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C# try catch finally (How It Works For Developers)

Jordi Bardia
Jordi Bardia
October 23, 2024
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Introduction

Error handling is a fundamental aspect of robust application development. In C#, the try-catch-finally blocks are powerful tools that ensure your application can handle unexpected situations gracefully without crashing. Effective error handling not only helps in managing runtime errors but also in maintaining the stability and reliability of your applications.

IronPDF is a comprehensive PDF library for .NET that simplifies PDF creation, manipulation, and rendering. When integrating IronPDF into your .NET projects, understanding how to use error handling effectively is crucial for building reliable PDF-based applications. In today's article, we will be looking at how a try catch finally statement can be implemented into your IronPDF projects for better exception handling, and how this can improve the efficiency and performance of your PDF workspace.

Understanding Try, Catch, and Finally in C#

What is a Try-Catch block?

In C#, the try-catch block allows you to handle exceptions that occur during the execution of your code. The try block section contains the code that might throw an exception, while the catch block handles the exception if it occurs. This structure is essential for preventing application crashes, avoiding letting exceptions propagate up the call stack, and providing a way to handle errors gracefully. Without proper error handling, exceptions can cause abrupt application crashes, so utilizing the try-catch block can be essential to preventing this by handling the exceptions gracefully.

The try block is where you place any code that might potentially throw an exception. This block serves as a safeguard, enabling your to specify a section of code that should be monitored for errors. If any parts of the try block throw exceptions, control of it is immediately transferred to the corresponding catch block.

The catch block follows the try block and is used to handle exceptions thrown by the try block code. You don't have to restrict yourself to just one catch block, you can have multiple catch blocks set up to handle different potential types of exceptions separately. Each catch block specifies the type of exception it handles and contains the code to process the exception, such as logging the error or displaying a user-friendly message about the error.

using IronPdf;
public static void Main(string[] args)
    {
        try
        {
            ChromePdfRenderer renderer = new ChromePdfRenderer();
            var pdf = renderer.RenderHtmlFileAsPdf("Example.html");
            pdf.SaveAs("output.pdf");
        }
        catch (FileNotFoundException ex)
        {
        // Handle file not found exception
            Console.WriteLine("File not found: " + ex.Message);
        }
    catch (UnauthorizedAccessException ex)
    {
            // Handle unauthorized access exception
            Console.WriteLine("Error: Access to the file is denied. " + ex.Message);
    }
        catch (Exception ex)
        {
        // Handle any other exceptions
            Console.WriteLine("An unexpected error occurred: " + ex.Message);
        }
     }
using IronPdf;
public static void Main(string[] args)
    {
        try
        {
            ChromePdfRenderer renderer = new ChromePdfRenderer();
            var pdf = renderer.RenderHtmlFileAsPdf("Example.html");
            pdf.SaveAs("output.pdf");
        }
        catch (FileNotFoundException ex)
        {
        // Handle file not found exception
            Console.WriteLine("File not found: " + ex.Message);
        }
    catch (UnauthorizedAccessException ex)
    {
            // Handle unauthorized access exception
            Console.WriteLine("Error: Access to the file is denied. " + ex.Message);
    }
        catch (Exception ex)
        {
        // Handle any other exceptions
            Console.WriteLine("An unexpected error occurred: " + ex.Message);
        }
     }

Example of a FileNotFoundException

C# try catch finally (How It Works For Developers): Figure 1 - FileNotFoundException Console Output

The Role of the Finally Block

The finally block is used to execute code that must run regardless of whether an exception object was thrown or not. This is typically used for cleaning up resources, such as closing file streams or database connections, ensuring that these resources are released properly. The code inside a finally block is always executed, regardless of any errors thrown in the try block, making it ideal for tasks that need to be performed no matter what happens in the try block.

