#### [PromptPlus](PromptPlus.md 'PromptPlus')
### [PromptPlusLibrary](PromptPlusLibrary.md 'PromptPlusLibrary')
## IMultiSelectControl\ Interface
Provides a fluent API for configuring and running a multi\-selection list control\.
```csharp
public interface IMultiSelectControl
```
#### Type parameters
`T`
The type of items shown in the list\.
### Remarks
The control renders a scrollable, optionally grouped list where the user navigates items
with the arrow keys, toggles individual checks with `Space`, and confirms the entire
selection with `Enter`\. Features include inline filtering \([Filter\(FilterMode\)](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.Filter(PromptPlusLibrary.FilterMode) 'PromptPlusLibrary\.IMultiSelectControl\\.Filter\(PromptPlusLibrary\.FilterMode\)')\),
optional grouped layout with header separators, history persistence \([EnableHistory\(string, Action<IHistoryOptions>\)](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.EnableHistory(string,System.Action_PromptPlusLibrary.IHistoryOptions_) 'PromptPlusLibrary\.IMultiSelectControl\\.EnableHistory\(string, System\.Action\\)')\),
range constraints \([Range\(int, Nullable<int>\)](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.Range(int,System.Nullable_int_) 'PromptPlusLibrary\.IMultiSelectControl\\.Range\(int, System\.Nullable\\)')\), and view\-only mode \([ViewOnly\(bool\)](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.ViewOnly(bool) 'PromptPlusLibrary\.IMultiSelectControl\\.ViewOnly\(bool\)')\)\.
Every configuration method returns the same [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance
so calls can be chained \(fluent style\)\. Call [Run\(CancellationToken\)](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.Run(System.Threading.CancellationToken) 'PromptPlusLibrary\.IMultiSelectControl\\.Run\(System\.Threading\.CancellationToken\)') last\.
### Methods
## IMultiSelectControl\\.AddGroupedItem\(string, T, bool, bool\) Method
Adds an item to a specific group in the list\.
```csharp
PromptPlusLibrary.IMultiSelectControl AddGroupedItem(string group, T value, bool ischecked=false, bool disable=false);
```
#### Parameters
`group` [System\.String](https://learn.microsoft.com/en-us/dotnet/api/system.string 'System\.String')
The name of the group\. Cannot be `null`\.
`value` [T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')
The item to add\. Cannot be `null`\.
`ischecked` [System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')
If `true`, the item is initially checked; otherwise, it is unchecked\.
`disable` [System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')
If `true`, the item is disabled and cannot be selected\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
Thrown if [group](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.AddGroupedItem(string,T,bool,bool).group 'PromptPlusLibrary\.IMultiSelectControl\\.AddGroupedItem\(string, T, bool, bool\)\.group') is `null`\.
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
Thrown if [value](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.AddGroupedItem(string,T,bool,bool).value 'PromptPlusLibrary\.IMultiSelectControl\\.AddGroupedItem\(string, T, bool, bool\)\.value') is `null`\.
## IMultiSelectControl\\.AddGroupedItems\(string, IEnumerable\, bool, bool\) Method
Adds a collection of items to a specific group in the list\.
```csharp
PromptPlusLibrary.IMultiSelectControl AddGroupedItems(string group, System.Collections.Generic.IEnumerable values, bool ischecked=false, bool disable=false);
```
#### Parameters
`group` [System\.String](https://learn.microsoft.com/en-us/dotnet/api/system.string 'System\.String')
The name of the group\. Cannot be `null`\.
`values` [System\.Collections\.Generic\.IEnumerable<](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.ienumerable-1 'System\.Collections\.Generic\.IEnumerable\`1')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.ienumerable-1 'System\.Collections\.Generic\.IEnumerable\`1')
The collection of items to add\. Cannot be `null`\.
`ischecked` [System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')
If `true`, the items are initially checked; otherwise, they are unchecked\.
`disable` [System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')
If `true`, all items are disabled and cannot be selected\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
Thrown if [group](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.AddGroupedItems(string,System.Collections.Generic.IEnumerable_T_,bool,bool).group 'PromptPlusLibrary\.IMultiSelectControl\\.AddGroupedItems\(string, System\.Collections\.Generic\.IEnumerable\, bool, bool\)\.group') is `null`\.
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
Thrown if [values](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.AddGroupedItems(string,System.Collections.Generic.IEnumerable_T_,bool,bool).values 'PromptPlusLibrary\.IMultiSelectControl\\.AddGroupedItems\(string, System\.Collections\.Generic\.IEnumerable\, bool, bool\)\.values') is `null`\.
