at com.shephertz.app42.paas.sdk.csharp.util.Util.ThrowExceptionIfNullOrBlank

Question

I call this function but data could not inserted into storage and get exception 

 " at com.shephertz.app42.paas.sdk.csharp.util.Util.ThrowExceptionIfNullOrBlank (System.Object param, System.String paramName) [0x00000] in <filename unknown>:0 "

 

public void InsertDocument()
        {
            
            JSONClass json = new JSONClass();
            json.Add ("testkey" , "key");
            storageService.InsertJSONDocument (dbName, collectionName, json, new Callback ());
            print ("call back");
        }