How to select an item in combobox in F# for UI automation

Question

invalid operation at

let pattern : SelectionPattern = LoginNameComboBox.GetCachedPattern(SelectionPattern.Pattern) :?> SelectionPattern <- error when run

let LoginNameComboBox : AutomationElement = LoginWin.FindFirst(TreeScope.Children, new PropertyCondition(AutomationElement.AutomationIdProperty, "cboUserID"));
if LoginNameComboBox = null then
    Console.WriteLine("No LoginNameComboBox")
else
    Console.WriteLine("Got LoginNameComboBox")
let pattern : SelectionPattern = LoginNameComboBox.GetCachedPattern(SelectionPattern.Pattern) :?> SelectionPattern <- error when run
let selectedItems = pattern.Cached.GetSelection();
let selectedItem = selectedItems.[0]

Answer 1

What kind of runtime exception do you have there?

I suppose that casting operator gives you an error, so maybe you should cast to different pattern (ex. SelectionItemPattern etc.) I think you can find out real object type in debugger.

---

Petr

Answer 2

do not know why null reference error

http://stackoverflow.com/questions/5814779/selecting-combobox-item-using-ui-automation

let GetSpecifiedPattern(element : AutomationElement, patternName : string) : AutomationPattern =
    let supportedPattern = element.GetSupportedPatterns() <--- error
    let mutable p : AutomationPattern = null
    for pattern in supportedPattern do
        if pattern.ProgrammaticName = patternName then
            p <- pattern
    p
let SetSelectedComboBoxItem(comboBox : AutomationElement, item : string) =
    let automationPatternFromElement : AutomationPattern = GetSpecifiedPattern(comboBox, "ExpandCollapsePatternIdentifiers.Pattern")
    let expandCollapsePattern : ExpandCollapsePattern = comboBox.GetCurrentPattern(automationPatternFromElement) :?> ExpandCollapsePattern
    expandCollapsePattern.Expand()
    expandCollapsePattern.Collapse()
    let listItem : AutomationElement = comboBox.FindFirst(TreeScope.Subtree, new PropertyCondition(AutomationElement.NameProperty, item))         
    automationPatternFromElement = GetSpecifiedPattern(listItem, "SelectionItemPatternIdentifiers.Pattern")
    let selectionItemPattern : SelectionItemPattern = listItem.GetCurrentPattern(automationPatternFromElement) :?> SelectionItemPattern
    selectionItemPattern.Select()
let process = Process.Start("..\\..\\..\\FinancialReportWPF\\bin\\Release\\FinancialReportWPF.exe")
let processId = process.Id;
let Desktop : AutomationElement = AutomationElement.RootElement
if Desktop = null then
    Console.WriteLine("Unable to get Desktop")
else
    Console.WriteLine("Found Desktop\n")
   
let mutable numWaits = 0;
let mutable LoginWin : AutomationElement = null
while LoginWin = null && numWaits < 50 do 
    Console.WriteLine("Looking for Login window. . . ")
    LoginWin <- Desktop.FindFirst(TreeScope.Children, new PropertyCondition(AutomationElement.NameProperty, "Test Financial Reporting"));
    numWaits <- numWaits + 1
    Thread.Sleep(200)
if LoginWin = null then
    Console.WriteLine("Failed to find Login window")
else
    Console.WriteLine("Found Login window")
    
let LoginNameComboBox : AutomationElement = LoginWin.FindFirst(TreeScope.Children, new PropertyCondition(AutomationElement.AutomationIdProperty, "cboUserID"));
if LoginNameComboBox = null then
    Console.WriteLine("No LoginNameComboBox")
else
    Console.WriteLine("Got LoginNameComboBox")
SetSelectedComboBoxItem(LoginNameComboBox, "MASTER")

Answer 3

Well, from your listing it seems that your 'LoginNameComboBox' is null. Do you have any output in Console window?

---

Petr

Answer 4

Console said got all the controls

AutomationElement.NameProperty <- error said this is null result in element  null in the following function

let GetSpecifiedPattern(element : AutomationElement, patternName : string) : AutomationPattern =

// Learn more about F# at http://fsharp.net
open System.Windows.Automation
open System.Diagnostics
open System.Threading
open System
(*    
let FindWindowByProcessId(processId : int) : AutomationElement =
    let targetWindow : AutomationElement= null
    let mutable count = 0;
    let p : Process = Process.GetProcessById(processId);
    let targetWindow = AutomationElement.FromHandle(p.MainWindowHandle);
    targetWindow
//let FindElementById(processId : int, automationId : string) : AutomationElement =
    //let aeForm : AutomationElement = FindWindowByProcessId(processId)
let FindElementById(processId : AutomationElement, automationId : string) : AutomationElement =
    let aeForm : AutomationElement = processId
    let tarFindElement : AutomationElement = aeForm.FindFirst(TreeScope.Descendants,
    new PropertyCondition(AutomationElement.AutomationIdProperty, automationId))
    tarFindElement
let GetSelectionItemPattern(element : AutomationElement) : SelectionItemPattern =
    let mutable currentPattern : obj = null
    //p./ProgrammaticName <- "MASTER"
    if element.TryGetCurrentPattern(SelectionItemPattern.Pattern, &currentPattern) = false then
        Console.WriteLine("Element with AutomationId '{0}' and Name '{1}' does not support the SelectionItemPattern.",
            element.Current.AutomationId, element.Current.Name);
    currentPattern :?> SelectionItemPattern
*)
let GetSpecifiedPattern(element : AutomationElement, patternName : string) : AutomationPattern =
    let supportedPattern = element.GetSupportedPatterns()
    let mutable p : AutomationPattern = null
    for pattern in supportedPattern do
        if pattern.ProgrammaticName = patternName then
            p <- pattern
    p
let SetSelectedComboBoxItem(comboBox : AutomationElement, item : string) =
    let automationPatternFromElement : AutomationPattern = GetSpecifiedPattern(comboBox, "ExpandCollapsePatternIdentifiers.Pattern")
    let expandCollapsePattern : ExpandCollapsePattern = comboBox.GetCurrentPattern(automationPatternFromElement) :?> ExpandCollapsePattern
    expandCollapsePattern.Expand()
    expandCollapsePattern.Collapse()
    let listItem : AutomationElement = comboBox.FindFirst(TreeScope.Subtree, new PropertyCondition(AutomationElement.NameProperty, item))         
    automationPatternFromElement = GetSpecifiedPattern(listItem, "SelectionItemPatternIdentifiers.Pattern")
    let selectionItemPattern : SelectionItemPattern = listItem.GetCurrentPattern(automationPatternFromElement) :?> SelectionItemPattern
    selectionItemPattern.Select()
let process = Process.Start("..\\..\\..\\FinancialReportWPF\\bin\\Release\\FinancialReportWPF.exe")
let processId = process.Id;
let Desktop : AutomationElement = AutomationElement.RootElement
if Desktop = null then
    Console.WriteLine("Unable to get Desktop")
else
    Console.WriteLine("Found Desktop\n")
   
