I don't recommend you to use datatype as function if it is not really required. In very old version of jqGrid (more as one year old) was less support for different options of ajax requests. Since at least more then one year you can use new options (see here

From the performance side the best choice will be to has a WCF service published in the same web side. You can find the example here. The second choice will be an ASMX web service (see here). All this solutions you can easy integrate as a part of the ASP.NET Web Form site. It will work for pure HTML pages also. To edit jqGrid data see this. This one

Sorry jdege,

but I don't agree with your statements about the complexity. If you rename one file so that it has just correct extension ASMX, you code

[WebMethod()]
[ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public static MyData getMyData(Dictionary postData)
{


editurl as a function is not supported. You should use 'clientArray' in case of inline editing. Form editing had not full support of local editing. Probably now?