Issues to call the event

Many thanks. How about the issues below?

due to App.xaml file below

Based on your screenshot, the App.xaml content itself looks correct for a .NET MAUI app. The errors about Application and ResourceDictionary usually mean Visual Studio is not treating this file as MAUI XAML.

Please check the following:

1. In App.xaml Properties, make sure Build Action is set to MauiXaml.
2. In the project file, confirm <UseMaui>true</UseMaui> is present.
3. Clean the project, then delete the bin and obj folders, and rebuild.
4. Make sure the .NET MAUI workload is installed in Visual Studio.

If Build Action is not MauiXaml, Visual Studio may show exactly this kind of error even when the XAML syntax is correct.

So in this case, I would check the file properties and project configuration first, rather than changing the App.xaml content.

Where is Build Action in App.xaml Properties?

Select App.xaml in Solution Explorer, then press F4 to open the Properties window. In that window, look for the Build Action field and check whether it is set to MauiXaml. If you do not see Build Action, make sure App.xaml itself is selected, not the project node or the editor tab.

Anything wrong in red below (not much details are shown)?

Any help?

Based on your screenshot, nothing is obviously wrong in the red area itself. It only shows that the Properties window is not displaying useful details for App.xaml.

So the next step is not to change that red area.

Please try this instead:

1. Right-click App.xaml in Solution Explorer.
2. Select Properties.
3. Check whether Build Action is set to MauiXaml.

If Build Action is still not shown there, then please open the project .csproj file and confirm this line exists:

<UseMaui>true</UseMaui>

I've done these:

1. Right-click App.xaml in Solution Explorer.
2. Select Properties.

but only get this

I then edited the project file and get this in the file:

<UseMaui>true</UseMaui>

How to resolve the current issues on the project?

Can you add as much as details and information so I can understand what errors you are currently facing?

I cannot do the 3rd step below as I only get the above screen (after having done 1st 2 steps below). I was being stuck on it.

1. Right-click App.xaml in Solution Explorer.
2. Select Properties.
3. Check whether Build Action is set to MauiXaml.

Thanks for the additional details.

Looking at the full thread as a whole, this no longer looks like a single App.xaml issue. The screenshots suggest the project has entered an inconsistent XAML state after several test changes, for example:

• a page file was added as UI_0.cs without a matching XAML page
• another file was created as ContentView instead of a page
• later, unrelated MAUI XAML types in App.xaml also stopped resolving

So at this point, I would not continue troubleshooting the blank Properties page itself.

Instead, I would suggest isolating whether the problem is in this project or in the local MAUI/Visual Studio environment:

1. Create a brand-new blank .NET MAUI App project in Visual Studio.
2. Build it immediately without adding any extra files.
3. If the new project builds successfully, then the current project is likely corrupted or misconfigured by the earlier test file changes.
4. If the new project shows the same XAML errors, then this points more strongly to a Visual Studio or MAUI tooling problem on the machine.

If the new blank MAUI project works, I would recommend reverting the temporary test pages in the current project and then re-adding the page from a clean MAUI page template.

If the new blank MAUI project does not work, then the next step would be to repair the Visual Studio installation or the MAUI workload, because the issue would no longer be specific to your project files.

I re-create the project well and is able to run it. How to ensure it would show the content view below when running it?

Good day,

Can you help?

Thanks for the update.

If NewContent1.xaml was created as a ContentView, it will not appear by itself when the app starts. A ContentView must be placed inside a page, such as MainPage.xaml.

So to show that content when running the app, you can place it inside MainPage.xaml, for example:

<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:MauiApp10_1"
             x:Class="MauiApp10_1.MainPage">

    <local:NewContent1 />

</ContentPage>

If you want the new UI to be a full screen by itself, then create it as a ContentPage instead of a ContentView.

So in short:

• use ContentView if it will be embedded inside another page
• use ContentPage if it should be shown directly as a screen when the app runs

Please also note that any code snippets I provide are for reference only and may need to be adjusted to match your project structure and naming before using them directly.

If my explanation was helpful to you so far, I would greatly appreciate it if you could follow the instructions here.

If you have new questions, kindly post them on this platform so I can support you better.

Sorry, do you mean it is fine to make the content page below be the main page or not?

Since the screenshot shows a ContentPage, it is fine to make that page the main page.

For example, in App.xaml.cs, you can set:

public App()
{
    InitializeComponent();
    MainPage = new NewPage2();
}

So for the page shown in your screenshot, yes, it can be displayed directly when the app starts.

Sorry, I put it and got the issue like

The error in your screenshot is because MainPage = new NewPage2(); was added inside NewPage2.xaml.cs.

That line should not be placed inside the page constructor.

Please move it to App.xaml.cs instead.

