嘗試返回文檔時出現對象錯誤（Umbraco Document API）

Question

我正在處理遞歸方法，該方法顯示我有權查看的所有文檔。第一遍的偉大工程，但是當它遞歸調用自己通過當前文檔的兒童的文件陣列，它拋出一個錯誤：

Object reference not set to an instance of an object. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

下面的代碼：

protected void Page_Load(object sender, EventArgs e) 
{ 
    lblTest.Text = "Data<br /><br />"; 
    Document[] releaseDocs = Document.GetRootDocuments(); 
    displayDocs(releaseDocs); 
} 
public void displayDocs(Document[] releaseDocs) 
{ 
    string docPermissions = null; 
    User currentUser = User.GetCurrent(); 
    foreach (var doc in releaseDocs) 
    { 
     docPermissions = currentUser.GetPermissions(doc.Path); 
     if ((docPermissions.Contains("F")) && (docPermissions.Contains("U"))) 
     { 
      lblTest.Text += "D/T: " + doc.CreateDateTime + "<br />\r\n"; 
      lblTest.Text += "Level: " + doc.Level + "<br />\r\n"; 
      lblTest.Text += "Text: " + doc.Text + "<br />\r\n"; 
      lblTest.Text += "<hr />\r\n"; 
      if (doc.HasChildren) 
      { 
       Document[] childDocs = Document.GetChildrenForTree(doc.Id); 
       displayDocs(childDocs); //error occurs here 
      } 
     } 
    } 
} 

Answer 1

難道文檔.GetChildrenForTree（doc.Id）方法返回null？