <param name="InputLang">New Input Language as InputLanguage object</param>

 public void ChangeInputLanguage(InputLanguage InputLang)

 {

    // Check is this Language really installed. Raise exception to warn if it is not:

     if (InputLanguage.InstalledInputLanguages.IndexOf(InputLang) == -1)

        throw new ArgumentOutOfRangeException();

    // InputLAnguage changes here:

     InputLanguage.CurrentInputLanguage = InputLang;

 }

VB.NET code:

 Public Sub ChangeInputLanguage(ByVal InputLang As InputLanguage)

    If InputLanguage.InstalledInputLanguages.IndexOf(InputLang) = -1 Then

         Throw New ArgumentOutOfRangeException()

    End If

     InputLanguage.CurrentInputLanguage = InputLang

 End Sub

Happy New Year!

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