Error 'Value cannot be null:nodeName' when creating new iteration - api

Question

I'm getting an error when attempting to create a new Iteration using the Client SDK:
Value cannot be null.
Parameter name: nodeName
As a test, I tried creating it using Postman and the REST API—as suggested here—and it succeeded.
I've been using this successfully for quite a while now to stub out my sprint hierarchy for the year. This is the first such occurrence of this error—past year runs have gone off without a hitch. I haven't changed anything (that I know of) since last year's successful run.
As we can see, the iteration's Name property is being properly set. I tried Overloads instead of Shadows, but that didn't help.
How can I troubleshoot this to find out what nodeName is and how to populate it using the Client SDK?
Here's my code:
Module Main()
Private Sub AddYear(Year As Integer, Client As WorkItemTrackingHttpClient)
Dim oIterationYear As Classifications.Iteration
Dim dFinishDate As Date
Dim dStartDate As Date
Console.WriteLine($"Year:{vbTab}{vbTab}{Year}")
dFinishDate = New Date(Year, 12, 31)
dStartDate = New Date(Year, 1, 1)
oIterationYear = New Classifications.Iteration(Client, TeamProject, Year, dStartDate, dFinishDate)
oIterationYear.Save()
...
End Sub
End Module
Public Class Iteration
Inherits Base
Public Sub New(Client As WorkItemTrackingHttpClient, TeamProject As TeamProjects, Name As String, StartDate As Date, FinishDate As Date)
Me.New(Client, TeamProject, Name, StartDate, FinishDate, Nothing)
End Sub
Public Sub New(Client As WorkItemTrackingHttpClient, TeamProject As TeamProjects, Name As String, StartDate As Date, FinishDate As Date, Parent As Iteration)
MyBase.New(Client, TeamProject, Parent)
Me.StructureType = TreeNodeStructureType.Iteration
Me.FinishDate = FinishDate
Me.StartDate = StartDate
Me.Name = Name
End Sub
...
End Class
Public MustInherit Class Base
Inherits WorkItemClassificationNode
Public Sub New(Client As WorkItemTrackingHttpClient, TeamProject As TeamProjects, Parent As Base)
Me.ProjectName = TeamProject.ToDescription
Me.Parent = Parent
Me.Client = Client
End Sub
Public Sub Save()
If Me.Parent.IsNothing Then
Me.Node = Me.Client.CreateOrUpdateClassificationNodeAsync(Me, Me.ProjectName, Me.StructureType).Result <-- Error
Else
Me.Node = Me.Client.CreateOrUpdateClassificationNodeAsync(Me, Me.ProjectName, Me.StructureType, path:=Me.Path).Result
End If
End Sub
...
Public Shadows Property Name As String
Get
If Me.Node.IsNothing Then
Name = Me._Name
Else
Name = Me.Node.Name
End If
End Get
Set(Value As String)
Me._Name = Value
End Set
End Property
Private _Name As String
End Class
Note: this is a language-agnostic question, thus I've intentionally omitted the VB.NET tag. An answer can come in either VB.NET or C#—I'm fine with either one.
-- EDIT --
Based on the design suggestions found in the accepted answer, I've come up with this solution that works:
Public MustInherit Class Base
Public Sub New(Client As WorkItemTrackingHttpClient, TeamProject As TeamProjects, Parent As Base)
Me.Node = New WorkItemClassificationNode With {
.StructureType = StructureType,
.Name = Name
}
Me.ProjectName = TeamProject.ToDescription
Me.Parent = Parent
Me.Client = Client
Me.Name = Name
End Sub
Public Sub Save()
If Me.Parent.IsNothing Then
Me.Node = Me.Client.CreateOrUpdateClassificationNodeAsync(Me.Node, Me.ProjectName, Me.StructureType).Result
Else
Me.Node = Me.Client.CreateOrUpdateClassificationNodeAsync(Me.Node, Me.ProjectName, Me.StructureType, path:=Me.Path).Result
End If
End Sub
...
Public Property Name As String
Get
Return Me.Node.Name
End Get
Private Set(Value As String)
Me.Node.Name = Value
End Set
End Property
End Class
Essentially all I did was remove the base class' inheritance from WorkItemClassificationNode and store a node reference internally in all cases. I also simplified the Name property implementation.
As for why it suddenly stopped working with no change in my code, the only thing I can think of is the remote possibility that there was a change in the compiler that affected how the SDK evaluates the Shadows and Overloads keywords. That's a long shot, I know, but I'm at a complete loss otherwise.
Bottom line, it works now.

Answer 1

I can create new iteration using Microsoft.TeamFoundation.WorkItemTracking.WebApi in Azure DevOps Services .NET SDK.
Please check out below example:
class Program
{
static void Main(string[] args)
{
Uri accountUri = new Uri("https://dev.azure.com/org/");
string personalAccessToken = "pat";
VssConnection _connection = new VssConnection(accountUri, new VssBasicCredential(string.Empty, personalAccessToken));
WorkItemTrackingHttpClient workItemTrackingHttpClient = _connection.GetClient<WorkItemTrackingHttpClient>();
Iteration iteration = new Iteration(workItemTrackingHttpClient,2021, "projectName");
iteration.SaveNode();
}
}
public class Iteration
{
WorkItemTrackingHttpClient client;
WorkItemClassificationNode node;
string project;
string path;
public Iteration(WorkItemTrackingHttpClient client, int Year, string project, string path=null) {
this.client = client;
node = new WorkItemClassificationNode();
this.project = project;
this.path = path;
IDictionary<string, object> DateAttr = new Dictionary<string, object>();
DateAttr.Add("startDate", new DateTime(Year, 1, 1));
DateAttr.Add("finishDate", new DateTime(Year, 12, 31));
node.Attributes = DateAttr;
node.Name = Year.ToString();
node.StructureType = TreeNodeStructureType.Iteration;
}
public void SaveNode()
{
var res = client.CreateOrUpdateClassificationNodeAsync(node, project, TreeStructureGroup.Iterations, path).Result;
Console.WriteLine(res.Id);
}
}
See below result:
I can reproduce above error Value cannot be null. Parameter name: nodeName. If i intentionally didnot set the node.Name = null; You can debug your code to check why the node name was not set.