Oftentimes jqGrid is used in ASP.NET or MVC web app. Sometimes it is also the case that a .NET based web service provides data for jqGrid.
jqGrid reads JSON data the faster than data in any other format. JSON is not native to the .NET world, though, XML is.
Codemerx JSON Serializer for jqGrid steps in to bridge that gap. It comes as a small, well-documented MS Visual Studio C# project that could easily be integrated in your solution. Also, it is free and it comes under the MIT License that provides maximum flexibility of use.