By ensuring that cleanup code is always executed, the finally block helps maintain application stability and prevents resource exhaustion. For example, if you were working with a database and a database connection was left open, it might prevent other parts of the application from functioning correctly or could exhaust the connection pool. Or, when working with file streams, its critical to close file streams to free up system resources. The finally block ensures that the file stream is closed whether the file operations succeed or fail, as long as you have put the code for closing the file stream in the finally block.

public static void Main(string[] args)
    {
        try
        {
            int num = 10;
            int result = num / 0;
        }
        catch (Exception ex)
        {
            Console.WriteLine("Cannot divide by zero. " + ex.Message);
        }
        finally 
        { 
            // This finally block executes regardless of whether an exception was thrown
            Console.WriteLine("Cleanup code runs here");
        }
    }
public static void Main(string[] args)
    {
        try
        {
            int num = 10;
            int result = num / 0;
        }
        catch (Exception ex)
        {
            Console.WriteLine("Cannot divide by zero. " + ex.Message);
        }
        finally 
        { 
            // This finally block executes regardless of whether an exception was thrown
            Console.WriteLine("Cleanup code runs here");
        }
    }

C# try catch finally (How It Works For Developers): Figure 2

An example of the flow of the try-catch-finally block within a program could look like this:

C# try catch finally (How It Works For Developers): Figure 3

Implementing Try-Catch-Finally with IronPDF

Setting Up IronPDF in Your Project

To begin using the IronPDF library in your .NET projects, you will first need to install it via the NuGet Package Manager. One way to do this is by navigating to tools > NuGet Package Manager > NuGet Package Manager for Solution and searching IronPDF:

C# try catch finally (How It Works For Developers): Figure 4

Or, Alternatively running the following command in the Package Manager Console:

Install-Package IronPdf
Install-Package IronPdf

To begin using IronPDF in your code, ensure you have placed the `using IronPdf` statement at the top of your code file. For a more in-depth guide to setting up IronPDF in your environment, check out the getting started page.

Handling Exceptions in PDF Generation

When working with IronPDF to generate PDFs, it’s crucial to anticipate and handle various exceptions that might arise during the process. Proper implementation of exception handling code not only prevents your application from crashing but also provides a way to respond to errors gracefully, improving the overall robustness and user experience of your application. Some common exceptions that may be thrown include:

  • FileNotFound: This exception occurs when you try to load a file with IronPDF that does not exist on the specified file path. One way of handling this could be using `File.Exists(path)` the verify the files existence, or wrapping the operation in a If statement block to check if the file exists.
  • InvalidOperationsException: This occurs when the state of the PDF document is invalid for the current operation. For example, if you try to perform operations on a PDF that is not fully loaded or rendered.
  • UnauthorizedAccessException: This exception occurs when the application doesn't have permission to access the specified file or directory. This can happen due to restrictive file permissions or attempting to write to a read-only file. For example, if you were to try writing output PDF files to a directory where the application lacks writing permissions.

Some IronPDF specific exception class types include:

  • IronPdfAssemblyVersionMismatchException: This refers to errors that occur while you are loading assemblies during IronPDF deployment.
  • IronPdfNativeException: This represents the errors that can occur in the IronPDF native code.
  • IronPdfProductException: This represents any errors that may occur during IronPDF execution.
using IronPdf;
using IronPdf.Exceptions;
public static void Main(string[] args)
{
    try
    {
    IronPdf.License.LicenseKey = "license-key";
        ChromePdfRenderer renderer = new ChromePdfRenderer();
        // Generate PDF from HTML
        var pdf = renderer.RenderHtmlAsPdf("<h1>Hello, World!</h1>");
        pdf.SaveAs("output.pdf");
    }
    catch (IronPdfProductException ex)
    {
        // Handle PDF generation specific exceptions
        Console.WriteLine("Error During IronPDF execution: " + ex.Message);
    }
    catch (Exception ex)
    {
        // Handle general exceptions
        Console.WriteLine("An unexpected error occurred: " + ex.Message);
    }
}
using IronPdf;
using IronPdf.Exceptions;
public static void Main(string[] args)
{
    try
    {
    IronPdf.License.LicenseKey = "license-key";
        ChromePdfRenderer renderer = new ChromePdfRenderer();
        // Generate PDF from HTML
        var pdf = renderer.RenderHtmlAsPdf("<h1>Hello, World!</h1>");
        pdf.SaveAs("output.pdf");
    }
    catch (IronPdfProductException ex)
    {
        // Handle PDF generation specific exceptions
        Console.WriteLine("Error During IronPDF execution: " + ex.Message);
    }
    catch (Exception ex)
    {
        // Handle general exceptions
        Console.WriteLine("An unexpected error occurred: " + ex.Message);
    }
}

