#### [PromptPlus](PromptPlus.md 'PromptPlus')
### [PromptPlusLibrary](PromptPlusLibrary.md 'PromptPlusLibrary')
## ITreeSelectControl\ Interface
Provides a fluent API for configuring and running the TreeSelect control, which browses an
arbitrary hierarchy of items of type [T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T') as an expandable/collapsible tree\.
```csharp
public interface ITreeSelectControl
```
#### Type parameters
`T`
The type of items in the tree\.
### Remarks
The tree structure is built explicitly by the caller through [Root\(T, bool\)](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.Root(T,bool) 'PromptPlusLibrary\.ITreeSelectControl\\.Root\(T, bool\)'),
[AddLast\(T, bool\)](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.AddLast(T,bool) 'PromptPlusLibrary\.ITreeSelectControl\\.AddLast\(T, bool\)')/[AddFirst\(T, bool\)](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.AddFirst(T,bool) 'PromptPlusLibrary\.ITreeSelectControl\\.AddFirst\(T, bool\)') \(first\-level nodes\),
[AddAfter\(ITreeNode<T>, T, bool\)](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.AddAfter(PromptPlusLibrary.ITreeNode_T_,T,bool) 'PromptPlusLibrary\.ITreeSelectControl\\.AddAfter\(PromptPlusLibrary\.ITreeNode\, T, bool\)')/[AddBefore\(ITreeNode<T>, T, bool\)](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.AddBefore(PromptPlusLibrary.ITreeNode_T_,T,bool) 'PromptPlusLibrary\.ITreeSelectControl\\.AddBefore\(PromptPlusLibrary\.ITreeNode\, T, bool\)')
\(sibling insertion\) and [AddLast\(T, bool\)](ITreeNode_T_.md#PromptPlusLibrary.ITreeNode_T_.AddLast(T,bool) 'PromptPlusLibrary\.ITreeNode\\.AddLast\(T, bool\)')/
[AddFirst\(T, bool\)](ITreeNode_T_.md#PromptPlusLibrary.ITreeNode_T_.AddFirst(T,bool) 'PromptPlusLibrary\.ITreeNode\\.AddFirst\(T, bool\)') \(nested children\)\. Whether a node is a
container or a leaf is inferred from whether it has children\. The rendered tree
materializes visible rows lazily on expand and releases them on collapse, keeping memory
proportional to what is visible\. Nodes can be marked `disable` at creation time so
they are shown and navigable but cannot be confirmed\.
### Methods
## ITreeSelectControl\\.AddAfter\(ITreeNode\, T, bool\) Method
Inserts a sibling immediately after [node](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.AddAfter(PromptPlusLibrary.ITreeNode_T_,T,bool).node 'PromptPlusLibrary\.ITreeSelectControl\\.AddAfter\(PromptPlusLibrary\.ITreeNode\, T, bool\)\.node')\.
```csharp
PromptPlusLibrary.ITreeNode AddAfter(PromptPlusLibrary.ITreeNode node, T value, bool disable=false);
```
#### Parameters
`node` [PromptPlusLibrary\.ITreeNode<](ITreeNode_T_.md 'PromptPlusLibrary\.ITreeNode\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeNode_T_.md 'PromptPlusLibrary\.ITreeNode\')
The reference sibling\. Cannot be `null`\.
`value` [T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')
The value of the new node\. Cannot be `null`\.
`disable` [System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')
When `true`, the new node cannot be confirmed\. Default is `false`\.
#### Returns
[PromptPlusLibrary\.ITreeNode<](ITreeNode_T_.md 'PromptPlusLibrary\.ITreeNode\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeNode_T_.md 'PromptPlusLibrary\.ITreeNode\')
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
When [node](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.AddAfter(PromptPlusLibrary.ITreeNode_T_,T,bool).node 'PromptPlusLibrary\.ITreeSelectControl\\.AddAfter\(PromptPlusLibrary\.ITreeNode\, T, bool\)\.node') is `null`\.
