docs: Improve Installing Extensions docs

doc/GettingStarted.md

@@ -104,10 +104,47 @@ var builder = this.CreateBuilder(args)
     );
 ```
 
+Add a `protected` property named Host of type `IHost` to your App.xaml.cs file:
+
+```csharp
+protected IHost? Host { get; private set; }
+```
+
+After creating the `builder`, initialize the `Host` by building it:
+
+```csharp
+Host = builder.Build();
+```
+
 ### Step 3: Use the Builder to Create the Main Window
 
 Finally, instead of directly creating an instance of a `Window` using `MainWindow = new Window()`, use the `builder` to set up the main window:
 
-```csharp
-MainWindow = builder.Window;
+```diff
+-MainWindow = new Window();
+
+var builder = this.CreateBuilder(args)
+    .Configure(host => host
+        // Configure the host builder
+    );
+
++MainWindow = builder.Window;
+
+Host = builder.Build();
+
+if (MainWindow.Content is not Frame rootFrame)
+{
+    rootFrame = new Frame();
+    MainWindow.Content = rootFrame;
+}
+
+if (rootFrame.Content == null)
+{
+    rootFrame.Navigate(typeof(MainPage), args.Arguments);
+}
+
+MainWindow.Activate();
 ```
+
+> [!IMPORTANT]
+> Be sure to remove any other code that sets `MainWindow` or `Window.Current` to prevent conflicts in your application.

doc/Learn/Authentication/AuthenticationOverview.md

@@ -14,6 +14,8 @@ There are two aspects to the Authentication extensions:
 
 `Authentication` is provided as an Uno Feature. To enable `Authentication` support in your application, add `Authentication` to the `<UnoFeatures>` property in the Class Library (.csproj) file. In case you are using Msal Authentication add `AuthenticationMsal`, or `AuthenticationOidc` for Oidc Authentication.
 
+[!include[existing-app](../includes/existing-app.md)]
+
 [!include[single-project](../includes/single-project.md)]
 
 For more information about `UnoFeatures` refer to our [Using the Uno.Sdk](xref:Uno.Features.Uno.Sdk) docs.

doc/Learn/Configuration/ConfigurationOverview.md

@@ -14,6 +14,8 @@ This feature uses [Microsoft.Extensions.Configuration](https://www.nuget.org/pac
 
 `Configuration` is provided as an Uno Feature. To enable `Configuration` support in your application, add `Configuration` to the `<UnoFeatures>` property in the Class Library (.csproj) file.
 
+[!include[existing-app](../includes/existing-app.md)]
+
 [!include[single-project](../includes/single-project.md)]
 
 For more information about `UnoFeatures` refer to our [Using the Uno.Sdk](xref:Uno.Features.Uno.Sdk) docs.

doc/Learn/Hosting/HostingOverview.md

@@ -7,6 +7,8 @@ uid: Uno.Extensions.Hosting.Overview
 
 Hosting is provided as an Uno Feature. To enable `Hosting` support in your application, add `Hosting` to the `<UnoFeatures>` property in the Class Library (.csproj) file. For more information about `UnoFeatures` refer to our [Using the Uno.Sdk](xref:Uno.Features.Uno.Sdk) docs.
 
+[!include[existing-app](../includes/existing-app.md)]
+
 [!include[single-project](../includes/single-project.md)]
 
 [!include[getting-help](../includes/getting-help.md)]

doc/Learn/Hosting/HowTo-HostingSetup.md

@@ -43,7 +43,24 @@ uid: Uno.Extensions.Hosting.HowToHostingSetup
     }
     ```
 
-### 3. Build the IHost
+### 3. Set Up the Main Window with the Builder
+
+* Replace `MainWindow = new Window()` or any `MainWindow` assignment with the `builder` approach:
+
+    ```cs
+    protected override void OnLaunched(LaunchActivatedEventArgs e)
+    {
+        var appBuilder = this.CreateBuilder(args)
+        .Configure(host => {
+            // Configure the host builder
+        });
+
+        MainWindow = builder.Window;
+        ...
+    }
+    ```
+
+### 4. Build the IHost
 
 * Finally, build the host and assign it to the `Host` property:
 
@@ -55,6 +72,8 @@ uid: Uno.Extensions.Hosting.HowToHostingSetup
             // Configure the host builder
         });
 
+        MainWindow = builder.Window;
+
         Host = appBuilder.Build();
         ...
     }

doc/Learn/Http/HttpOverview.md

@@ -11,6 +11,8 @@ For additional documentation on HTTP requests, read the references listed at the
 
 `Http` is provided as an Uno Feature. To enable `Http` support in your application, add `Http` to the `<UnoFeatures>` property in the Class Library (.csproj) file.
 
