Step by Step Guide to Building a pdfFiller API Integration in C#

Aug 16, 2024 • 5 minute read

Introduction

Hey there, fellow developer! Ready to supercharge your C# application with some PDF magic? Let's dive into integrating the pdfFiller API. This powerful tool will let you manipulate PDFs like a pro, all from within your C# code. Buckle up!

Prerequisites

Before we jump in, make sure you've got:

Visual Studio (or your favorite C# IDE)
.NET Core 3.1 or later
A pdfFiller API account (grab those credentials!)

Setting up the project

First things first, let's get our project off the ground:

Fire up Visual Studio and create a new C# project.

Time for some NuGet goodness. Install these packages:

Install-Package Newtonsoft.Json
Install-Package RestSharp

Authentication

Now, let's tackle authentication. pdfFiller uses OAuth 2.0, so we'll need to implement that:

public async Task<string> GetAccessToken()
{
    var client = new RestClient("https://api.pdffiller.com/v1/oauth/token");
    var request = new RestRequest(Method.POST);
    request.AddParameter("grant_type", "client_credentials");
    request.AddParameter("client_id", "YOUR_CLIENT_ID");
    request.AddParameter("client_secret", "YOUR_CLIENT_SECRET");

    var response = await client.ExecuteAsync(request);
    var token = JsonConvert.DeserializeObject<TokenResponse>(response.Content);
    return token.AccessToken;
}

Pro tip: Store that access token securely and reuse it until it expires!

Core API Integration

Document Upload

Let's get that PDF uploaded:

public async Task<string> UploadDocument(string filePath)
{
    var client = new RestClient("https://api.pdffiller.com/v1/document");
    var request = new RestRequest(Method.POST);
    request.AddHeader("Authorization", $"Bearer {accessToken}");
    request.AddFile("file", filePath);

    var response = await client.ExecuteAsync(request);
    var result = JsonConvert.DeserializeObject<UploadResponse>(response.Content);
    return result.Id;
}

Fill PDF Form

Time to fill in those forms:

public async Task FillForm(string documentId, Dictionary<string, string> formData)
{
    var client = new RestClient($"https://api.pdffiller.com/v1/document/{documentId}/fill");
    var request = new RestRequest(Method.POST);
    request.AddHeader("Authorization", $"Bearer {accessToken}");
    request.AddJsonBody(formData);

    await client.ExecuteAsync(request);
}

Document Retrieval

Let's grab that filled PDF:

public async Task<byte[]> GetFilledDocument(string documentId)
{
    var client = new RestClient($"https://api.pdffiller.com/v1/document/{documentId}/download");
    var request = new RestRequest(Method.GET);
    request.AddHeader("Authorization", $"Bearer {accessToken}");

    var response = await client.ExecuteAsync(request);
    return response.RawBytes;
}

Error Handling and Logging

Don't forget to wrap your API calls in try-catch blocks and log those responses:

try
{
    // API call here
}
catch (Exception ex)
{
    Logger.LogError($"API call failed: {ex.Message}");
    // Handle the error appropriately
}

Optimizations

To keep things speedy:

Cache your access token
Implement exponential backoff for rate limiting

Testing

Unit test those key components and integration test your API calls. Trust me, your future self will thank you!

Security Considerations

Remember:

Never hardcode your API keys
Always use HTTPS for API calls
Encrypt sensitive data at rest

Conclusion

And there you have it! You've just built a solid pdfFiller API integration in C#. Pretty cool, right? From here, sky's the limit. Maybe try implementing some advanced features or optimizing your code further.

Resources

Now go forth and conquer those PDFs! Happy coding!