Here's a comprehensive article on using PuppeteerSharp in Azure Functions to generate PDF invoices:

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In this article, we will explore how to create an ASP.NET Core Razor Pages app that uses PuppeteerSharp to render an invoice and generate a PDF. We'll also cover the process of creating an Azure Functions app and configuring it to run PuppeteerSharp.

A common use case for PuppeteerSharp is generating documents such as invoices, receipts, or reports. In this example, we will create a fictitious online store called Tailwind Traders and generate a PDF invoice using Razor templates.

To begin, let's create a new ASP.NET Core Web Application project using the `dotnet new webapp` command. This will give us a basic setup for our Razor Pages app.

Next, we'll need to install PuppeteerSharp in our project. We can do this by running the following NuGet package:

```

Install-Package PuppeteerSharp

```

Now that we have PuppeteerSharp installed, let's create a function that uses it to render the invoice and generate a PDF. This function will be responsible for rendering the Razor template and generating the PDF.

Here is an example of what this function might look like:

```csharp

using Microsoft.AspNetCore.Mvc;

using PuppeteerSharp;

public IActionResult GeneratePdfInvoice()

{

// Create a new instance of the browser

var browser = await PuppeteerSharp.LaunchAsync();

// Create a new page and navigate to the Razor template

var page = await browser.NewPageAsync();

await page.GoToAsync('https://example.com/invoice-template');

// Wait for the page to load

await page.WaitForLoadStateAsync(LoadState.NetworkIdle);

// Render the page as a PDF

using (var stream = new MemoryStream())

{

await page.PrintToPDFAsync(stream);

return File(stream.ToArray(), 'application/pdf', 'invoice.pdf');

}

```

In this example, we create a new instance of the browser using `PuppeteerSharp.LaunchAsync`. We then create a new page and navigate to our Razor template using `page.GoToAsync`.

Next, we wait for the page to load using `page.WaitForLoadStateAsync` before rendering it as a PDF using `page.PrintToPDFAsync`. The resulting PDF is saved to a memory stream and returned as a file response.

To run this function in Azure Functions, we'll need to create an Azure Functions app and configure it to use PuppeteerSharp. Here's how:

First, create a new Azure Functions app and select the 'HTTP trigger' template. This will give us a basic setup for our Azure Functions app.

Next, install the PuppeteerSharp NuGet package in our Azure Functions app using the following command:

```

Install-Package PuppeteerSharp

```

We'll also need to add a configuration file to our Azure Functions app to specify the path to our Razor template and other resources required to render the invoice. Here's an example of what this configuration file might look like:

```json

{

'razorTemplate': 'https://example.com/invoice-template',

'outputPath': 'output.pdf'

}

```

Finally, we'll need to update our Azure Functions app to use PuppeteerSharp and render the invoice as a PDF. Here's how:

First, create a new C# file in our Azure Functions app and add the following code:

```csharp

using Microsoft.Azure.Functions.Worker;

using PuppeteerSharp;

public static async Task GeneratePdfInvoice(

'HttpTrigger(AuthorizationLevel.Function, 'get', Route = null)' HttpRequestData req)

{

// Get the configuration settings

var config = Config.GetSection('PuppeteerSharp');

// Create a new instance of the browser

var browser = await PuppeteerSharp.LaunchAsync();

// Create a new page and navigate to the Razor template

var page = await browser.NewPageAsync();

await page.GoToAsync(config''razorTemplate'');

// Wait for the page to load

await page.WaitForLoadStateAsync(LoadState.NetworkIdle);

// Render the page as a PDF

using (var stream = new MemoryStream())

{

await page.PrintToPDFAsync(stream);

return req.CreateResponse((int)HttpStatusCode.OK, 'application/pdf', config''outputPath'', stream.ToArray());

}

```

In this example, we get the configuration settings from our Azure Functions app and create a new instance of the browser using `PuppeteerSharp.LaunchAsync`. We then create a new page and navigate to our Razor template using `page.GoToAsync`.

That's it! With these steps, you should now have an Azure Functions app that uses PuppeteerSharp to render a Razor template and generate a PDF invoice.

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