I just installed the Microsoft speech SDK 11 and added 2 different Runtime languages for english and chinese.
English seems to run fine, though chinese throws me this error
System.InvalidOperationException
with additional information
Speak error '80004005'
for the line
synth.Speak(s);
in the following code
using System;
using Microsoft.Speech.Synthesis;
namespace SampleSynthesis
{
    class Program
    {
        static void Main(string[] args)
        {
            speakString(0, "Hello, I'm TTS.");
        }
        static void speakString(int i, String s)
        {
            // Initialize a new instance of the SpeechSynthesizer.
            SpeechSynthesizer synth = new SpeechSynthesizer();
            // Select a voice. 
            switch (i)
            {
                case 0:
                    synth.SelectVoice("Microsoft Server Speech Text to Speech Voice (en-US, ZiraPro)");
                    break;
                case 1:
                    synth.SelectVoice("Microsoft Server Speech Text to Speech Voice (zh-CN, HuiHui)");
                    break;
            }
            // Configure the audio output. 
            synth.SetOutputToWaveFile(@"C:\Users\David\Desktop\TTStest\test.wav");
            synth.Speak(s);
        }
    }
}
In another question I found this answer, which states that there are crucial files missing in (since?) windows 8.1, but doesn't state any method for how to acquire these.
I am currently using a 64bit version of windows 10.
EDIT: I downloaded the files chsbrkr.dll and chtbrkr.dll and get the following new error
An unhandled exception of type 'System.InvalidCastException' occurred in Microsoft.Speech.dll
again for the same line in my code.