[System\.InvalidOperationException](https://learn.microsoft.com/en-us/dotnet/api/system.invalidoperationexception 'System\.InvalidOperationException')
When [node](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.AddAfter(PromptPlusLibrary.ITreeNode_T_,T,bool).node 'PromptPlusLibrary\.ITreeSelectControl\\.AddAfter\(PromptPlusLibrary\.ITreeNode\, T, bool\)\.node') does not belong to this tree\.
## ITreeSelectControl\\.AddBefore\(ITreeNode\, T, bool\) Method
Inserts a sibling immediately before [node](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.AddBefore(PromptPlusLibrary.ITreeNode_T_,T,bool).node 'PromptPlusLibrary\.ITreeSelectControl\\.AddBefore\(PromptPlusLibrary\.ITreeNode\, T, bool\)\.node')\.
```csharp
PromptPlusLibrary.ITreeNode AddBefore(PromptPlusLibrary.ITreeNode node, T value, bool disable=false);
```
#### Parameters
`node` [PromptPlusLibrary\.ITreeNode<](ITreeNode_T_.md 'PromptPlusLibrary\.ITreeNode\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeNode_T_.md 'PromptPlusLibrary\.ITreeNode\')
The reference sibling\. Cannot be `null`\.
`value` [T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')
The value of the new node\. Cannot be `null`\.
`disable` [System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')
When `true`, the new node cannot be confirmed\. Default is `false`\.
#### Returns
[PromptPlusLibrary\.ITreeNode<](ITreeNode_T_.md 'PromptPlusLibrary\.ITreeNode\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeNode_T_.md 'PromptPlusLibrary\.ITreeNode\')
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
When [node](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.AddBefore(PromptPlusLibrary.ITreeNode_T_,T,bool).node 'PromptPlusLibrary\.ITreeSelectControl\\.AddBefore\(PromptPlusLibrary\.ITreeNode\, T, bool\)\.node') is `null`\.
[System\.InvalidOperationException](https://learn.microsoft.com/en-us/dotnet/api/system.invalidoperationexception 'System\.InvalidOperationException')
When [node](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.AddBefore(PromptPlusLibrary.ITreeNode_T_,T,bool).node 'PromptPlusLibrary\.ITreeSelectControl\\.AddBefore\(PromptPlusLibrary\.ITreeNode\, T, bool\)\.node') does not belong to this tree\.
## ITreeSelectControl\\.AddFirst\(T, bool\) Method
Adds a first\-level node \(child of the root\) at the beginning\.
```csharp
PromptPlusLibrary.ITreeNode AddFirst(T value, bool disable=false);
```
#### Parameters
`value` [T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')
The value of the new node\. Cannot be `null`\.
`disable` [System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')
When `true`, the new node cannot be confirmed\. Default is `false`\.
#### Returns
[PromptPlusLibrary\.ITreeNode<](ITreeNode_T_.md 'PromptPlusLibrary\.ITreeNode\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeNode_T_.md 'PromptPlusLibrary\.ITreeNode\')
#### Exceptions
[System\.InvalidOperationException](https://learn.microsoft.com/en-us/dotnet/api/system.invalidoperationexception 'System\.InvalidOperationException')
When the root has not been set yet\.
## ITreeSelectControl\\.AddLast\(T, bool\) Method
Adds a first\-level node \(child of the root\) at the end\.
```csharp
PromptPlusLibrary.ITreeNode AddLast(T value, bool disable=false);
```
#### Parameters
`value` [T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')
The value of the new node\. Cannot be `null`\.
`disable` [System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')
When `true`, the new node cannot be confirmed\. Default is `false`\.
#### Returns
[PromptPlusLibrary\.ITreeNode<](ITreeNode_T_.md 'PromptPlusLibrary\.ITreeNode\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeNode_T_.md 'PromptPlusLibrary\.ITreeNode\')
The newly created node so children can be attached to it\.
