Google Text-To-Speech API

Old answer:

Try using this URL:
http://translate.google.com/translate_tts?tl=en&q=Hello%20World
It will automatically generate a wav file which you can easily get with an HTTP request through any .net programming.

Edit:

Ohh Google, you thought you could prevent people from using your wonderful service with flimsy http header verification.

Here is a solution to get a response in multiple languages (I’ll try to add more as we go):

NodeJS

// npm install `request`
const fs = require('fs');
const request = require('request');
const text="Hello World";

const options = {
    url: `https://translate.google.com/translate_tts?ie=UTF-8&q=${encodeURIComponent(text)}&tl=en&client=tw-ob`,
    headers: {
        'Referer': 'http://translate.google.com/',
        'User-Agent': 'stagefright/1.2 (Linux;Android 5.0)'
    }
}

request(options)
    .pipe(fs.createWriteStream('tts.mp3'))

---

Curl

curl 'https://translate.google.com/translate_tts?ie=UTF-8&q=Hello%20Everyone&tl=en&client=tw-ob' -H 'Referer: http://translate.google.com/' -H 'User-Agent: stagefright/1.2 (Linux;Android 5.0)' > google_tts.mp3

Note that the headers are based on @Chris Cirefice’s example, if they stop working at some point I’ll attempt to recreate conditions for this code to function. All credits for the current headers go to him and the wonderful tool that is WireShark. (also thanks to Google for not patching this)