let mutable numWaits = 0;
let mutable LoginWin : AutomationElement = null
while LoginWin = null && numWaits < 50 do 
    Console.WriteLine("Looking for Login window. . . ")
    LoginWin <- Desktop.FindFirst(TreeScope.Children, new PropertyCondition(AutomationElement.NameProperty, "Test Financial Reporting"));
    numWaits <- numWaits + 1
    Thread.Sleep(200)
if LoginWin = null then
    Console.WriteLine("Failed to find Login window")
else
    Console.WriteLine("Found Login window")
    
let mutable LoginButton = LoginWin.FindFirst(TreeScope.Children, new PropertyCondition(AutomationElement.NameProperty, "Login"))
if  LoginButton = null then
    Console.WriteLine("No LoginButton");
else
    Console.WriteLine("Got LoginButton");
    
let mutable QuitButton = LoginWin.FindFirst(TreeScope.Children, new PropertyCondition(AutomationElement.NameProperty, "Quit"))
if  QuitButton = null then
    Console.WriteLine("No QuitButton");
else
    Console.WriteLine("Got QuitButton");
    
let LoginNameComboBox : AutomationElement = LoginWin.FindFirst(TreeScope.Children, new PropertyCondition(AutomationElement.AutomationIdProperty, "cboUserID"));
if LoginNameComboBox = null then
    Console.WriteLine("No LoginNameComboBox")
else
    Console.WriteLine("Got LoginNameComboBox")
    
let PasswordTextBox : AutomationElement = LoginWin.FindFirst(TreeScope.Children, new PropertyCondition(AutomationElement.AutomationIdProperty, "txtPassword"));
if PasswordTextBox = null then
    Console.WriteLine("No txtPassword")
else
    Console.WriteLine("Got txtPassword")
let vpLoginTextBox : ValuePattern = PasswordTextBox.GetCurrentPattern(ValuePattern.Pattern) :?> ValuePattern
vpLoginTextBox.SetValue("testtest")
//let element : AutomationElement = FindElementById(processId, "cboUserID")
SetSelectedComboBoxItem(LoginNameComboBox, "MASTER")
//let element : AutomationElement = FindElementById(LoginNameComboBox, "5")
//let selectionItemPattern : SelectionItemPattern = GetSelectionItemPattern(element)
//selectionItemPattern.Select()
//selectionItemPattern.Select()
(*
// Set up the CacheRequest.
let comboCacheRequest = new CacheRequest()
comboCacheRequest.Add(SelectionPattern.Pattern)
comboCacheRequest.Add(SelectionPattern.SelectionProperty)
comboCacheRequest.Add(AutomationElement.NameProperty)
comboCacheRequest.TreeScope <- TreeScope.Element // TreeScope.Descendants;
// Activate the CacheRequest and get the element.
//use comboCacheRequest.Activate()
// Load the combo box element and cache the specified properties and patterns.
let propCondition : PropertyCondition = new PropertyCondition(AutomationElement.AutomationIdProperty, "cboUserID", PropertyConditionFlags.IgnoreCase)
let mutable elementCombo = LoginWin.FindFirst(TreeScope.Descendants, propCondition);
let propCondition1 : PropertyCondition = new PropertyCondition(AutomationElement.ControlTypeProperty, ControlType.List)
let listElement : AutomationElement = elementCombo.FindFirst(TreeScope.Children, propCondition1);
*)
// Register for ElementSelectedEvent on list items.
(*
if listElement <> null then
    Automation.AddAutomationEventHandler(SelectionItemPattern.ElementSelectedEvent, listElement,
        TreeScope.Children, selectHandler = new AutomationEventHandler(OnListItemSelect))
else7
    Console.WriteLine("No listElement")
*)
//let pattern : SelectionPattern = LoginNameComboBox.GetCachedPattern(SelectionPattern.Pattern) :?> SelectionPattern
//let selectedItems = pattern.Cached.GetSelection();
//let selectedItem = selectedItems.[1]
//let ipClickLoginButton : InvokePattern =(InvokePattern)LoginButton.GetCurrentPattern(InvokePattern.Pattern);
//ipClickLoginButton.Invoke();
//Thread.Sleep(1500)
(*
let ipClickQuitButton : InvokePattern = QuitButton.GetCurrentPattern(InvokePattern.Pattern) :?> InvokePattern
ipClickQuitButton.Invoke();
Thread.Sleep(1500)
*)
Console.ReadKey()