#### Exceptions
[System\.InvalidOperationException](https://learn.microsoft.com/en-us/dotnet/api/system.invalidoperationexception 'System\.InvalidOperationException')
When the root has not been set yet\.
## ITreeSelectControl\\.ChangeDescription\(Func\\) Method
Dynamically updates the prompt description based on the currently selected node\.
```csharp
PromptPlusLibrary.ITreeSelectControl ChangeDescription(System.Func value);
```
#### Parameters
`value` [System\.Func<](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[,](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[System\.String](https://learn.microsoft.com/en-us/dotnet/api/system.string 'System\.String')[>](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')
A function that receives the current item and returns the description\. Cannot be `null`\.
#### Returns
[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
When [value](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.ChangeDescription(System.Func_T,string_).value 'PromptPlusLibrary\.ITreeSelectControl\\.ChangeDescription\(System\.Func\\)\.value') is `null`\.
## ITreeSelectControl\\.ChangeDescriptionAsync\(Func\\>\) Method
Asynchronous counterpart of [ChangeDescription\(Func<T,string>\)](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.ChangeDescription(System.Func_T,string_) 'PromptPlusLibrary\.ITreeSelectControl\\.ChangeDescription\(System\.Func\\)')\. The task is
awaited synchronously \(blocking\) each frame\.
```csharp
PromptPlusLibrary.ITreeSelectControl ChangeDescriptionAsync(System.Func> value);
```
#### Parameters
`value` [System\.Func<](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[,](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[System\.Threading\.Tasks\.Task<](https://learn.microsoft.com/en-us/dotnet/api/system.threading.tasks.task-1 'System\.Threading\.Tasks\.Task\`1')[System\.String](https://learn.microsoft.com/en-us/dotnet/api/system.string 'System\.String')[>](https://learn.microsoft.com/en-us/dotnet/api/system.threading.tasks.task-1 'System\.Threading\.Tasks\.Task\`1')[>](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')
#### Returns
[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
When [value](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.ChangeDescriptionAsync(System.Func_T,System.Threading.Tasks.Task_string__).value 'PromptPlusLibrary\.ITreeSelectControl\\.ChangeDescriptionAsync\(System\.Func\\>\)\.value') is `null`\.
## ITreeSelectControl\\.Default\(T, bool\) Method
Pre\-selects an item, expanding the tree down to it when reachable from the root\.
```csharp
PromptPlusLibrary.ITreeSelectControl Default(T value, bool useDefaultHistory=true);
```
#### Parameters
`value` [T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')
`useDefaultHistory` [System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')
#### Returns
[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
When [value](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.Default(T,bool).value 'PromptPlusLibrary\.ITreeSelectControl\\.Default\(T, bool\)\.value') is `null`\.
## ITreeSelectControl\\.DefaultMatchBy\(Func\\) Method
Sets the item comparator used to locate the default value and the value restored from
history within the tree\. Required\.
```csharp
PromptPlusLibrary.ITreeSelectControl DefaultMatchBy(System.Func comparer);
```
#### Parameters
`comparer` [System\.Func<](https://learn.microsoft.com/en-us/dotnet/api/system.func-3 'System\.Func\`3')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[,](https://learn.microsoft.com/en-us/dotnet/api/system.func-3 'System\.Func\`3')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[,](https://learn.microsoft.com/en-us/dotnet/api/system.func-3 'System\.Func\`3')[System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')[>](https://learn.microsoft.com/en-us/dotnet/api/system.func-3 'System\.Func\`3')
#### Returns
[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
When comparer is `null`\.
## ITreeSelectControl\\.EnableHistory\(string, Action\\) Method
Enables history: the selected value is serialized as JSON and stored, and on the next run
the tree is searched \(using [DefaultMatchBy\(Func<T,T,bool>\)](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.DefaultMatchBy(System.Func_T,T,bool_) 'PromptPlusLibrary\.ITreeSelectControl\\.DefaultMatchBy\(System\.Func\\)')\) for an item that equals the restored
value so that it can be pre\-selected\.