Output

An example of exception handling with IronPDF could be that the license key is wrong, or missing. In that case, IronPdfProductException, if being used as part of the exception handling process, would be used to show the matching error message.

C# try catch finally (How It Works For Developers): Figure 5

Cleaning Up Resources with Finally Block

In scenarios involving file operations or resource management, the finally block ensures that all resources are released appropriately, even if an error occurs during the process.

When working with files, it's common to open a file stream for reading or writing. If an exception occurs while processing the file, failing to close the stream could leave the file locked or cause other issues. The finally block ensures the file stream is always closed, thus releasing the resource.

public static void Main(string[] args)
{
    try
    {
        ChromePdfRenderer renderer = new ChromePdfRenderer();
        // Generate PDF from HTML
        var pdf = renderer.RenderHtmlAsPdf("<h1>Hello, World!</h1>");
        pdf.SaveAs("output.pdf");
    }
    catch (IronPdf.Exceptions.IronPdfProductException ex)
    {
        // Handle PDF generation specific exceptions
        Console.WriteLine("Error During IronPDF execution: " + ex.Message);
    }
    catch (Exception ex)
    {
        // Handle general exceptions to avoid any unhandled exception issues
        Console.WriteLine("An unexpected error occurred: " + ex.Message);
    }
    finally
    {
        // Cleanup resources if necessary
        if (fileStream != null)
        {
            fileStream.Close();
            fileStream.Dispose();
        }
    }
}
public static void Main(string[] args)
{
    try
    {
        ChromePdfRenderer renderer = new ChromePdfRenderer();
        // Generate PDF from HTML
        var pdf = renderer.RenderHtmlAsPdf("<h1>Hello, World!</h1>");
        pdf.SaveAs("output.pdf");
    }
    catch (IronPdf.Exceptions.IronPdfProductException ex)
    {
        // Handle PDF generation specific exceptions
        Console.WriteLine("Error During IronPDF execution: " + ex.Message);
    }
    catch (Exception ex)
    {
        // Handle general exceptions to avoid any unhandled exception issues
        Console.WriteLine("An unexpected error occurred: " + ex.Message);
    }
    finally
    {
        // Cleanup resources if necessary
        if (fileStream != null)
        {
            fileStream.Close();
            fileStream.Dispose();
        }
    }
}

Output of Finally Block Execution

C# try catch finally (How It Works For Developers): Figure 6

Common Scenarios for Using Try-Catch-Finally with IronPDF

Handling File Not Found and Access Denied Errors

When dealing with file operations in IronPDF, handling exceptions like FileNotFoundException and UnauthorizedAccessException is crucial. These exceptions often arise when files are missing or permissions are restricted. Properly handling these exceptions is essential for maintaining the robustness and reliability of your application, as they often arise when there are issues with file paths, availability, or access permissions.

