---

<RadioButton Content="Москва"       GroupName="City" Click="City_Checked"/>
    <RadioButton Content="Лондон"       GroupName="City" Click="City_Checked"/>
    <RadioButton Content="Париж"        GroupName="City" Click="City_Checked"/>
    <RadioButton Content="Дубай"        GroupName="City" Click="City_Checked"/>
    <RadioButton Content="Токио"        GroupName="City" Click="City_Checked"/>
    <RadioButton Content="Пекин"        GroupName="City" Click="City_Checked"/>
    <RadioButton Content="Нью-Йорк"     GroupName="City" Click="City_Checked"/>
    <RadioButton Content="Лос-Анджелес" GroupName="City" Click="City_Checked"/>
    <RadioButton Content="Сидней"       GroupName="City" Click="City_Checked"/>
    <RadioButton Content="Дели"         GroupName="City" Click="City_Checked"/>
    <RadioButton Content="Берлин"       GroupName="City" Click="City_Checked"/>
    <RadioButton Content="Сан-Паулу"    GroupName="City" Click="City_Checked"/>
    <TextBlock x:Name="tbResult" FontSize="16" Margin="0,20,0,0"
               HorizontalAlignment="Center" Foreground="DarkBlue"/>

private void City_Checked(object sender, RoutedEventArgs e)
{
    RadioButton rb = sender as RadioButton;
    if (rb == null || rb.IsChecked != true) return;

    Dictionary<string, string> timezones = new Dictionary<string, string>
    {
        {"Москва",       "GMT+3"},
        {"Лондон",       "GMT+0"},
        {"Париж",        "GMT+1"},
        {"Дубай",        "GMT+4"},
        {"Токио",        "GMT+9"},
        {"Пекин",        "GMT+8"},
        {"Нью-Йорк",     "GMT-5"},
        {"Лос-Анджелес", "GMT-8"},
        {"Сидней",       "GMT+10"},
        {"Дели",         "GMT+5:30"},
        {"Берлин",       "GMT+1"},
        {"Сан-Паулу",    "GMT-3"}
    };

    string city = rb.Content.ToString();
    if (timezones.ContainsKey(city))
        tbResult.Text = $"{city} – {timezones[city]}";
}