Change Value in DataSet

I’m using BOs in a BPM and need to change a value in a Dataset between objects. I’m assuming I can do this with C# code, but not sure of the syntax.

My dataset variable name is RMADispDataSet and I need to access the RMADisp.ReasonCode field.

Something like this?

 using(var UD05Svc = Ice.Assemblies.ServiceRenderer.GetService<Ice.Contracts.UD05SvcContract>())
              //get new row
               var ds = new Ice.Tablesets.UD05Tableset();
                UD05Svc.GetaNewUD05(ref ds);    
                //modify ds
                var newUD05Row = ds.UD05.FirstOrDefault();
                newUD05Row.Company = "JRF";
                newUD05Row.Key1 = DateTime.Now.ToString();
                newUD05Row.Key2 = "update_status";
                newUD05Row.Key3 = "";
                newUD05Row.Key4 = "";
                newUD05Row.Key5 = "";
                newUD05Row.Date01 = DateTime.Now;
                newUD05Row.Character01 = json;
                UD05Svc.Update(ref ds);

Or if returning a dataset, access the table:

var svc = Ice.Assemblies.ServiceRenderer.GetService<Erp.Contracts.QuoteSvcContract>();
var ds = svc.GetByID(QuoteNum);

ds.QuoteDtl[0].PartNum = PartNum;
svc.ChangePartNum(ref ds, false, "");

That got me on the right path. Since the dataset was already created as global BPM variable, all I needed to do was create one line.

RMADispDataSet.RMADisp[0].ReasonCode = “MYREASON”;