The .NET Framework is the easiest way to build apps on the Microsoft platform. You can download Visual Studio Express for free, and be coding in just a few minutes. You can also use the .NET SDKs and targeting packs to build apps for a given Microsoft platform, such as Windows Azure.
AT&T Developer Program Expose AT&T APIs like Speech, SMS, and MMS through the AT&T API SDKs for Windows. Use the sample code, source code, and intrinsic features to quickly build and release C# and Visual Basic applications to market.