Text to Speech in WPF

One of the new features that came out with .NET 3.5 and 4.0 is the addition of the System.Speech library. This library is a collection of classes that enables speech recognition and speech synthesis (text-to-speech). 

Speech synthesis artificially produces human speech and talk to users. Windows 7's Text-To-Speech (TTS) engine converts text in a specific language into speech. The speech synthesis engine is accessed directly in managed applications by using the classes in System.Speech.Synthesis or, alternatively, by the Speech API (SAPI) when used in unmanaged applications.

 

 

Here is a small sample of using the System.Speech.Synthesis. Add a reference to System.Speech.

 

Create WPF window as below

<Window x:Class="Text_to_Speech.MainWindow"

        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

        Title="MainWindow" Height="400" Width="600" Loaded="Window_Loaded">

    <Grid Width="auto" Height="auto">

        <Label Content="Voice:" Height="28" HorizontalAlignment="Left" Margin="12,12,0,0" Name="label3" VerticalAlignment="Top" Width="45" />        <ComboBox Height="23" HorizontalAlignment="Left" Margin="54,12,0,0" Name="comboVoice" ItemsSource="{Binding}" VerticalAlignment="Top" Width="110" />

        <Label Height="28" HorizontalAlignment="Left" Margin="182,12,0,0"

               Name="label1" VerticalAlignment="Top" Width="54">Volume:</Label>

        <Slider Height="23" HorizontalAlignment="Left" Margin="231,12,0,0" Name="sliderVolume" VerticalAlignment="Top" Width="110" Value="50" Maximum="100" ValueChanged="sliderVolume_ValueChanged" />

        <Label Height="28" Margin="369,12,173,0" Name="label2" VerticalAlignment="Top">

            Rate:</Label>

        <Slider Height="23" HorizontalAlignment="Left" Margin="402,12,0,0" Maximum="5" Name="sliderRate" Value="3" VerticalAlignment="Top" Width="110" ValueChanged="sliderRate_ValueChanged" />

        <Button Height="23" HorizontalAlignment="Right" Margin="0,0,12,8"

                Name="ButtonSpeak" VerticalAlignment="Bottom" Width="101" Click="ButtonSpeak_Click">

            Speak

        </Button>

        <RichTextBox Margin="54,106,0,37" Name="richTextBox1"  />

        <Button Height="23" HorizontalAlignment="Left" Margin="351,77,0,0"

                Name="OpenTextFileButton" VerticalAlignment="Top" Width="110" Click="OpenTextFileButton_Click">

            Open a Text File

        </Button>

        <TextBox Height="23" Margin="54,77,0,0" Name="FileNameTextBox" VerticalAlignment="Top"

                 HorizontalAlignment="Left" Width="299" />

        <Label Content="(Open text file or type text in textbox)" HorizontalAlignment="Left" Margin="12,54,0,0" Name="label4" VerticalAlignment="Top" />

        <Label Height="28" HorizontalAlignment="Left" Margin="266,330,0,0" Name="labelProgress" VerticalAlignment="Top" />

        <Label Content="Text:" Height="28" HorizontalAlignment="Left" Margin="12,106,0,0" Name="label5" VerticalAlignment="Top" />

        <Label Content="File:" Height="28" HorizontalAlignment="Left" Margin="12,75,0,0" Name="label6" VerticalAlignment="Top" />

        <Label Height="28" HorizontalAlignment="Left" Margin="12,330,0,0" Name="labelState" VerticalAlignment="Top" />

    </Grid>

</Window>

Now let's start with the code

1. Add using directive
   
   using System.Speech.Synthesis;
   
   
2. Initialize SpeechSynthesizer object
   
   //speech synthesizer
   private SpeechSynthesizer synthesizer;
   
   
3. Add SpeechSynthesizer events on window load
   
   private void Window_Loaded(object sender, RoutedEventArgs e)
   {
       synthesizer = new SpeechSynthesizer();
       #region synthesizer eventes
       synthesizer.StateChanged += new EventHandler<StateChangedEventArgs>(synthesizer_StateChanged);
       synthesizer.SpeakStarted += new EventHandler<SpeakStartedEventArgs>(synthesizer_SpeakStarted);
       synthesizer.SpeakProgress += new EventHandler<SpeakProgressEventArgs>(synthesizer_SpeakProgress);
       synthesizer.SpeakCompleted += new EventHandler<SpeakCompletedEventArgs>(synthesizer_SpeakCompleted);
       #endregion
   }
   
   
4. Add event handlers 
   
   private void synthesizer_StateChanged(object sender, StateChangedEventArgs e)
   {
       //show the synthesizer's current state
       labelState.Content = e.State.ToString();
   }
   private void synthesizer_SpeakStarted(object sender, SpeakStartedEventArgs e)
   {
   }
   void synthesizer_SpeakProgress(object sender, SpeakProgressEventArgs e)
   {
       //show the synthesizer's current progress
       labelProgress.Content = e.Text;
   }
   private void synthesizer_SpeakCompleted(object sender, SpeakCompletedEventArgs e)
   {
       //reset when complete
       ButtonSpeak.Content = "Speak";
       labelProgress.Content = "";
   } 
   
   
5. And finally the buttonSpeak_click
   
   private void ButtonSpeak_Click(object sender, RoutedEventArgs e)
   {
       if (comboVoice.SelectedItem != null)
           synthesizer.SelectVoice(comboVoice.SelectedItem.ToString());
       synthesizer.Volume = Convert.ToInt32(sliderVolume.Value);
       synthesizer.Rate = Convert.ToInt32(sliderRate.Value);
       switch (synthesizer.State)
       {
           //if synthesizer is ready
           case SynthesizerState.Ready:
               synthesizer.SpeakAsync(ConvertRichTextBoxContentsToString());
               ButtonSpeak.Content = "Pause";
               break;
           //if synthesizer is paused
           case SynthesizerState.Paused:
               synthesizer.Resume();
               ButtonSpeak.Content = "Pause";
               break;
           //if synthesizer is speaking
           case SynthesizerState.Speaking:
               synthesizer.Pause();
               ButtonSpeak.Content = "Resume";
               break;
       }
   }

The resulting screen of the application will be as-