For example:

public App()
{
    InitializeComponent();
    MainPage = new NewPage2();
}

In NewPage2.xaml.cs, keep only the page logic, for example:

public NewPage2()
{
    InitializeComponent();
}

So yes, NewPage2 can be the startup page, but the MainPage assignment must be done in App.xaml.cs, not in NewPage2.xaml.cs.

Please also note that any code snippets I provide are for reference only and may need to be adjusted to match your project structure and naming before using them directly.

Yes, I put that to App.xampl.cs and then re-run the project but the Content page was not shown

Any other help?

If NewPage2 still does not appear after you changed App.xaml.cs, then the next thing to check is whether your project is using AppShell.xaml.

In many .NET MAUI projects, the startup UI is controlled by AppShell, for example:

public App()
{
    InitializeComponent();
    MainPage = new AppShell();
}

If your current App.xaml.cs still points to AppShell, then NewPage2 will not be shown at startup.

To test NewPage2 directly, update App.xaml.cs to:

public App()
{
    InitializeComponent();
    MainPage = new NewPage2();
}

Also make sure NewPage2.xaml.cs still contains the correct constructor:

public NewPage2()
{
    InitializeComponent();
}

So in this case, I would double-check whether App.xaml.cs is still loading AppShell instead of NewPage2.

Please also note that any code snippets I provide are for reference only and may need to be adjusted to match your project structure and naming before using them directly.

There is now Appshell.xaml file on the project. Any way to show NewPage2 on the project? Anything unclear to this? Need more details (or the project)?

For this step, I do not need the full project yet.

If you already updated the startup page as mentioned earlier and NewPage2 still does not appear, then the next useful detail would be:

1. the current contents of App.xaml.cs
2. the current contents of NewPage2.xaml
3. the current contents of NewPage2.xaml.cs

That should be enough to check whether the page is wired correctly. You can screenshot the contents.

FYI

The screenshots help clarify the issue.

There are two separate points here:

1. In App.xaml.cs, your app is currently starting from:

return new Window(new AppShell());

So even if you changed MainPage earlier, that would not control startup in this project, because CreateWindow(...) is what is being used.

2. NewContent2 is currently a ContentView, not a ContentPage.

A ContentView cannot be shown directly as the startup screen.

So to show it when the app runs, you have two options:

1. Change NewContent2 to a ContentPage, then return that page from CreateWindow(...).
2. Keep NewContent2 as a ContentView, but place it inside a page such as MainPage or another ContentPage.

For your current project, the most direct test would be:

• change NewContent2 from ContentView to ContentPage
• then update App.xaml.cs so that CreateWindow(...) returns that page instead of AppShell

For example:

protected override Window CreateWindow(IActivationState? activationState)
{
  return new Window(new NewContent2());
}

So based on your screenshots, the reason it is not shown is not unclear anymore:

• the app is still starting with AppShell
• and NewContent2 is not a page yet

Please also note that any code snippets I provide are for reference only and may need to be adjusted to match your project structure and naming before using them directly.

I did the change like

Try to rebuild it but cannot locate the issue.

Any other help?

Thanks for the screenshot.

The change in App.xaml.cs looks reasonable. This part:

return new Window(new NewPage1());

is a valid way to start the app with NewPage1.

So the current blocker does not appear to be CreateWindow(...) anymore.

From the build output in your screenshot, the actual failure is now in App.xaml:

• Unknown type 'Application'
• Unknown type 'ResourceDictionary'

That means the project is still not recognizing App.xaml as MAUI XAML correctly, so the app cannot build yet even though the startup page code was changed.

I also noticed that in App.xaml.cs, InitializeComponent(); is currently commented out. If App.xaml is still present in the project, that line should normally remain enabled:

public App()
{
  InitializeComponent();
}

So at this point, I would focus on App.xaml rather than NewPage1.

The next useful details would be:

1. the full contents of App.xaml
2. the full contents of App.xaml.cs
3. the relevant .csproj section that includes <UseMaui>true</UseMaui>

Based on this screenshot alone, the startup page change looks fine. The current issue is that App.xaml is still failing to compile.

Please also note that any code snippets I provide are for reference only and may need to be adjusted to match your project structure and naming before using them directly.

I get the issue below when I enabled "Initialize..." line

The new error helps clarify the issue further.

InitializeComponent(); itself is not the root problem here.

If Visual Studio says:

The name 'InitializeComponent' does not exist in the current context

that usually means the generated code from App.xaml was not created successfully.

So this is still pointing back to the same underlying issue: App.xaml is not being compiled as MAUI XAML correctly.

The change in App.xaml.cs looks reasonable. This part:

return new Window(new NewPage1());

is a valid way to start the app with NewPage1.

So the current blocker is still App.xaml, not NewPage1.

When App.xaml is compiled correctly, this constructor should work:

public App()
{
  InitializeComponent();
}

But right now it cannot work because the App.xaml generated file is missing.