```csharp
PromptPlusLibrary.ITreeSelectControl EnableHistory(string filename, System.Action? options=null);
```
#### Parameters
`filename` [System\.String](https://learn.microsoft.com/en-us/dotnet/api/system.string 'System\.String')
`options` [System\.Action<](https://learn.microsoft.com/en-us/dotnet/api/system.action-1 'System\.Action\`1')[IHistoryOptions](IHistoryOptions.md 'PromptPlusLibrary\.IHistoryOptions')[>](https://learn.microsoft.com/en-us/dotnet/api/system.action-1 'System\.Action\`1')
#### Returns
[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
When [filename](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.EnableHistory(string,System.Action_PromptPlusLibrary.IHistoryOptions_).filename 'PromptPlusLibrary\.ITreeSelectControl\\.EnableHistory\(string, System\.Action\\)\.filename') is `null`\.
## ITreeSelectControl\\.ExtraInfo\(Func\\) Method
Sets an optional extra info selector rendered next to the node text\.
```csharp
PromptPlusLibrary.ITreeSelectControl ExtraInfo(System.Func extraInfoNode);
```
#### Parameters
`extraInfoNode` [System\.Func<](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[,](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[System\.String](https://learn.microsoft.com/en-us/dotnet/api/system.string 'System\.String')[>](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')
#### Returns
[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
When [extraInfoNode](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.ExtraInfo(System.Func_T,string_).extraInfoNode 'PromptPlusLibrary\.ITreeSelectControl\\.ExtraInfo\(System\.Func\\)\.extraInfoNode') is `null`\.
## ITreeSelectControl\\.ExtraInfoAsync\(Func\\>\) Method
Asynchronous counterpart of [ExtraInfo\(Func<T,string>\)](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.ExtraInfo(System.Func_T,string_) 'PromptPlusLibrary\.ITreeSelectControl\\.ExtraInfo\(System\.Func\\)')\.
The task is awaited synchronously \(blocking\) once per node, per render frame\.
```csharp
PromptPlusLibrary.ITreeSelectControl ExtraInfoAsync(System.Func> extraInfoNode);
```
#### Parameters
`extraInfoNode` [System\.Func<](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[,](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[System\.Threading\.Tasks\.Task<](https://learn.microsoft.com/en-us/dotnet/api/system.threading.tasks.task-1 'System\.Threading\.Tasks\.Task\`1')[System\.String](https://learn.microsoft.com/en-us/dotnet/api/system.string 'System\.String')[>](https://learn.microsoft.com/en-us/dotnet/api/system.threading.tasks.task-1 'System\.Threading\.Tasks\.Task\`1')[>](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')
#### Returns
[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
When [extraInfoNode](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.ExtraInfoAsync(System.Func_T,System.Threading.Tasks.Task_string__).extraInfoNode 'PromptPlusLibrary\.ITreeSelectControl\\.ExtraInfoAsync\(System\.Func\\>\)\.extraInfoNode') is `null`\.
## ITreeSelectControl\\.Filter\(FilterMode\) Method
Enables interactive filtering\. When the user types a printable character while the tree
is in select mode the control switches to filter mode, flattens the whole tree once and
applies the requested [FilterMode](FilterMode.md 'PromptPlusLibrary\.FilterMode') against the node full path \(parent chain
joined by [PathSeparator\(char\)](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.PathSeparator(char) 'PromptPlusLibrary\.ITreeSelectControl\\.PathSeparator\(char\)')\)\. Clearing the filter restores the lazy tree
view preserving the previous expand/collapse state\.
