PromptPlus

# PromptPlus ## **Secret — Methods** [](https://www.nuget.org/packages/PromptPlus) [](https://opensource.org/licenses/MIT) [](https://dotnet.microsoft.com/)

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Every fluent method on IInputSecretControl. Each returns the same control instance, so calls chain in any order. Call Run last.

The factory is PromptPlus.Controls.Secret(string prompt = "", string? description = null), which returns IInputSecretControl.

Quick jump: MaskSecret · InputToCase · AcceptInput · MaxLength · PredicateValid · PredicateValidAsync · ChangeDescription · ChangeDescriptionAsync · Styles · Options · Run

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Masking & reveal

MaskSecret

IInputSecretControl MaskSecret(char? value = null, bool enabledView = true)

Sets the character that hides each typed character on screen, and whether the user may reveal the plain text with F2.

Parameter	Meaning
value	The mask symbol shown in place of each character. When null, falls back to PromptPlus.Config.SecretChar (default '#').
enabledView	When true (default), the user can press F2 to toggle between the masked view and the plain text. When false, the value can never be revealed on screen.

using PromptPlusLibrary;

// Hide with '*', and forbid reveal
PromptPlus.Controls.Secret("PIN")
    .MaskSecret('*', enabledView: false)
    .Run();

If you never call MaskSecret, the control still masks input using PromptPlus.Config.SecretChar and allows F2 reveal (enabledView defaults to on). Call it only to change the symbol or to disable reveal. See Operations → The mask character.

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Restricting what can be typed

InputToCase

IInputSecretControl InputToCase(CaseOptions value)

Coerces every typed character to a casing rule as it is entered.

CaseOptions	Effect
Any	No transformation (default)
Uppercase	Letters become upper case
Lowercase	Letters become lower case

using PromptPlusLibrary;
using ConsolePlusLibrary;   // CaseOptions

PromptPlus.Controls.Secret("ApiKey", "Input is transformed to lowercase")
    .InputToCase(CaseOptions.Lowercase)
    .Run();

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AcceptInput

IInputSecretControl AcceptInput(Func<char, bool> value)

A per-keystroke filter. The callback receives each character the moment it is typed; return true to accept it or false to silently ignore it. Rejected characters never enter the field.

using PromptPlusLibrary;

// Digits only
PromptPlus.Controls.Secret("PIN")
    .AcceptInput(char.IsDigit)
    .Run();

Throws ArgumentNullException if value is null.

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MaxLength

IInputSecretControl MaxLength(int maxLength)

Caps the number of characters. Once the limit is reached, further keystrokes are ignored. A value of 0 or less means no limit (the default).

using PromptPlusLibrary;

PromptPlus.Controls.Secret("PIN", "Max 4 digits")
    .MaxLength(4)
    .Run();

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Validating the confirmed value

Validation runs when the user presses Enter. If it fails, the control stays open and shows an error (styled with InputStyles.Error); the value is only returned when validation passes.

PredicateValid

Two overloads — pick the tuple form when you want to show a custom message.

IInputSecretControl PredicateValid(Func<string, bool> value)
IInputSecretControl PredicateValid(Func<string, (bool, string?)> value)

Overload	Return	Behavior
Func<string, bool>	true = valid	On failure, a generic error is shown
Func<string, (bool, string?)>	(isValid, message)	On failure, message is shown (or a generic one if null)

using PromptPlusLibrary;
using System.Text.RegularExpressions;

// Boolean form — complexity rule
PromptPlus.Controls.Secret("Password", "Min 8 chars with upper/lower/digit/special")
    .PredicateValid(x =>
    {
        var rule = new Regex("^(?=.*?[A-Z])(?=.*?[a-z])(?=.*?[0-9])(?=.*?[#?!@$%^&*-]).{8,}$");
        return rule.IsMatch(x);
    })
    .Run();

// Message form
PromptPlus.Controls.Secret("PIN")
    .PredicateValid(v => v.Length == 4
        ? (true, null)
        : (false, "PIN must be exactly 4 digits"))
    .Run();

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PredicateValidAsync

Asynchronous counterparts of PredicateValid, for validation that awaits I/O (a credential store, an HTTP call).

IInputSecretControl PredicateValidAsync(Func<string, Task<bool>> value)
IInputSecretControl PredicateValidAsync(Func<string, Task<(bool, string?)>> value)

using PromptPlusLibrary;

PromptPlus.Controls.Secret("Password", "Minimum 8 chars (async)")
    .PredicateValidAsync(async x =>
    {
        await Task.Delay(1);
        return x.Length < 8
            ? (false, "Password must have at least 8 chars")
            : (true, (string?)null);
    })
    .Run();

⚠️ The async predicate is awaited synchronously (blocking) on the UI thread — it does not run in parallel with the render loop. Keep it fast; long calls freeze the prompt until they return.

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Dynamic description

ChangeDescription

IInputSecretControl ChangeDescription(Func<string, string> value)

Recomputes the description line on every keystroke. The callback receives the current text and returns the description to display — handy for a live length counter.

using PromptPlusLibrary;

PromptPlus.Controls.Secret("Password", "Minimum 8 chars")
    .ChangeDescription(input => $"Length: {input.Length}")
    .Run();

Throws ArgumentNullException if value is null.

⚠️ The callback receives the raw text — show a derived value like input.Length, never the secret itself.

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ChangeDescriptionAsync

IInputSecretControl ChangeDescriptionAsync(Func<string, Task<string>> value)

Asynchronous version of ChangeDescription.

using PromptPlusLibrary;

PromptPlus.Controls.Secret("Password", "Minimum 8 chars (async)")
    .ChangeDescriptionAsync(async input =>
    {
        await Task.Delay(1);
        return $"Length: {input.Length}";
    })
    .Run();

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Appearance & behavior

Styles

IInputSecretControl Styles(InputStyles styleType, Style style)

Overrides the color of one visual region of this control instance. See the full region list and examples on the Styles page.

using PromptPlusLibrary;
using ConsolePlusLibrary;   // Color, Style live here

PromptPlus.Controls.Secret("PIN")
    .Styles(InputStyles.Answer, Color.Green)
    .Run();

Throws ArgumentNullException if style is null.

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Options

IInputSecretControl Options(Action<IControlOptions> options)

Overrides global behaviors (PromptPlus.Config) for this one control — prompt/description text, abort key, tooltip, hide-after-finish, and the extra-info affixes.

using PromptPlusLibrary;

PromptPlus.Controls.Secret("Password")
    .Options(o => o
        .EnabledAbortKey(false)   // no Esc for this field
        .ShowTooltip(true)
        .HideAfterFinish(true))   // erase the UI once confirmed
    .Run();

See Global Behaviors → Per-Control Override for the complete IControlOptions list.

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Running the control

Run

ResultPrompt<string> Run(CancellationToken token = default)

Renders the masked field and blocks until the user confirms (Enter) or aborts (Esc). Returns a ResultPrompt<string>.

Parameter	Meaning
token	A CancellationToken that cancels the prompt while it waits for input.

using PromptPlusLibrary;

using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(30));
var result = PromptPlus.Controls.Secret("Password").Run(cts.Token);

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See also

• Operations — how these methods behave at runtime
• Styles — the InputStyles regions
• Index — overview and method map
• Input → Methods — the full un-masked API for comparison

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