+[!include[existing-app](../includes/existing-app.md)]
+
 [!include[single-project](../includes/single-project.md)]
 
 For more information about `UnoFeatures` refer to our [Using the Uno.Sdk](xref:Uno.Features.Uno.Sdk) docs.

doc/Learn/Localization/LocalizationOverview.md

@@ -14,6 +14,8 @@ It uses [Microsoft.Extensions.Localization](https://www.nuget.org/packages/Micro
 
 `Localization` is provided as an Uno Feature. To enable `Localization` support in your application, add `Localization` to the `<UnoFeatures>` property in the Class Library (.csproj) file.
 
+[!include[existing-app](../includes/existing-app.md)]
+
 [!include[single-project](../includes/single-project.md)]
 
 For more information about `UnoFeatures` refer to our [Using the Uno.Sdk](xref:Uno.Features.Uno.Sdk) docs.

doc/Learn/Logging/LoggingOverview.md

@@ -15,6 +15,8 @@ It uses [Microsoft.Extensions.Logging](https://www.nuget.org/packages/Microsoft.
 
 `Logging` is provided as an Uno Feature. To enable `Logging` support in your application, add `Logging` to the `<UnoFeatures>` property in the Class Library (.csproj) file.
 
+[!include[existing-app](../includes/existing-app.md)]
+
 [!include[single-project](../includes/single-project.md)]
 
 For more information about `UnoFeatures` refer to our [Using the Uno.Sdk](xref:Uno.Features.Uno.Sdk) docs.

doc/Learn/Navigation/NavigationOverview.md

@@ -21,6 +21,8 @@ Navigation needs to encompass a range of UI concepts:
 
 `Navigation` is provided as an Uno Feature. To enable `Navigation` support in your application, add `Navigation` to the `<UnoFeatures>` property in the Class Library (.csproj) file.
 
+[!include[existing-app](../includes/existing-app.md)]
+
 [!include[single-project](../includes/single-project.md)]
 
 For more information about `UnoFeatures` refer to our [Using the Uno.Sdk](xref:Uno.Features.Uno.Sdk) docs.

doc/Learn/Serialization/SerializationOverview.md

@@ -12,6 +12,8 @@ uid: Uno.Extensions.Serialization.Overview
 
 `Serialization` is provided as an Uno Feature. To enable `Serialization` support in your application, add `Serialization` to the `<UnoFeatures>` property in the Class Library (.csproj) file.
 
+[!include[existing-app](../includes/existing-app.md)]
+
 [!include[single-project](../includes/single-project.md)]
 
 For more information about `UnoFeatures` refer to our [Using the Uno.Sdk](xref:Uno.Features.Uno.Sdk) docs.

doc/Learn/Storage/StorageOverview.md

@@ -23,6 +23,8 @@ Uno.Extensions.Storage facilitate local data storage across multiple platforms,
 </UnoFeatures>
 ```
 
+[!include[existing-app](../includes/existing-app.md)]
+
 [!include[single-project](../includes/single-project.md)]
 
 For more information about `UnoFeatures` refer to our [Using the Uno.Sdk](xref:Uno.Features.Uno.Sdk) docs.

doc/Learn/Validation/ValidationOverview.md

@@ -20,6 +20,8 @@ protected override void OnLaunched(LaunchActivatedEventArgs e){
 ...
 ```
 
+[!include[existing-app](../includes/existing-app.md)]
+
 By default, enabling validation will register the default `Validator` type with the DI container. This class implements `IValidator` and provides functionality to execute validation rules on validatable entities.
 
 ## Using the validation service

doc/Learn/includes/existing-app.md

@@ -0,0 +1,8 @@
+---
+uid: Uno.Extensions.ExistingApp
+---
+
+<!-- markdownlint-disable MD041 -->
+
+> [!IMPORTANT]
+> If your project doesn't have any of the Uno.Extension features set up yet, check out our [Installing Extensions in an existing project](xref:Uno.Extensions.HowToGettingStarted#installing-extensions-in-an-existing-project) docs to ensure you have all the necessary setup details.