TFS自定义活动正在报告TFS工作区已删除

我有一个自定义TFS活动，它返回当前工作区。我使用的代码在这篇文章中找到，并在这里复制

日志文件将传入的工作区显示为

Inputs 
    Workspace: 10_1_RQ-SRV-TFS-12r2;NT AUTHORITY\NETWORK SERVICE 

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如何解决此问题？

当GetDefaultWorkspace活动放在Initialize Environment活动之后但在Get Sources活动之前时，它显示已删除。在Get Sources活动之后，我将GetDefaultWorkspace移动到了，它成功了

    public InArgument<Workspace> Workspace { get; set; }

    // If your activity returns a value, derive from CodeActivity<TResult>
    // and return the value from the Execute method.
    protected override void Execute()
    {
        var workspace = _context.GetValue<Workspace>(Workspace);

Exception Message: The workspace 10_1_RQ-SRV-TFS-12r2;NETWORK SERVICE has been deleted. (type WorkspaceDeletedException) Exception Stack Trace: at Microsoft.TeamFoundation.VersionControl.Client.Workspace.PendEdit(String path) at RQTfsActivities.RQSetVersion.Execute() 

Inputs 
    Workspace: 10_1_RQ-SRV-TFS-12r2;NT AUTHORITY\NETWORK SERVICE