“SDR# (read SDR Sharp) is a simple, intuitive, small and fast PC-based DSP application for Software Defined Radio. It’s written in C# with both object design correctness and performance in mind. The main purpose is to offer a simple proof of concept application to get hands into DSP techniques. It supports SoftRock, FiFiSDR, FUNcube Dongle, SDR-4 [,rtl-sdr] and any sound card based SDR front end.” — SDRSharp.com
SDR# (SDR-Sharp) versions 244+ (dev) have added support for RTL based SDRs supported by ExtIO. Extract the download link to the same folder you installed ExtIO to. If you haven’t done that yet, try this guide.
To use the software with an RTLSDR dongle, Select USRP under the ‘Front End’ drop down box beside the Front End button. Then use the now active ‘Front End’ button to show the ExtIO GUI. Don’t forget to add your device hint!