## IMultiSelectControl\\.AddItem\(T, bool, bool\) Method
Adds an item to the list\.
```csharp
PromptPlusLibrary.IMultiSelectControl AddItem(T value, bool ischecked=false, bool disable=false);
```
#### Parameters
`value` [T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')
The item to add\. Cannot be `null`\.
`ischecked` [System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')
If `true`, the item is initially checked; otherwise, it is unchecked\.
`disable` [System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')
If `true`, the item is disabled and cannot be selected\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
Thrown if [value](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.AddItem(T,bool,bool).value 'PromptPlusLibrary\.IMultiSelectControl\\.AddItem\(T, bool, bool\)\.value') is `null`\.
## IMultiSelectControl\\.AddItems\(IEnumerable\, bool, bool\) Method
Adds a collection of items to the list\.
```csharp
PromptPlusLibrary.IMultiSelectControl AddItems(System.Collections.Generic.IEnumerable values, bool ischecked=false, bool disable=false);
```
#### Parameters
`values` [System\.Collections\.Generic\.IEnumerable<](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.ienumerable-1 'System\.Collections\.Generic\.IEnumerable\`1')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.ienumerable-1 'System\.Collections\.Generic\.IEnumerable\`1')
The collection of items to add\. Cannot be `null`\.
`ischecked` [System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')
If `true`, the item is initially checked; otherwise, it is unchecked\.
`disable` [System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')
If `true`, all items are disabled and cannot be selected\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
Thrown if [values](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.AddItems(System.Collections.Generic.IEnumerable_T_,bool,bool).values 'PromptPlusLibrary\.IMultiSelectControl\\.AddItems\(System\.Collections\.Generic\.IEnumerable\, bool, bool\)\.values') is `null`\.
## IMultiSelectControl\\.AddSeparator\(SeparatorLine, Nullable\\) Method
Adds a visual separator line to the list\.
```csharp
PromptPlusLibrary.IMultiSelectControl AddSeparator(PromptPlusLibrary.SeparatorLine separatorLine=PromptPlusLibrary.SeparatorLine.SingleLine, System.Nullable value=null);
```
#### Parameters
`separatorLine` [SeparatorLine](SeparatorLine.md 'PromptPlusLibrary\.SeparatorLine')
The type of separator line\. Default is [SingleLine](SeparatorLine.md#PromptPlusLibrary.SeparatorLine.SingleLine 'PromptPlusLibrary\.SeparatorLine\.SingleLine')\.
`value` [System\.Nullable<](https://learn.microsoft.com/en-us/dotnet/api/system.nullable-1 'System\.Nullable\`1')[System\.Char](https://learn.microsoft.com/en-us/dotnet/api/system.char 'System\.Char')[>](https://learn.microsoft.com/en-us/dotnet/api/system.nullable-1 'System\.Nullable\`1')
The character to use for the separator line\. Only used when [separatorLine](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.AddSeparator(PromptPlusLibrary.SeparatorLine,System.Nullable_char_).separatorLine 'PromptPlusLibrary\.IMultiSelectControl\\.AddSeparator\(PromptPlusLibrary\.SeparatorLine, System\.Nullable\\)\.separatorLine') is [UserChar](SeparatorLine.md#PromptPlusLibrary.SeparatorLine.UserChar 'PromptPlusLibrary\.SeparatorLine\.UserChar')\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
## IMultiSelectControl\\.ChangeDescription\(Func\\) Method
Dynamically updates the control description based on the currently selected item\.
```csharp
PromptPlusLibrary.IMultiSelectControl ChangeDescription(System.Func value);
```
#### Parameters
`value` [System\.Func<](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.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\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
Thrown if [value](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.ChangeDescription(System.Func_T,string_).value 'PromptPlusLibrary\.IMultiSelectControl\\.ChangeDescription\(System\.Func\\)\.value') is `null`\.
## IMultiSelectControl\\.ChangeDescriptionAsync\(Func\\>\) Method
Dynamically updates the control description based on the currently selected item using an asynchronous callback\.
```csharp
PromptPlusLibrary.IMultiSelectControl ChangeDescriptionAsync(System.Func> value);
```
#### Parameters
`value` [System\.Func<](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.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')
A function that asynchronously receives the current item and returns the description\. Cannot be `null`\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
Thrown if [value](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.ChangeDescriptionAsync(System.Func_T,System.Threading.Tasks.Task_string__).value 'PromptPlusLibrary\.IMultiSelectControl\\.ChangeDescriptionAsync\(System\.Func\\>\)\.value') is `null`\.
