ShellTreeView.RefreshItem null reference exception

[tmedanovic]

Something odd is happening randomly when running an app using ShellTreeView:

Null reference happens when

ShellItem folder = (ShellItem) node.Tag;

is acessed in RefreshItem(TreeNode node) because it's null

What is really strange is that second argument of FindItem(e.Item.Parent, m_TreeView.Nodes[0]); m_TreeView.Nodes[0] is different when calling method and when passed to FindItem as you can see on the pictures below.

Another this that I don't understand is how is parent returned from FindItem if first arg is null and second doesn't have any nodes, really strange.

Here is details on few objects during debugging:

void m_ShellListener_ItemUpdated(object sender, ShellItemEventArgs e) e.Item {shell:///Desktop} ComInterface: COM Object DisplayName: "Desktop" FileSystemPath: "C:\Users\username\Desktop" HasSubFolders: true IsFileSystem: true IsFileSystemAncestor: true IsFolder: true IsReadOnly: false m_ComInterface: COM Object Parent: null ParsingName: "C:\Users\username\Desktop" Pidl: 83534968 ShellIcon: {(Icon)} ToolTipText: ""

m_TreeView.Nodes[0] {Text = "This PC"} base: {Text = "This PC"} BackColor: "{Name=0, ARGB=(0, 0, 0, 0)}" Bounds: {X = 22 Y = -108 Width = 44 Height = 18} Checked: false ContextMenu: null ContextMenuStrip: null FirstNode: {Text = "Desktop"} ForeColor: "{Name=0, ARGB=(0, 0, 0, 0)}" FullPath: "This PC" Handle: 83754648 ImageIndex: -1 ImageKey: "" Index: 0 IsEditing: false IsExpanded: true IsSelected: false IsVisible: false LastNode: {Text = "DVD RW Drive (F:)"} Level: 0 Name: "" NextNode: null NextVisibleNode: {Text = "Desktop"} NodeFont: null Nodes: {System.Windows.Forms.TreeNodeCollection} Parent: null PrevNode: null PrevVisibleNode: null SelectedImageIndex: -1 SelectedImageKey: "" StateImageIndex: -1 StateImageKey: "" Tag: {shell:///MyComputerFolder} Text: "This PC" ToolTipText: "" TreeView: {System.Windows.Forms.TreeView, Nodes.Count: 1, Nodes[0]: TreeNode: This PC}

parent {Text = ""} base: {Text = ""} BackColor: "{Name=0, ARGB=(0, 0, 0, 0)}" Bounds: {X = 0 Y = 0 Width = 0 Height = 0} Checked: false ContextMenu: null ContextMenuStrip: null FirstNode: null ForeColor: "{Name=0, ARGB=(0, 0, 0, 0)}" FullPath: "This PC\Desktop" Handle: 83752416 ImageIndex: -1 ImageKey: "" Index: 0 IsEditing: false IsExpanded: false IsSelected: false IsVisible: false LastNode: null Level: 2 Name: "" NextNode: null NextVisibleNode: {Text = "Documents"} NodeFont: null Nodes: {System.Windows.Forms.TreeNodeCollection} Parent: {Text = "Desktop"} PrevNode: null PrevVisibleNode: {Text = "This PC"} SelectedImageIndex: -1 SelectedImageKey: "" StateImageIndex: -1 StateImageKey: "" Tag: null Text: "" ToolTipText: "" TreeView: {System.Windows.Forms.TreeView, Nodes.Count: 1, Nodes[0]: TreeNode: This PC}

TreeNode FindItem(ShellItem item, TreeNode parent) parent {Text = ""} base: {Text = ""} BackColor: "{Name=0, ARGB=(0, 0, 0, 0)}" Bounds: {X = 0 Y = 0 Width = 0 Height = 0} Checked: false ContextMenu: null ContextMenuStrip: null FirstNode: null ForeColor: "{Name=0, ARGB=(0, 0, 0, 0)}" FullPath: "This PC\Desktop" Handle: 83752416 ImageIndex: -1 ImageKey: "" Index: 0 IsEditing: false IsExpanded: false IsSelected: false IsVisible: false LastNode: null Level: 2 Name: "" NextNode: null NextVisibleNode: {Text = "Documents"} NodeFont: null Nodes: {System.Windows.Forms.TreeNodeCollection} Parent: {Text = "Desktop"} PrevNode: null PrevVisibleNode: {Text = "This PC"} SelectedImageIndex: -1 SelectedImageKey: "" StateImageIndex: -1 StateImageKey: "" Tag: null Text: "" ToolTipText: "" TreeView: {System.Windows.Forms.TreeView, Nodes.Count: 1, Nodes[0]: TreeNode: This PC}

[grokys]

Could you try to create a minimal repro that exhibits this behaviour? It's not something I've seen before.

[tmedanovic]

Well the thing is that I don't know what triggers it, it happens randomly, but I think that it happend everytime app was minimized and running for some time, then when you bring it up it crashes. I will try to catch it, create a repro, and post back here.

[tmedanovic]

I managed to reproduce it, I also tried it with clean build, here are steps:

1. Run the app with ShellView
2. Go to charms -> Settings -> Change PC settings -> OneDrive -> File storage -> Save documents to OneDrive by default

[grokys]

Ah! Indeed changing the OneDrive setting seems to trigger it.

I need to take a look in more depth as to what is causing it, but it's Friday night here now so it will be next week (and I might not have much time then as I'll be on on a business trip :( )

[tmedanovic]

No hurry, my browser is still in development :laughing: