I have a column grouped by groupname of producttype having values likes diesel,electric,gas,petrol but i want specific order in groups to appear like diesel,petrol,electric,gas 

Using  

Protected void onstateinithandler(gridstateeventargs <prdouctmodel> args)

{

gridstate <productmodel> statetobe = new gridstate <productmodel>()

{

GroupDescriptors = new list <groupdescriptor>()

{

new GroupDescriptor()

{ Member= "producttype",

Membertype =typeof (string)

}

},

Collapsedgroups =enumerable.range (0,4).tolist ()

};

args.gridstate = statetobe

}