## IMultiSelectControl\\.Default\(IEnumerable\, bool\) Method
Sets the initial selected item and checked items for the MultiSelect control\.
The selected item is the first item in the collection that matches any provided value, and checked items are those that match the provided values\.
```csharp
PromptPlusLibrary.IMultiSelectControl Default(System.Collections.Generic.IEnumerable values, bool useDefaultHistory=true);
```
#### Parameters
`values` [System\.Collections\.Generic\.IEnumerable<](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.ienumerable-1 'System\.Collections\.Generic\.IEnumerable\`1')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.ienumerable-1 'System\.Collections\.Generic\.IEnumerable\`1')
The initial values\. Cannot be `null`\.
`useDefaultHistory` [System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')
If `true`, uses values from history \(selected item and checked items\) when history is enabled; otherwise, uses [values](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.Default(System.Collections.Generic.IEnumerable_T_,bool).values 'PromptPlusLibrary\.IMultiSelectControl\\.Default\(System\.Collections\.Generic\.IEnumerable\, bool\)\.values')\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
Thrown if [values](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.Default(System.Collections.Generic.IEnumerable_T_,bool).values 'PromptPlusLibrary\.IMultiSelectControl\\.Default\(System\.Collections\.Generic\.IEnumerable\, bool\)\.values') is `null`\.
## IMultiSelectControl\\.DefaultMatchBy\(Func\\) Method
Sets a custom item comparator for determining item equality\.
```csharp
PromptPlusLibrary.IMultiSelectControl DefaultMatchBy(System.Func comparer);
```
#### Parameters
`comparer` [System\.Func<](https://learn.microsoft.com/en-us/dotnet/api/system.func-3 'System\.Func\`3')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[,](https://learn.microsoft.com/en-us/dotnet/api/system.func-3 'System\.Func\`3')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.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')
A function that compares two items and returns `true` if they are equal\. Cannot be `null`\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
Thrown if [comparer](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.DefaultMatchBy(System.Func_T,T,bool_).comparer 'PromptPlusLibrary\.IMultiSelectControl\\.DefaultMatchBy\(System\.Func\\)\.comparer') is `null`\.
## IMultiSelectControl\\.EnableHistory\(string, Action\\) Method
Enables history and applies custom options to the history feature\.
```csharp
PromptPlusLibrary.IMultiSelectControl EnableHistory(string filename, System.Action? options=null);
```
#### Parameters
`filename` [System\.String](https://learn.microsoft.com/en-us/dotnet/api/system.string 'System\.String')
The name of the file to store history\. Cannot be `null`\.
`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')
An action to configure [IHistoryOptions](IHistoryOptions.md 'PromptPlusLibrary\.IHistoryOptions')\. Optional\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
Thrown if [filename](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.EnableHistory(string,System.Action_PromptPlusLibrary.IHistoryOptions_).filename 'PromptPlusLibrary\.IMultiSelectControl\\.EnableHistory\(string, System\.Action\\)\.filename') is `null`\.
## IMultiSelectControl\\.ExtraInfo\(Func\\) Method
Registers a callback that returns an additional informational line rendered below the
highlighted item\. Useful for displaying metadata without cluttering the list\.
```csharp
PromptPlusLibrary.IMultiSelectControl ExtraInfo(System.Func extraInfoNode);
```
#### Parameters
`extraInfoNode` [System\.Func<](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.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 focused item and returns the extra text, or `null` to show nothing\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
## IMultiSelectControl\\.ExtraInfoAsync\(Func\\>\) Method
Asynchronous counterpart of [ExtraInfo\(Func<T,string>\)](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.ExtraInfo(System.Func_T,string_) 'PromptPlusLibrary\.IMultiSelectControl\\.ExtraInfo\(System\.Func\\)')\. The task is awaited
synchronously \(blocking\) on the UI thread each time the cursor moves\.
```csharp
PromptPlusLibrary.IMultiSelectControl ExtraInfoAsync(System.Func> extraInfoNode);
```
#### Parameters
`extraInfoNode` [System\.Func<](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.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')
An async function that receives the focused item and returns the extra text\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
## IMultiSelectControl\\.Filter\(FilterMode\) Method
Sets the filter strategy for filtering items in the collection\. Default is [Disabled](FilterMode.md#PromptPlusLibrary.FilterMode.Disabled 'PromptPlusLibrary\.FilterMode\.Disabled')\.