The next useful details would be:

1. the full contents of App.xaml
2. the full contents of App.xaml.cs
3. the relevant .csproj section that includes <UseMaui>true</UseMaui>

Based on this screenshot alone, the startup page change looks fine. The current issue is that App.xaml is still failing to generate its code-behind correctly.

Please also note that any code snippets I provide are for reference only and may need to be adjusted to match your project structure and naming before using them directly.

I shared the files below for you.

Any help?

Thanks for sharing the files.

The files look mostly correct.

At this point, I would suggest:

1. Open the new MAUI project that builds correctly.
2. Copy its default App.xaml and App.xaml.cs.
3. Replace the current App.xaml and App.xaml.cs in your project.
4. Build the project again.
5. If it builds, then add back your CreateWindow(...) change for NewPage1.

So the main issue now looks like the current App.xaml pair, not NewPage1.

Thanks a lot. Do we need a totally new project or not?

Thanks for the update.

No, you do not need a totally new project.

You can keep the current project and just copy the clean App.xaml and App.xaml.cs from the new working MAUI project into this one.

Then build again. If it works, add back your CreateWindow(...) change for NewPage1.

I used your suggested way but it was not OK due to these

The name 'InitializeComponent' does not exist in the current context

The type or namespace name 'AppShell' could not be found (are you missing a using directive or an assembly reference?)

...

If you already copied the clean App.xaml and App.xaml.cs and still get:

• InitializeComponent does not exist
• AppShell could not be found

then the current project is likely still broken at the project/XAML generation level.

At this point, the simpler fix is to use the new working MAUI project as the base project.

In other words:

1. Keep the new MAUI project that builds successfully.
2. Move your pages, code-behind files, and other custom code into that new project.
3. If you do not want AppShell, remove its reference from App.xaml.cs and use your NewPage1 in CreateWindow(...).

Yes, I create another new project and can run it. I can show the page with button but how to ensure the event is being run well per the following?

From your screenshots, the event wiring looks correct:

• NewPage1.xaml uses Clicked="OnButtonClicked"
• NewPage1.xaml.cs contains OnButtonClicked(object sender, EventArgs e)

To confirm the event is running, the simplest test is to put a small check at the start of OnButtonClicked, for example:

private async void OnButtonClicked(object sender, EventArgs e)
{
  await DisplayAlert("Test", "Button click event is running.", "OK");
}

If the message appears when you click the button, then the event is working correctly.

After that, you can put your DownloadAndShareFileAsync(...) code back inside the same method.

Please note that the code snippet above is for reference only and may need to be adjusted to fit your current project structure.

Jack,

I will check this and revert. Many thanks.

Yes, I put the test message and can see that. Suppose everything is running well there, how to locate any output file per the code below?

There is a significant gap between the code you are using and the question you are asking.

The structure of your code actually answers your own question, which suggests you are piecing together snippets without a clear understanding of their function. You've defined a localPath variable—view your code! You've also defined a fileStream variable—review the code! You are the one who told the program exactly where to put the file.

Before moving forward, please explain to the community exactly what problem you are trying to solve. Are you trying to save a file to a location where the user can find it later (like a Downloads folder), or are you trying to send a file to another app? Once you define your intent, we can help you with the correct architecture, but right now you are using a "Send" command to perform a "Save" function while ignoring the variables you've already defined.

Yes, it was to save the file like

Where to find the file out?

There is a significant gap between the code you are using and the question you are asking.

The structure of your code answers your own question. You defined localPath in the very first line using FileSystem.CacheDirectory. The file is exactly where you told the program to put it. Asking the community to "locate" a file when the variable is defined right in front of you suggests you are copying snippets without making any effort to understand them.

If this is a mobile application, you need to understand how CacheDirectory works: This is a private, sandboxed directory. On Android and iOS, files in the cache are invisible to the user and cannot be found using the device's File Explorer. It is a temporary "scratchpad" for the app, not a storage location for a user to "locate" later.

The original issue in this thread seemed to be a lack of understanding regarding how to add a page to a MAUI application and handle a click event. That is a fundamental UI task that has nothing to do with your latest question about file paths.

At the very least, you should try reading the openly published .NET MAUI documentation to understand the code you are copying from the internet. Furthermore, your code assumes the REST call was successful; the file will only exist if your response actually returned data. If you did not write this code, you should contact the person who provided it for an explanation. It is not a productive use of the community's time to troubleshoot logic when the information is already in your possession.

Since this question is entirely different from the original and this thread is now dozens of responses deep, you should start a new question if you need help understanding how the FileSystem namespace works in .NET.

Please clarify your intent in that new thread (assuming the REST call works):

To Share: Use the localPath variable you already have.

To Save for the user: You must use the Community Toolkit FileSaver. You cannot save a file to a hidden internal cache and then expect the user to find it.