Shell | Dialogs

All user-facing dialogs in Shiny Shell go through the IDialogs interface. Inject it into your ViewModels via constructor injection.

public class MyViewModel(IDialogs dialogs)
{
    // dialogs is ready to use
}

IDialogs is registered as a singleton by UseShinyShell() and dispatches all calls to the UI thread automatically — safe to call from any thread.

Tip

Use IDialogs instead of Shell.Current.DisplayAlert, Shell.Current.DisplayPromptAsync, or Shell.Current.DisplayActionSheet — it’s injectable, mockable, and testable.

Custom Dialog Providers

The default IDialogs implementation (ShellDialogs) uses MAUI’s built-in Shell dialogs. You can replace it with your own implementation — for example to plug in a third-party dialog library, a custom bottom-sheet, or a test double — using UseDialogs<TDialog>():

builder
    .UseMauiApp<App>()
    .UseShinyShell(x => x
        .AddGeneratedMaps()
        .UseDialogs<MyCustomDialogs>()
    );

public class MyCustomDialogs : IDialogs
{
    public Task Alert(string? title, string message, string acceptText = "OK") { /* ... */ }
    public Task<bool> Confirm(string? title, string message, string acceptText = "Yes", string cancelText = "No") { /* ... */ }
    public Task<string?> Prompt(string? title, string message, string acceptText = "OK", string cancelText = "Cancel", string? placeholder = null, string initialValue = "", int maxLength = -1, Keyboard? keyboard = null) { /* ... */ }
    public Task<string> ActionSheet(string? title, string? cancel, string? destruction, params string[] buttons) { /* ... */ }
}

The default registration uses TryAddSingleton, so calling UseDialogs<>() always wins — regardless of call order.

Alert

Display an informational dialog with a single button.

await dialogs.Alert("Error", "Something went wrong");

// With custom button text
await dialogs.Alert("Success", "Item saved successfully", "Got it");

Parameter	Type	Default	Description
title	string?	—	Alert title. Pass null to omit.
message	string	—	Alert body text (required)
acceptText	string	"OK"	Button text

Confirm

Display a confirmation dialog and return the user’s choice.

bool confirmed = await dialogs.Confirm(
    "Delete Item",
    "Are you sure you want to delete this?",
    "Delete",
    "Cancel"
);

if (confirmed)
{
    // proceed with deletion
}

Parameter	Type	Default	Description
title	string?	—	Dialog title. Pass null to omit.
message	string	—	Dialog body text (required)
acceptText	string	"Yes"	Accept button text
cancelText	string	"No"	Cancel button text

Prompt

Display a text input dialog. Returns the entered text, or null if the user cancelled.

// Simple prompt
var name = await dialogs.Prompt("Name", "What is your name?");
if (name != null)
{
    // user entered a value
}

// With all options
var pin = await dialogs.Prompt(
    "Security",
    "Enter your PIN",
    acceptText: "Submit",
    cancelText: "Cancel",
    placeholder: "4-digit PIN",
    initialValue: "",
    maxLength: 4,
    keyboard: Keyboard.Numeric
);

Parameter	Type	Default	Description
title	string?	—	Dialog title. Pass null to omit.
message	string	—	Dialog body text (required)
acceptText	string	"OK"	Accept button text
cancelText	string	"Cancel"	Cancel button text
placeholder	string?	null	Placeholder text shown when the input is empty
initialValue	string	""	Pre-filled input value
maxLength	int	-1	Maximum characters allowed (-1 = no limit)
keyboard	Keyboard?	null	Keyboard type (Keyboard.Numeric, Keyboard.Email, etc.)

ActionSheet

Display an action sheet with multiple options. Returns the text of the selected button.

var action = await dialogs.ActionSheet(
    "Photo Options",
    "Cancel",
    "Delete Photo",
    "Take Photo", "Choose from Library", "Share"
);

switch (action)
{
    case "Take Photo":
        // open camera
        break;
    case "Choose from Library":
        // open gallery
        break;
    case "Share":
        // share photo
        break;
    case "Delete Photo":
        // destructive action
        break;
}

Parameter	Type	Description
title	string?	Sheet title. Pass null to omit.
cancel	string?	Cancel button text. Pass null to omit.
destruction	string?	Destructive action text (shown in red on some platforms). Pass null to omit.
buttons	string[]	Action button labels

Common Patterns

Navigation Confirmation

Use IDialogs with INavigationConfirmation to guard unsaved changes:

public class EditViewModel(INavigator navigator, IDialogs dialogs) :
    INavigationConfirmation
{
    public bool HasUnsavedChanges { get; set; }

    public async Task<bool> CanNavigate()
    {
        if (!HasUnsavedChanges)
            return true;

        return await dialogs.Confirm(
            "Unsaved Changes",
            "You have unsaved changes. Discard them?"
        );
    }
}

Delete Confirmation

public class ItemViewModel(INavigator navigator, IDialogs dialogs)
{
    async Task DeleteItem()
    {
        if (await dialogs.Confirm("Delete", "This action cannot be undone."))
        {
            await itemService.Delete(ItemId);
            await navigator.GoBack(("Deleted", true));
        }
    }
}

User Input

public class ListViewModel(IDialogs dialogs)
{
    async Task RenameItem(Item item)
    {
        var newName = await dialogs.Prompt(
            "Rename",
            "Enter a new name",
            placeholder: "New name",
            initialValue: item.Name,
            maxLength: 100
        );

        if (newName != null)
            item.Name = newName;
    }
}