```csharp
PromptPlusLibrary.IMultiSelectControl Filter(PromptPlusLibrary.FilterMode value);
```
#### Parameters
`value` [FilterMode](FilterMode.md 'PromptPlusLibrary\.FilterMode')
The [FilterMode](FilterMode.md 'PromptPlusLibrary\.FilterMode') to apply\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
## IMultiSelectControl\\.HideTipGroup\(bool\) Method
Hides the group name tip\. Default is `false`\.
```csharp
PromptPlusLibrary.IMultiSelectControl HideTipGroup(bool value=true);
```
#### Parameters
`value` [System\.Boolean](https://learn.microsoft.com/en-us/dotnet/api/system.boolean 'System\.Boolean')
If `true`, hides the group name tip; otherwise, shows it\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
## IMultiSelectControl\\.Interaction\\(IEnumerable\, Action\\>\) Method
Iterates [items](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.Interaction_T1_(System.Collections.Generic.IEnumerable_T1_,System.Action_T1,PromptPlusLibrary.IMultiSelectControl_T__).items 'PromptPlusLibrary\.IMultiSelectControl\\.Interaction\\(System\.Collections\.Generic\.IEnumerable\, System\.Action\\>\)\.items') and invokes [interactionAction](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.Interaction_T1_(System.Collections.Generic.IEnumerable_T1_,System.Action_T1,PromptPlusLibrary.IMultiSelectControl_T__).interactionAction 'PromptPlusLibrary\.IMultiSelectControl\\.Interaction\\(System\.Collections\.Generic\.IEnumerable\, System\.Action\\>\)\.interactionAction') for each element,
giving the caller a chance to call [AddItem\(T, bool, bool\)](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.AddItem(T,bool,bool) 'PromptPlusLibrary\.IMultiSelectControl\\.AddItem\(T, bool, bool\)') or [AddGroupedItem\(string, T, bool, bool\)](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.AddGroupedItem(string,T,bool,bool) 'PromptPlusLibrary\.IMultiSelectControl\\.AddGroupedItem\(string, T, bool, bool\)') programmatically\.
```csharp
PromptPlusLibrary.IMultiSelectControl Interaction(System.Collections.Generic.IEnumerable items, System.Action> interactionAction);
```
#### Type parameters
`T1`
The type of elements in the input sequence\.
#### 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](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.Interaction_T1_(System.Collections.Generic.IEnumerable_T1_,System.Action_T1,PromptPlusLibrary.IMultiSelectControl_T__).T1 'PromptPlusLibrary\.IMultiSelectControl\\.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')
The input sequence to iterate\. Cannot be `null`\.
`interactionAction` [System\.Action<](https://learn.microsoft.com/en-us/dotnet/api/system.action-2 'System\.Action\`2')[T1](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.Interaction_T1_(System.Collections.Generic.IEnumerable_T1_,System.Action_T1,PromptPlusLibrary.IMultiSelectControl_T__).T1 'PromptPlusLibrary\.IMultiSelectControl\\.Interaction\\(System\.Collections\.Generic\.IEnumerable\, System\.Action\\>\)\.T1')[,](https://learn.microsoft.com/en-us/dotnet/api/system.action-2 'System\.Action\`2')[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[>](https://learn.microsoft.com/en-us/dotnet/api/system.action-2 'System\.Action\`2')
The action invoked for each element\. Cannot be `null`\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
Thrown if [interactionAction](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.Interaction_T1_(System.Collections.Generic.IEnumerable_T1_,System.Action_T1,PromptPlusLibrary.IMultiSelectControl_T__).interactionAction 'PromptPlusLibrary\.IMultiSelectControl\\.Interaction\\(System\.Collections\.Generic\.IEnumerable\, System\.Action\\>\)\.interactionAction') is `null`\.
## IMultiSelectControl\\.InteractionAsync\\(IEnumerable\, Func\,Task\>\) Method
Asynchronous counterpart of [Interaction<T1>\(IEnumerable<T1>, Action<T1,IMultiSelectControl<T>>\)](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.Interaction_T1_(System.Collections.Generic.IEnumerable_T1_,System.Action_T1,PromptPlusLibrary.IMultiSelectControl_T__) 'PromptPlusLibrary\.IMultiSelectControl\\.Interaction\\(System\.Collections\.Generic\.IEnumerable\, System\.Action\\>\)')\. The task returned by
[interactionAction](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.InteractionAsync_T1_(System.Collections.Generic.IEnumerable_T1_,System.Func_T1,PromptPlusLibrary.IMultiSelectControl_T_,System.Threading.Tasks.Task_).interactionAction 'PromptPlusLibrary\.IMultiSelectControl\\.InteractionAsync\\(System\.Collections\.Generic\.IEnumerable\, System\.Func\,System\.Threading\.Tasks\.Task\>\)\.interactionAction') is awaited synchronously \(blocking\)\.
