Cannot add new Workitems using TFS API

Question

Hi I am trying to add new workitems to the TFS repository using the API, but when I validate the workitem before it is saved, it returns an error. I previously got exceptions regarding the field definitions for a bug namely, Symptom, Steps to Reproduce and Triage. (Error code TF 26027). The code snippet is shown below: Can anyone tell me what's wrong here?

switch (workItemType)
        {
            case "Bug":
                {
                    workItem.Title = values["Title"].ToString();
                    workItem.State = values["State"].ToString();
                    workItem.Reason = values["Reason"].ToString();
                    workItem.Fields["Priority"].Value = values["Priority"].ToString();
                    workItem.Fields["Severity"].Value = values["Severity"].ToString();
                    //workItem.Fields["Triage"].Value = values["Triage"].ToString();
                    workItem.Fields["Assigned To"].Value = values["Assigned To"].ToString();
                    //workItem.Fields["Symptom"].Value = values["Symptom"].ToString();
                    //workItem.Fields["Steps to Reproduce"].Value = values["Steps to Reproduce"].ToString();

                    // Validate the Work Item fields.
                    ArrayList result = workItem.Validate();
                    // If any invalid fields are returned, report an error.
                    if (result.Count > 0)
                        MessageBox.Show("An Error occurred while adding the Bug to the repository.");
                    else
                        workItem.Save();
                }
                break;

Answer 1

To find the available field definitions, you can iterate over the collection (FieldDefinitions). The Name and ReferenceName properties are the values you can index by into the collection.