```csharp
PromptPlusLibrary.ITreeSelectControl Filter(PromptPlusLibrary.FilterMode value);
```
#### Parameters
`value` [FilterMode](FilterMode.md 'PromptPlusLibrary\.FilterMode')
The [FilterMode](FilterMode.md 'PromptPlusLibrary\.FilterMode') to apply\.
#### Returns
[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')
## ITreeSelectControl\\.Interaction\\(IEnumerable\, Action\\>\) Method
Iterates [items](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.Interaction_T1_(System.Collections.Generic.IEnumerable_T1_,System.Action_T1,PromptPlusLibrary.ITreeSelectControl_T__).items 'PromptPlusLibrary\.ITreeSelectControl\\.Interaction\\(System\.Collections\.Generic\.IEnumerable\, System\.Action\\>\)\.items') and invokes [interactionAction](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.Interaction_T1_(System.Collections.Generic.IEnumerable_T1_,System.Action_T1,PromptPlusLibrary.ITreeSelectControl_T__).interactionAction 'PromptPlusLibrary\.ITreeSelectControl\\.Interaction\\(System\.Collections\.Generic\.IEnumerable\, System\.Action\\>\)\.interactionAction') for each
element, giving the caller a chance to add first\-level nodes \(and further descendants\)
programmatically\. Equivalent to calling [AddLast\(T, bool\)](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.AddLast(T,bool) 'PromptPlusLibrary\.ITreeSelectControl\\.AddLast\(T, bool\)') inside the loop\.
```csharp
PromptPlusLibrary.ITreeSelectControl Interaction(System.Collections.Generic.IEnumerable items, System.Action> interactionAction);
```
#### Type parameters
`T1`
#### Parameters
`items` [System\.Collections\.Generic\.IEnumerable<](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.ienumerable-1 'System\.Collections\.Generic\.IEnumerable\`1')[T1](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.Interaction_T1_(System.Collections.Generic.IEnumerable_T1_,System.Action_T1,PromptPlusLibrary.ITreeSelectControl_T__).T1 'PromptPlusLibrary\.ITreeSelectControl\\.Interaction\\(System\.Collections\.Generic\.IEnumerable\, System\.Action\\>\)\.T1')[>](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.ienumerable-1 'System\.Collections\.Generic\.IEnumerable\`1')
`interactionAction` [System\.Action<](https://learn.microsoft.com/en-us/dotnet/api/system.action-2 'System\.Action\`2')[T1](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.Interaction_T1_(System.Collections.Generic.IEnumerable_T1_,System.Action_T1,PromptPlusLibrary.ITreeSelectControl_T__).T1 'PromptPlusLibrary\.ITreeSelectControl\\.Interaction\\(System\.Collections\.Generic\.IEnumerable\, System\.Action\\>\)\.T1')[,](https://learn.microsoft.com/en-us/dotnet/api/system.action-2 'System\.Action\`2')[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[>](https://learn.microsoft.com/en-us/dotnet/api/system.action-2 'System\.Action\`2')
#### Returns
[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
When [items](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.Interaction_T1_(System.Collections.Generic.IEnumerable_T1_,System.Action_T1,PromptPlusLibrary.ITreeSelectControl_T__).items 'PromptPlusLibrary\.ITreeSelectControl\\.Interaction\\(System\.Collections\.Generic\.IEnumerable\, System\.Action\\>\)\.items') or [interactionAction](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.Interaction_T1_(System.Collections.Generic.IEnumerable_T1_,System.Action_T1,PromptPlusLibrary.ITreeSelectControl_T__).interactionAction 'PromptPlusLibrary\.ITreeSelectControl\\.Interaction\\(System\.Collections\.Generic\.IEnumerable\, System\.Action\\>\)\.interactionAction') is `null`\.
## ITreeSelectControl\\.InteractionAsync\\(IEnumerable\, Func\,Task\>\) Method
Asynchronous counterpart of [Interaction<T1>\(IEnumerable<T1>, Action<T1,ITreeSelectControl<T>>\)](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.Interaction_T1_(System.Collections.Generic.IEnumerable_T1_,System.Action_T1,PromptPlusLibrary.ITreeSelectControl_T__) 'PromptPlusLibrary\.ITreeSelectControl\\.Interaction\\(System\.Collections\.Generic\.IEnumerable\, System\.Action\\>\)')\.
