The example Localize a program's user interface to work in multiple languages and locales in C# explains how to localize a program so it displays different user interfaces depending on the system's locale. The example Test a localized program that works in multiple languages and locales in C# explains how you can select a specific locale when the program starts so you can test different locales.

This example lets you select a specific locale at run time.

The SetCulture method shown below selects a specific culture.

// Set the form's culture.
private void SetCulture(string culture)
{
    // Make the CultureInfo.
    CultureInfo culture_info = new CultureInfo(culture);

    // Make a ComponentResourceManager.
    ComponentResourceManager component_resource_manager
        = new ComponentResourceManager(this.GetType());

    // Apply resources to the form.
    component_resource_manager.ApplyResources(
        this, "$this", culture_info);

    // Apply resources to the form's controls.
    foreach (Control ctl in this.Controls)
    {
        component_resource_manager.ApplyResources(
            ctl, ctl.Name, culture_info);
    }
}

The code makes a new CultureInfo object to represent the culture. It then makes a ComponentResourceManager for the culture and uses its ApplyResources method to load the culture-specific resources for the form and its controls.

The following code shows how the example loads its resources for English or German when you select a radio button.

private void radEnglish_Click(object sender, EventArgs e)
{
    SetCulture("en-US");
}

private void radGerman_Click(object sender, EventArgs e)
{
    SetCulture("de-DE");
}

(This example actually isn't localized for English but that's what I used when making the default localization so that's what you get if you select en-EN or any other culture for which it isn't localized. For example, try fr-FR or es-MX.)