I make use of SourceCode.Workflow.Client.dll to get K2 Process Worklist. In K2 Process, I add a Process Datafield "DealerCode", and when start process, I set value for this field, then in the Worklist query function,  I want to Implement the function which filtered by ProcessData "DealerCode" to get the disired WorklistItem. But even the matching WorklistItem is exist, the returned Worklist is alway null.  So I worry about if it's a K2 bug.

 The sample code show in below:

WorklistCriteria crit = new WorklistCriteria();

//dealerCode is the function parameter
crit.AddFilterField(WCLogical.And,WCField.ProcessData,"DealerCode",WCCompare.Equal,dealerCode);

//OpenConnection method is a wrapped method 

this.OpenConnection();
Worklist oWorkList = this.oK2Connection.OpenWorklist(crit);

....