Text to Speech in WPF

James Tomar
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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">

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

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

Rate:</Label>

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

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

Speak

</Button>

<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" />

</Grid>

</Window>

Now let's start with the code

Add using directive

using System.Speech.Synthesis;
Initialize SpeechSynthesizer object

//speech synthesizer
private SpeechSynthesizer synthesizer;
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
}
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 = "";
}
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;
   }
}