using IronPdf;
using System.IO;
using IronPdf.Exceptions;
try
{
    // Generate PDF from HTML
    ChromePdfRenderer renderer = new ChromePdfRenderer();
    var pdf = renderer.RenderRtfFileAsPdf(filePath);
    pdf.SaveAs("output.pdf");
}
// The following catch blocks each handle a different exception type
catch (IronPdf.Exceptions.IronPdfProductException ex)
{
    // Handle PDF generation specific exceptions
    Console.WriteLine("Error During IronPDF execution: " + ex.Message);
}
// Handling the IO exception with retry attempts
catch (IOException ex)
        {
        int retries = 5;
            int delay = 1000; // Delay in milliseconds
            Console.WriteLine("IO Exception: " + ex.Message);
            retries--;
            if (retries > 0)
            {
                Console.WriteLine("File is in use. Retrying in " + delay + "ms...");
                System.Threading.Thread.Sleep(delay);
            }
            else
            {
                Console.WriteLine("Failed to access the file after multiple attempts.");
            }
        }
catch (Exception ex)
{
    // Handle general exceptions
    Console.WriteLine("An unexpected error occurred: " + ex.Message);
}
finally
{
    // Delete the temporary file
    if (File.Exists("temp.txt"))
    {
        File.Delete("temp.txt");
        Console.WriteLine("Cleanup Complete!");
    }
}
using IronPdf;
using System.IO;
using IronPdf.Exceptions;
try
{
    // Generate PDF from HTML
    ChromePdfRenderer renderer = new ChromePdfRenderer();
    var pdf = renderer.RenderRtfFileAsPdf(filePath);
    pdf.SaveAs("output.pdf");
}
// The following catch blocks each handle a different exception type
catch (IronPdf.Exceptions.IronPdfProductException ex)
{
    // Handle PDF generation specific exceptions
    Console.WriteLine("Error During IronPDF execution: " + ex.Message);
}
// Handling the IO exception with retry attempts
catch (IOException ex)
        {
        int retries = 5;
            int delay = 1000; // Delay in milliseconds
            Console.WriteLine("IO Exception: " + ex.Message);
            retries--;
            if (retries > 0)
            {
                Console.WriteLine("File is in use. Retrying in " + delay + "ms...");
                System.Threading.Thread.Sleep(delay);
            }
            else
            {
                Console.WriteLine("Failed to access the file after multiple attempts.");
            }
        }
catch (Exception ex)
{
    // Handle general exceptions
    Console.WriteLine("An unexpected error occurred: " + ex.Message);
}
finally
{
    // Delete the temporary file
    if (File.Exists("temp.txt"))
    {
        File.Delete("temp.txt");
        Console.WriteLine("Cleanup Complete!");
    }
}

Example Output: FileNotFound

C# try catch finally (How It Works For Developers): Figure 7

Example Output: IOException

C# try catch finally (How It Works For Developers): Figure 8

Example Output: Unexpected error with IronPdfNativeException

C# try catch finally (How It Works For Developers): Figure 9

Catching and Logging PDF Processing Errors

Logging errors during PDF processing is essential for debugging and monitoring. It allows you to capture detailed information about issues that occur, which can be invaluable for diagnosing problems and improving the reliability of your application.

using IronPdf;
using IronPdf.Logging;
IronPdf.Logging.Logger.LogFilePath = "Default.log";
IronPdf.Logging.Logger.LoggingMode = IronPdf.Logging.Logger.LoggingModes.All;
try
{
    ChromePdfRenderer renderer = new ChromePdfRenderer();
    var pdf = renderer.RenderHtmlFileAsPdf("report.html");
    pdf.SaveAs("output.pdf");
}
catch (Exception ex)
{
    // Log the exception 
    IronSoftware.Logger.Log("PDF processing failed: " + ex.Message);
}
finally
{
    Console.WriteLine("PDF processing attempt finished.");
}
using IronPdf;
using IronPdf.Logging;
IronPdf.Logging.Logger.LogFilePath = "Default.log";
IronPdf.Logging.Logger.LoggingMode = IronPdf.Logging.Logger.LoggingModes.All;
try
{
    ChromePdfRenderer renderer = new ChromePdfRenderer();
    var pdf = renderer.RenderHtmlFileAsPdf("report.html");
    pdf.SaveAs("output.pdf");
}
catch (Exception ex)
{
    // Log the exception 
    IronSoftware.Logger.Log("PDF processing failed: " + ex.Message);
}
finally
{
    Console.WriteLine("PDF processing attempt finished.");
}