```csharp
PromptPlusLibrary.IMultiSelectControl InteractionAsync(System.Collections.Generic.IEnumerable items, System.Func,System.Threading.Tasks.Task> interactionAction);
```
#### Type parameters
`T1`
The type of elements in the input sequence\.
#### 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](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.InteractionAsync_T1_(System.Collections.Generic.IEnumerable_T1_,System.Func_T1,PromptPlusLibrary.IMultiSelectControl_T_,System.Threading.Tasks.Task_).T1 'PromptPlusLibrary\.IMultiSelectControl\\.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')
The input sequence to iterate\. Cannot be `null`\.
`interactionAction` [System\.Func<](https://learn.microsoft.com/en-us/dotnet/api/system.func-3 'System\.Func\`3')[T1](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.InteractionAsync_T1_(System.Collections.Generic.IEnumerable_T1_,System.Func_T1,PromptPlusLibrary.IMultiSelectControl_T_,System.Threading.Tasks.Task_).T1 'PromptPlusLibrary\.IMultiSelectControl\\.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\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[,](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')
The asynchronous action invoked for each element\. Cannot be `null`\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
Thrown if [interactionAction](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.InteractionAsync_T1_(System.Collections.Generic.IEnumerable_T1_,System.Func_T1,PromptPlusLibrary.IMultiSelectControl_T_,System.Threading.Tasks.Task_).interactionAction 'PromptPlusLibrary\.IMultiSelectControl\\.InteractionAsync\\(System\.Collections\.Generic\.IEnumerable\, System\.Func\,System\.Threading\.Tasks\.Task\>\)\.interactionAction') is `null`\.
## IMultiSelectControl\\.Options\(Action\\) Method
Applies custom options to the control\.
```csharp
PromptPlusLibrary.IMultiSelectControl 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')
An action to configure [IControlOptions](IControlOptions.md 'PromptPlusLibrary\.IControlOptions')\. Cannot be `null`\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
#### Exceptions
[System\.ArgumentNullException](https://learn.microsoft.com/en-us/dotnet/api/system.argumentnullexception 'System\.ArgumentNullException')
Thrown if [options](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.Options(System.Action_PromptPlusLibrary.IControlOptions_).options 'PromptPlusLibrary\.IMultiSelectControl\\.Options\(System\.Action\\)\.options') is `null`\.
## IMultiSelectControl\\.PageSize\(byte\) Method
Sets the maximum number of items to display per page\. Default value is 0\.
Valid range is 0\-255\.
```csharp
PromptPlusLibrary.IMultiSelectControl PageSize(byte value);
```
#### Parameters
`value` [System\.Byte](https://learn.microsoft.com/en-us/dotnet/api/system.byte 'System\.Byte')
The maximum number of items per page\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
### Remarks
A value of 0 automatically calculates the page size based on screen height, reserving lines for header, footer, and pagination\.
If the provided value is greater than the available screen height \(minus reserved lines\), it is coerced to the maximum allowed value\.
## IMultiSelectControl\\.PredicateChecked\(Func\\) Method
Sets a synchronous validation predicate executed when the user attempts to check an item\.
Returns `false` to reject the check and show a generic error\. Never evaluated when
unchecking an item — unchecking is always allowed for non\-disabled items\.
```csharp
PromptPlusLibrary.IMultiSelectControl PredicateChecked(System.Func validselect);
```
#### Parameters
`validselect` [System\.Func<](https://learn.microsoft.com/en-us/dotnet/api/system.func-2 'System\.Func\`2')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.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')
A predicate that returns `true` when the item can be checked\.
#### Returns
[PromptPlusLibrary\.IMultiSelectControl<](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')[T](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.T 'PromptPlusLibrary\.IMultiSelectControl\\.T')[>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\')
The current [IMultiSelectControl<T>](IMultiSelectControl_T_.md 'PromptPlusLibrary\.IMultiSelectControl\') instance for chaining\.
## IMultiSelectControl\\.PredicateCheckedAsync\(Func\\>\) Method
Asynchronous counterpart of [PredicateChecked\(Func<T,bool>\)](IMultiSelectControl_T_.md#PromptPlusLibrary.IMultiSelectControl_T_.PredicateChecked(System.Func_T,bool_) 'PromptPlusLibrary\.IMultiSelectControl\\.PredicateChecked\(System\.Func\\)')\.
```csharp
PromptPlusLibrary.IMultiSelectControl PredicateCheckedAsync(System.Func> validselect);
```
#### Parameters