The tasks are awaited sequentially \(blocking\) so tree construction remains deterministic\.
```csharp
PromptPlusLibrary.ITreeSelectControl InteractionAsync(System.Collections.Generic.IEnumerable items, System.Func,System.Threading.Tasks.Task> interactionAction);
```
#### Type parameters
`T1`
#### Parameters
`items` [System\.Collections\.Generic\.IEnumerable<](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.ienumerable-1 'System\.Collections\.Generic\.IEnumerable\`1')[T1](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.InteractionAsync_T1_(System.Collections.Generic.IEnumerable_T1_,System.Func_T1,PromptPlusLibrary.ITreeSelectControl_T_,System.Threading.Tasks.Task_).T1 'PromptPlusLibrary\.ITreeSelectControl\\.InteractionAsync\\(System\.Collections\.Generic\.IEnumerable\, System\.Func\,System\.Threading\.Tasks\.Task\>\)\.T1')[>](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.ienumerable-1 'System\.Collections\.Generic\.IEnumerable\`1')
`interactionAction` [System\.Func<](https://learn.microsoft.com/en-us/dotnet/api/system.func-3 'System\.Func\`3')[T1](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.InteractionAsync_T1_(System.Collections.Generic.IEnumerable_T1_,System.Func_T1,PromptPlusLibrary.ITreeSelectControl_T_,System.Threading.Tasks.Task_).T1 'PromptPlusLibrary\.ITreeSelectControl\\.InteractionAsync\\(System\.Collections\.Generic\.IEnumerable\, System\.Func\,System\.Threading\.Tasks\.Task\>\)\.T1')[,](https://learn.microsoft.com/en-us/dotnet/api/system.func-3 'System\.Func\`3')[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[,](https://learn.microsoft.com/en-us/dotnet/api/system.func-3 'System\.Func\`3')[System\.Threading\.Tasks\.Task](https://learn.microsoft.com/en-us/dotnet/api/system.threading.tasks.task 'System\.Threading\.Tasks\.Task')[>](https://learn.microsoft.com/en-us/dotnet/api/system.func-3 'System\.Func\`3')
#### Returns
[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
When [items](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.InteractionAsync_T1_(System.Collections.Generic.IEnumerable_T1_,System.Func_T1,PromptPlusLibrary.ITreeSelectControl_T_,System.Threading.Tasks.Task_).items 'PromptPlusLibrary\.ITreeSelectControl\\.InteractionAsync\\(System\.Collections\.Generic\.IEnumerable\, System\.Func\,System\.Threading\.Tasks\.Task\>\)\.items') or [interactionAction](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.InteractionAsync_T1_(System.Collections.Generic.IEnumerable_T1_,System.Func_T1,PromptPlusLibrary.ITreeSelectControl_T_,System.Threading.Tasks.Task_).interactionAction 'PromptPlusLibrary\.ITreeSelectControl\\.InteractionAsync\\(System\.Collections\.Generic\.IEnumerable\, System\.Func\,System\.Threading\.Tasks\.Task\>\)\.interactionAction') is `null`\.
## ITreeSelectControl\\.Options\(Action\\) Method
Applies the shared control options \(prompt, tooltips, abort behavior\)\.
```csharp
PromptPlusLibrary.ITreeSelectControl Options(System.Action options);
```
#### Parameters
`options` [System\.Action<](https://learn.microsoft.com/en-us/dotnet/api/system.action-1 'System\.Action\`1')[IControlOptions](IControlOptions.md 'PromptPlusLibrary\.IControlOptions')[>](https://learn.microsoft.com/en-us/dotnet/api/system.action-1 'System\.Action\`1')
#### Returns
[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
When [options](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.Options(System.Action_PromptPlusLibrary.IControlOptions_).options 'PromptPlusLibrary\.ITreeSelectControl\\.Options\(System\.Action\\)\.options') is `null`\.