Console Output

C# try catch finally (How It Works For Developers): Figure 10

Log Output

C# try catch finally (How It Works For Developers): Figure 11

Ensuring Cleanup and Consistency After Errors

The finally block helps maintain application state consistency by ensuring that all cleanup operations are performed even after an error occurs. Adding a rollback mechanism in the finally block ensures that if an error occurs during the PDF generation process, any changes made during the operation are reverted, maintaining data consistency. This is particularly useful in scenarios where you need to undo actions or clean up changes made during the process.

using IronPdf;
using System.IO;
using System;
using IronPdf.Exceptions;
string tempFilePath = "temp.txt";
bool pdfGenerated = false; // Flag to track if PDF generation was successful
string backupPdfPath = "backup.pdf";
try
{
    File.WriteAllText(tempFilePath, "Temporary content for processing.");
    ChromePdfRenderer renderer = new ChromePdfRenderer();
    var pdf = renderer.RenderHtmlFileAsPdf("report.html");
    pdf.SaveAs("output.pdf");
}
catch (IronPdf.Exceptions.IronPdfProductException ex)
{
    Console.WriteLine("IronPDF error: " + ex.Message);
}
catch (IOException ex)
{
    Console.WriteLine("IO Exception: " + ex.Message);
}
catch (Exception ex)
{
    Console.WriteLine("An unexpected error occurred: " + ex.Message);
}
finally
{
    Console.WriteLine("PDF processing attempt finished.");
    // Delete the temporary file if it exists
    if (File.Exists(tempFilePath))
    {
        File.Delete(tempFilePath);
        Console.WriteLine("Temporary file deleted.");
    }
    // Rollback operations if PDF generation was not successful
    if (!pdfGenerated)
    {
        if (File.Exists(backupPdfPath))
        {
            File.Delete(backupPdfPath);
            Console.WriteLine("Rolled back: Backup PDF deleted.");
        }
    }
    else
    {
        // Ensure the backup PDF is deleted after a successful save
        if (File.Exists(backupPdfPath))
        {
            File.Delete(backupPdfPath); // Remove backup after successful save
            Console.WriteLine("Backup PDF removed after successful save.");
        }
    }
}
using IronPdf;
using System.IO;
using System;
using IronPdf.Exceptions;
string tempFilePath = "temp.txt";
bool pdfGenerated = false; // Flag to track if PDF generation was successful
string backupPdfPath = "backup.pdf";
try
{
    File.WriteAllText(tempFilePath, "Temporary content for processing.");
    ChromePdfRenderer renderer = new ChromePdfRenderer();
    var pdf = renderer.RenderHtmlFileAsPdf("report.html");
    pdf.SaveAs("output.pdf");
}
catch (IronPdf.Exceptions.IronPdfProductException ex)
{
    Console.WriteLine("IronPDF error: " + ex.Message);
}
catch (IOException ex)
{
    Console.WriteLine("IO Exception: " + ex.Message);
}
catch (Exception ex)
{
    Console.WriteLine("An unexpected error occurred: " + ex.Message);
}
finally
{
    Console.WriteLine("PDF processing attempt finished.");
    // Delete the temporary file if it exists
    if (File.Exists(tempFilePath))
    {
        File.Delete(tempFilePath);
        Console.WriteLine("Temporary file deleted.");
    }
    // Rollback operations if PDF generation was not successful
    if (!pdfGenerated)
    {
        if (File.Exists(backupPdfPath))
        {
            File.Delete(backupPdfPath);
            Console.WriteLine("Rolled back: Backup PDF deleted.");
        }
    }
    else
    {
        // Ensure the backup PDF is deleted after a successful save
        if (File.Exists(backupPdfPath))
        {
            File.Delete(backupPdfPath); // Remove backup after successful save
            Console.WriteLine("Backup PDF removed after successful save.");
        }
    }
}

Breakdown of Rollback Logic

  1. Backup Creation:

    • The PDF is initially saved to a backup location (backupPdfPath).

