There is no Screen Reader in .NET or in Visual C# langauge itself. The screen can be however accessed as a Graphics object in your application, and then you can use some sort of OCR or OMR service to read the characters from the graphics or image you save. I can give you an example of how to get the screen shot, which would help you to get the screen's content onto a Bitmap, for saving as an Image.
Once done, you can use an OCR to read those characters as string and so on.
Read this
Saving a Screenshot Using C#, A.K.A "Console Monitor"[
^]. You can go and download this sample code for the Microsoft OCR libary from
MSDN Gallery[
^].
But if you still want to develop one, you should go and read the MSFT's Accessibility overview. They have a set of documents for you to get started in building an application that would provide you the the spoken results that appear on the screen. However, websites already include the accessibility features and
ARIA[
^] property is one of them.
http://msdn.microsoft.com/en-us/library/windows/desktop/bb735024.aspx[
^]