Can't use Expand and Collapse methods or patterns on TreeItems using FlaUI in C#?

Question

I'm trying to define a function that expands or collapses a given TreeItem by a target state using FlaUI for testing a program in C#.

I'm able to find the element, but I can't access any information or methods for expanding and collapsing TreeItem elements. I get the following error when trying to set the currentPattern variable. I was also not able to just run the Expand and Collapse methods on the TreeItem.

Error: FlaUI.Core.Exceptions.PatternNotSupportedException: 'The requested pattern 'ExpandCollapse [#10005]' is not supported'

The function I have written is:

public TreeItem ToggleTreeNode(string inNodeName, ExpandCollapseState inTargetState, AutomationElement inParentNode = null)
{
    TreeItem nodeElement = null; //TreeItem nodeElement = null;
    if (inParentNode == null)
    {
        nodeElement = mSTGOCMainForm.FindFirstDescendant(cf => cf.ByName(inNodeName)).AsTreeItem();
    }
    else
    {
        nodeElement = inParentNode.FindFirstDescendant(cf => cf.ByName(inNodeName)).AsTreeItem();
    }
    
    // Collapse or Expand
    var currentPattern = nodeElement.Patterns.ExpandCollapse.Pattern;
    var currentState = currentPattern.ExpandCollapseState.Value;

    if (inTargetState != currentState)
    {
        //Then do the operation
        if (inTargetState == ExpandCollapseState.Collapsed)
        {
            nodeElement.Collapse();
        }
        else if (inTargetState == ExpandCollapseState.Expanded)
        {
            nodeElement.Expand();
        }
    }

    return nodeElement;
}

I'm using FlaUI.Core and FlaUI.UIA2, version 3.2.0.

Answer 1

It seems that your TreeItems just don't support the UIA Collapse/Expand pattern. Either there is a nested or parent element that supports the pattern (check with any inspect tool) or you need to use keyboard or mouse to collapse/expand.

Answer 2

I had the same error when I found a button on my TreeItem. The button had an automation ID, but the TreeItem did not. To use Expand(), I had to find the button and define my variable as the Parent. Note the .Parent.AsTreeItem() at the end.

TreeItem DiagnosticLogsTreeItem => Window.FindFirstDescendant(By.ByAutomationId("PageLink_Diagnostic Logs")).Parent.AsTreeItem();