  2. Successful Operation:

    • If the PDF generation is successful (pdfGenerated = true), the backup PDF is moved to the final output location.

  3. Rollback on Failure:

    • If an exception occurs and pdfGenerated remains false, the backup PDF is deleted in the finally block to undo any partial changes.

  4. Cleanup:

    • Regardless of success or failure, the temporary file is deleted in the finally block to ensure no leftover files.

By implementing this rollback mechanism, you ensure that the file system remains in a consistent state, even if an error occurs during the PDF generation process.

Output

C# try catch finally (How It Works For Developers): Figure 12

Benefits of Using IronPDF for Robust Error Handling

Simple and Intuitive API for Exception Handling

IronPDF's API is designed to simplify error handling, making it easier to manage exceptions during complex PDF operations. Compared to other PDF libraries, IronPDF offers a more straightforward approach to exception handling and resource management. Its ability to define specific exception types, such as IronPdfProductException, IronPdfNativeException, and IronPdfUnsupportedException, makes it easier to avoid any unexpected errors or application crashes when you are generating or working with PDF files with IronPDF.

Additionally, the exceptions thrown by IronPDF come with detailed error messages that provide insights into what went wrong. This clarity helps in diagnosing issues more efficiently. For example, IronPdfNativeException might indicate issues with native components, while IronPdfUnsupportedException highlights unsupported features or formats.

Comprehensive Support and Documentation

IronPDF provides detailed documentation and support resources that help developers understand and implement effective error handling practices. This comprehensive support is valuable for troubleshooting and optimizing PDF operations in .NET projects.

IronPDF offers:

  • Comprehensive Documentation: Extensive and user-friendly documentation covering all features.
  • 24/5 Support: Active engineer support is available.
  • Video Tutorials: Step-by-step video guides are available on YouTube.
  • Community Forum: Engaged community for additional support.
  • PDF API reference: Offers API references so you can get the most out of what our tools have to offer.

For more information, check out IronPDF's extensive documentation.

Licensing

If you want to try IronPDF out for yourself and explore its wide range of features, you can easily do so thanks to its free trial period. With its quick and easy installation, you will be able to have IronPDF up and running in your PDF projects in no time. If you want to continue using it and taking advantage of its powerful features to level up your PDF game, licenses start from just $749.

C# try catch finally (How It Works For Developers): Figure 13

Conclusion

Effective error handling using C# try-catch-finally blocks is essential for building robust applications, especially when working with libraries like IronPDF. By understanding and implementing these error handling mechanisms, you can ensure that your PDF generation and manipulation processes are reliable and resilient to unexpected issues.

IronPDF, with its comprehensive and intuitive API, simplifies this process. By offering specific exception types such as IronPdfProductException, IronPdfNativeException, and IronPdfUnsupportedException, IronPDF allows developers to target and manage errors more precisely. This specificity, combined with detailed error messages, helps streamline the debugging process and enhances the overall robustness of your application.

By leveraging IronPDF’s capabilities and following best practices for error handling and resource management, you can ensure that your PDF operations are both reliable and resilient, leading to a more stable and efficient application.

Jordi Bardia
Jordi Bardia
  Chat with engineering team now
Software Engineer
Jordi is most proficient in Python, C# and C++, when he isn’t leveraging his skills at Iron Software; he’s game programming. Sharing responsibilities for product testing, product development and research, Jordi adds immense value to continual product improvement. The varied experience keeps him challenged and engaged, and he says it’s one of his favorite aspects of working with Iron Software. Jordi grew up in Miami, Florida and studied Computer Science and Statistics at University of Florida.
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