## ITreeSelectControl\\.PageSize\(byte\) Method
Sets the maximum number of visible rows per page \(0 = auto\-fit\)\.
```csharp
PromptPlusLibrary.ITreeSelectControl PageSize(byte value);
```
#### Parameters
`value` [System\.Byte](https://learn.microsoft.com/en-us/dotnet/api/system.byte 'System\.Byte')
#### Returns
[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')
## ITreeSelectControl\\.PathSeparator\(char\) Method
Sets the character used to compose the full path in the answer line\. Default is `'/'`\.
```csharp
PromptPlusLibrary.ITreeSelectControl PathSeparator(char value);
```
#### Parameters
`value` [System\.Char](https://learn.microsoft.com/en-us/dotnet/api/system.char 'System\.Char')
#### Returns
[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')
## ITreeSelectControl\\.PredicateSelected\(Func\\) Method
Sets a validation predicate evaluated when the user presses Enter\. When it returns
`false`, the selection is rejected and a generic error is shown\.
```csharp
PromptPlusLibrary.ITreeSelectControl PredicateSelected(System.Func validselect);
```
#### Parameters
`validselect` [System\.Func<](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[,](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')[>](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')
#### Returns
[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')
## ITreeSelectControl\\.PredicateSelectedAsync\(Func\\>\) Method
Sets an asynchronous validation predicate evaluated \(blocking\) when the user presses Enter\.
```csharp
PromptPlusLibrary.ITreeSelectControl PredicateSelectedAsync(System.Func> validselect);
```
#### Parameters
`validselect` [System\.Func<](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[,](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[System\.Threading\.Tasks\.Task<](https://learn.microsoft.com/en-us/dotnet/api/system.threading.tasks.task-1 'System\.Threading\.Tasks\.Task\`1')[System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')[>](https://learn.microsoft.com/en-us/dotnet/api/system.threading.tasks.task-1 'System\.Threading\.Tasks\.Task\`1')[>](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')
#### Returns
[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')
### Remarks
The asynchronous predicate is evaluated synchronously \(blocking\) on the UI thread\.
## ITreeSelectControl\\.Root\(T, bool\) Method
Sets the root value shown as the top\-level node\. Required\.
```csharp
PromptPlusLibrary.ITreeSelectControl Root(T value, bool disable=false);
```
#### Parameters
`value` [T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')
The root value\. Cannot be `null`\.
`disable` [System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')
When `true`, the root cannot be confirmed\. Default is `false`\.
#### Returns
[PromptPlusLibrary\.ITreeSelectControl<](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\\.T')[>](ITreeSelectControl_T_.md 'PromptPlusLibrary\.ITreeSelectControl\')
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
When [value](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.Root(T,bool).value 'PromptPlusLibrary\.ITreeSelectControl\\.Root\(T, bool\)\.value') is `null`\.
## ITreeSelectControl\\.Run\(CancellationToken\) Method
Displays the TreeSelect control and blocks until the user confirms or cancels\.
```csharp
PromptPlusLibrary.ResultPrompt Run(System.Threading.CancellationToken token=default(System.Threading.CancellationToken));
```
#### Parameters
`token` [System\.Threading\.CancellationToken](https://learn.microsoft.com/en-us/dotnet/api/system.threading.cancellationtoken 'System\.Threading\.CancellationToken')
#### Returns
[PromptPlusLibrary\.ResultPrompt<](ResultPrompt_T_.md 'PromptPlusLibrary\.ResultPrompt\')[T](ITreeSelectControl_T_.md#PromptPlusLibrary.ITreeSelectControl_T_.T 'PromptPlusLibrary\.ITreeSelectControl\