.NET MAUI: problem open Image File from Resources\Images\some_image.png

Question

I need to pass a local / project Image as a Base64String to an API. This approach:

string imagePath = "Resources/Images/dotnet_bot.png";
byte[] imageBytes = File.ReadAllBytes(imagePath);
string base64String = Convert.ToBase64String(imageBytes);
return base64String;

produces following exception:

Could not find a part of the path '/Resources/Images/dotnet_bot.png'.

Another approach:

using var imageEncodeStream = await FileSystem.OpenAppPackageFileAsync("dotnet_bot.png");
using (var memoryStream = new MemoryStream())
{
    imageEncodeStream.CopyTo(memoryStream);
    return Convert.ToBase64String(memoryStream.ToArray());
}

produces

File not found exception

Could somebode help me please?

Answer 1

The official document about the FileSystem.OpenAppPackageFileAsync said:

FileSystem.OpenAppPackageFileAsync

Files that were added to the project with the Build Action of MauiAsset can be opened with this method. .NET MAUI projects will process any file in the Resources\Raw folder as a MauiAsset. The FileSystem.OpenPackageFileAsync method can't get the length of the stream on Android by accessing the Result.Length property. Instead, you have to read the whole stream and count how many bytes there are to get the size of the asset.

And the Resources/Images/dotnet_bot.png's build action is MauiImage not MauiAsset. So you get the error.

Update:

The full code in the csproj:

<Project Sdk="Microsoft.NET.Sdk">

      <PropertyGroup>
            <TargetFrameworks>net8.0-android;net8.0-ios;net8.0-maccatalyst</TargetFrameworks>
            <TargetFrameworks Condition="$([MSBuild]::IsOSPlatform('windows'))">$(TargetFrameworks);net8.0-windows10.0.19041.0</TargetFrameworks>
            <!-- Uncomment to also build the tizen app. You will need to install tizen by following this: https://github.com/Samsung/Tizen.NET -->
            <!-- <TargetFrameworks>$(TargetFrameworks);net8.0-tizen</TargetFrameworks> -->

            <!-- Note for MacCatalyst:
            The default runtime is maccatalyst-x64, except in Release config, in which case the default is maccatalyst-x64;maccatalyst-arm64.
            When specifying both architectures, use the plural <RuntimeIdentifiers> instead of the singular <RuntimeIdentifier>.
            The Mac App Store will NOT accept apps with ONLY maccatalyst-arm64 indicated;
            either BOTH runtimes must be indicated or ONLY macatalyst-x64. -->
            <!-- For example: <RuntimeIdentifiers>maccatalyst-x64;maccatalyst-arm64</RuntimeIdentifiers> -->

            <OutputType>Exe</OutputType>
            <RootNamespace>MauiApp3</RootNamespace>
            <UseMaui>true</UseMaui>
            <SingleProject>true</SingleProject>
            <ImplicitUsings>enable</ImplicitUsings>
            <Nullable>enable</Nullable>

            <!-- Display name -->
            <ApplicationTitle>MauiApp3</ApplicationTitle>

            <!-- App Identifier -->
            <ApplicationId>com.companyname.mauiapp3</ApplicationId>

            <!-- Versions -->
            <ApplicationDisplayVersion>1.0</ApplicationDisplayVersion>
            <ApplicationVersion>1</ApplicationVersion>

            <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'ios'">11.0</SupportedOSPlatformVersion>
            <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'maccatalyst'">13.1</SupportedOSPlatformVersion>
            <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'android'">21.0</SupportedOSPlatformVersion>
            <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'windows'">10.0.17763.0</SupportedOSPlatformVersion>
            <TargetPlatformMinVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'windows'">10.0.17763.0</TargetPlatformMinVersion>
            <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'tizen'">6.5</SupportedOSPlatformVersion>
      </PropertyGroup>

      <ItemGroup>
            <!-- App Icon -->
            <MauiIcon Include="Resources\AppIcon\appicon.svg" ForegroundFile="Resources\AppIcon\appiconfg.svg" Color="#512BD4" />

            <!-- Splash Screen -->
            <MauiSplashScreen Include="Resources\Splash\splash.svg" Color="#512BD4" BaseSize="128,128" />

            <!-- Images -->
            <MauiImage Include="Resources\Images\*" />

            <!-- Custom Fonts -->
            <MauiFont Include="Resources\Fonts\*" />

            <!-- Raw Assets (also remove the "Resources\Raw" prefix) -->
            <MauiAsset Include="Resources\Raw\**" LogicalName="%(RecursiveDir)%(Filename)%(Extension)" />
            <MauiAsset Include="Resources\Images\**" LogicalName="%(RecursiveDir)%(Filename)%(Extension)" />

      </ItemGroup>

      <ItemGroup>
            <PackageReference Include="Microsoft.Maui.Controls" Version="$(MauiVersion)" />
            <PackageReference Include="Microsoft.Maui.Controls.Compatibility" Version="$(MauiVersion)" />
            <PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="8.0.0" />
      </ItemGroup>

      <ItemGroup>
        <MauiImage Update="Resources\Images\dotnet_bot.png" Resize="True" BaseSize="300,185" />
      </ItemGroup>

</Project>

And the result image: