text to speech in c#

First, we need to reference the System.Speech assembly from the application. From the Project menu, choose Add Reference. The from the .NET tab, highlight System.Speech and choose OK.

Declarations

Next, we need to declare and instantiate a speech object. The class isSystem.Speech.Synthesis.Speechsynthesizer. This one class has enough properties and methods to speak a string using the default language and voice of the OS. In Microsoft Windows Vista, the default voice is Microsoft Ana. 

protected void ibtnSpeaker_Click(object sender, ImageClickEventArgs e)
        {
            Thread t = new Thread(() =>
            {
                SpeechSynthesizer audio = new SpeechSynthesizer();
                audio.SelectVoiceByHints(VoiceGender.Female, VoiceAge.Senior); // to change VoiceGender and VoiceAge check out those links below
                audio.Volume = 100;  // (0 - 100)
                audio.Rate = -1;     // (-10 - 10)
                audio.Speak(lblQuestionStart.Text);
            });
            t.Start();
        }