Solving Blazor WebAssembly Error: Cannot read properties of undefined (reading ‘out’)

Are you tired of encountering the frustrating “Cannot read properties of undefined (reading ‘out’)” error after publishing your Blazor WebAssembly application? You’re not alone! This error can be a showstopper, but don’t worry, we’ve got you covered.

What causes this error?

The error typically occurs when the JavaScript runtime attempts to read the ‘out’ property from an undefined object. This can happen due to various reasons, such as:

• Incorrectly configured or missing JavaScript files
• Invalid or corrupted WebAssembly modules
• Incompatible or outdated dependencies
• Misconfigured environment or build settings

Step-by-Step Solution

Don’t panic! Follow these steps to resolve the issue and get your Blazor WebAssembly app up and running:

Step 1: Verify JavaScript Files

Ensure that the required JavaScript files are present and correctly configured in your project:

1. Check if the ‘_framework’ folder is present in your project directory.
2. Verify that the ‘blazor.webassembly.js’ file is present inside the ‘_framework’ folder.
3. Make sure the ‘blazor.boot.json’ file is correctly configured and points to the correct WebAssembly module.

// Sample blazor.boot.json file
{
  "assemblyName": "MyBlazorApp",
  "moduleName": "MyBlazorApp.dll",
  "launchUrl": "/"
}

Step 2: Validate WebAssembly Modules

Ensure that your WebAssembly modules are correctly built and not corrupted:

1. Verify that the ‘.wasm’ files are present in the ‘_framework’ folder.
2. Check the timestamp of the ‘.wasm’ files to ensure they are up-to-date.
3. Try re-building your WebAssembly modules by running the following command:

dotnet publish -c Release

Step 3: Update Dependencies

Ensure that your dependencies are compatible and up-to-date:

1. Verify that you are using the latest version of the Microsoft.AspNetCore.Components.WebAssembly NuGet package.
2. Check for any other outdated or incompatible dependencies in your project.
3. Update your dependencies by running the following command:

dotnet restore

Step 4: Configure Environment and Build Settings

Verify that your environment and build settings are correctly configured:

1. Check your `csproj` file for any incorrect or outdated settings.
2. Verify that the `false` setting is present and set to `false`.
3. Ensure that the `true` setting is present and set to `true`.

// Sample csproj file
<Project Sdk="Microsoft.NET.Sdk.Web">
  <PropertyGroup>
    <TargetFramework>net5.0</TargetFramework>
    <WebAssemblyEnableP_Invoke>false</WebAssemblyEnableP_Invoke>
    <BlazorWebAssemblyEnableLazyLoading>true</BlazorWebAssemblyEnableLazyLoading>
  </PropertyGroup>
  ...
</Project>

Troubleshooting Tips

If you’re still encountering issues, try the following troubleshooting tips:

Troubleshooting Tip	Description
Clear cache and reload	Clear your browser’s cache and reload the application to ensure that the latest changes are applied.
Check browser console	Inspect the browser console for any error messages that may provide additional insights into the issue.
Verify WebAssembly module loading	Use the browser’s developer tools to verify that the WebAssembly modules are correctly loaded and initialized.

Conclusion

The “Cannot read properties of undefined (reading ‘out’)” error can be frustrating, but by following these steps and troubleshooting tips, you should be able to resolve the issue and get your Blazor WebAssembly application up and running.

Remember to double-check your JavaScript files, WebAssembly modules, dependencies, and environment settings to ensure that everything is correctly configured and up-to-date.

If you’re still encountering issues, don’t hesitate to seek help from the Blazor community or try debugging your application with more advanced tools and techniques.

Additional Resources

For more information and resources on Blazor WebAssembly, check out the following links:

• Blazor WebAssembly Hosting Models
• Blazor Troubleshooting
• ASP.NET Core GitHub Issues

By following this comprehensive guide, you should be able to resolve the “Cannot read properties of undefined (reading ‘out’)” error and get your Blazor WebAssembly application running smoothly.

Happy coding!

Frequently Asked Question

Are you stuck with the infamous “Cannot read properties of undefined (reading ‘out’)” error after publishing your Blazor WebAssembly application?