Quickstart: Existing App

Use this path when you already have a .NET console app and want to add Tessera.

Goal

Integrate Tessera with minimal disruption, confirm runtime behavior, and then expand safely.

1. From your existing project folder

bash.sh

dotnet add package Tessera

2. Update Program.cs

Start from this minimal integration template:

csharp.cs

using Tessera;
using Tessera.Controls;
using Tessera.Layout;

var app = TesseraApplication.CreateBuilder()
    .UseApp<OrdersApp>()
    .Build();

await app.RunAsync();

internal sealed class OrdersApp : TesseraApp
{
    private readonly Button _refresh = new() { Text = "Refresh" };
    private int _count = 12;

    public OrdersApp()
    {
        _refresh.Activated += (_, _) => _count++;
    }

    public override TesseraEffect? Update(Message message)
    {
        return message is KeyPressed key && key.IsCharacter('q', ModifierKeys.Ctrl)
            ? TesseraEffects.Quit
            : null;
    }

    public override Screen Build(ScreenContext context)
    {
        return Screen.Build(window =>
        {
            window.Padding(1);
            window.Footer(1, new StatusBar
            {
                LeftText = $"Orders: {_count}",
                RightText = "Enter refreshes   Ctrl+Q quits"
            });
            window.Body(body => body.Center(_refresh, width: 18, height: 3));
        });
    }
}

3. Run and validate

bash.sh

dotnet run

Verify:

• the UI opens in the terminal
• interaction works (Enter, navigation keys, Ctrl+Q)
• app exits cleanly and restores terminal state

4. Common migration mistakes

• keeping old console loop code active alongside Tessera startup
• mixing business mutation directly inside rendering code
• starting with Tessera.Core namespaces before the primary app model is in place

Keep normal app integration inside:

• Tessera
• Tessera.Controls
• Tessera.Layout
• Tessera.Styles (when theming starts)

What to do next

1. Read Your First App for lifecycle details.
2. Use App Model for message/effect patterns.
3. Use Widget Pages to pick controls quickly.