How to Batch Convert Excel Files to PDF in .NET

This article demonstrates how to batch convert multiple Excel files to PDF using the Aspose.Cells LowCode PDF Converter in .NET applications. The PDF Converter provides a streamlined approach to document conversion without requiring extensive coding or deep knowledge of Excel internal structures - perfect for business analysts and report developers who need to automate their reporting workflows.

Real-World Problem

In enterprise environments, reporting teams often need to convert dozens or even hundreds of Excel workbooks to PDF format on a regular basis. Doing this manually is time-consuming, error-prone, and diverts valuable resources from more important analytical tasks. Additionally, ensuring consistent formatting and layout across all reports is challenging when converting files individually.

Solution Overview

Using Aspose.Cells LowCode PDF Converter, we can solve this challenge efficiently with minimal code. This solution is ideal for business analysts and report developers who need to streamline their reporting processes, ensure consistency across documents, and free up time for more valuable work. Our approach will focus on creating a robust batch processing system that can handle large volumes of Excel files with custom conversion settings.

Prerequisites

Before implementing the solution, ensure you have:

Visual Studio 2019 or later
.NET 6.0 or later (compatible with .NET Framework 4.6.2+)
Aspose.Cells for .NET package installed via NuGet
Basic understanding of C# programming

PM> Install-Package Aspose.Cells

Step-by-Step Implementation

Step 1: Install and Configure Aspose.Cells

Add the Aspose.Cells package to your project and include the necessary namespaces:

using Aspose.Cells;
using Aspose.Cells.LowCode;
using System;
using System.IO;
using System.Collections.Generic;
using System.Threading.Tasks;

Step 2: Create a Directory Structure for Batch Processing

Set up a directory structure to organize your input Excel files and output PDF files:

// Create directories if they don't exist
string inputDirectory = @"C:\Reports\ExcelFiles";
string outputDirectory = @"C:\Reports\PDFOutput";
string logDirectory = @"C:\Reports\Logs";

Directory.CreateDirectory(inputDirectory);
Directory.CreateDirectory(outputDirectory);
Directory.CreateDirectory(logDirectory);

Step 3: Implement File Discovery Logic

Create a method to discover all Excel files that need to be converted:

private List<string> GetExcelFilesToProcess(string directoryPath, string searchPattern = "*.xlsx")
{
    List<string> excelFiles = new List<string>();
    
    try
    {
        // Get all Excel files (.xlsx) in the directory
        string[] files = Directory.GetFiles(directoryPath, searchPattern);
        excelFiles.AddRange(files);
        
        // Optionally, you can also search for .xls files
        string[] oldFormatFiles = Directory.GetFiles(directoryPath, "*.xls");
        excelFiles.AddRange(oldFormatFiles);
        
        Console.WriteLine($"Found {excelFiles.Count} Excel files to process.");
    }
    catch (Exception ex)
    {
        Console.WriteLine($"Error searching for Excel files: {ex.Message}");
    }
    
    return excelFiles;
}

Step 4: Configure the PDF Converter Options

Create a method to set up the PDF conversion options for consistent output:

private LowCodePdfSaveOptions ConfigurePdfOptions(bool onePagePerSheet = true, 
                                                 bool includeHiddenSheets = false,
                                                 bool printComments = false)
{
    // Create PDF save options
    PdfSaveOptions pdfOpts = new PdfSaveOptions();
    
    // Set whether each worksheet should be rendered as a separate page
    pdfOpts.OnePagePerSheet = onePagePerSheet;
    
    // Option to include hidden worksheets in the output
    pdfOpts.AllColumnsInOnePagePerSheet = true;
    
    // Configure additional PDF options
    pdfOpts.Compliance = PdfCompliance.PdfA1b; // For archival quality
    pdfOpts.PrintingPageType = PrintingPageType.ActualSize;
    
    // Configure comment display options
    pdfOpts.PrintComments = printComments ? PrintCommentsType.PrintInPlace : PrintCommentsType.PrintNoComments;
    
    // Create low code PDF save options
    LowCodePdfSaveOptions lcsopts = new LowCodePdfSaveOptions();
    lcsopts.PdfOptions = pdfOpts;
    
    return lcsopts;
}

Step 5: Implement Single File Conversion Logic

Create a method to convert a single Excel file to PDF:

private bool ConvertExcelToPdf(string inputFilePath, string outputFilePath, LowCodePdfSaveOptions pdfOptions)
{
    try
    {
        // Create load options
        LowCodeLoadOptions loadOptions = new LowCodeLoadOptions();
        loadOptions.InputFile = inputFilePath;
        
        // Set output file path
        pdfOptions.OutputFile = outputFilePath;
        
        // Process the conversion
        PdfConverter.Process(loadOptions, pdfOptions);
        
        return true;
    }
    catch (Exception ex)
    {
        Console.WriteLine($"Error converting {Path.GetFileName(inputFilePath)}: {ex.Message}");
        return false;
    }
}

Step 6: Implement Batch Processing Logic

Now create the main method that will process multiple files:

public void BatchConvertExcelToPdf(string inputDirectory, string outputDirectory, string searchPattern = "*.xlsx")
{
    // Get all Excel files
    List<string> excelFiles = GetExcelFilesToProcess(inputDirectory, searchPattern);
    
    // Configure PDF options
    LowCodePdfSaveOptions pdfOptions = ConfigurePdfOptions(true, false, false);
    
    // Track conversion statistics
    int successCount = 0;
    int failureCount = 0;
    
    // Process each file
    foreach (string excelFile in excelFiles)
    {
        string fileName = Path.GetFileNameWithoutExtension(excelFile);
        string outputFilePath = Path.Combine(outputDirectory, $"{fileName}.pdf");
        
        Console.WriteLine($"Converting: {fileName}");
        
        bool success = ConvertExcelToPdf(excelFile, outputFilePath, pdfOptions);
        
        if (success)
        {
            successCount++;
            Console.WriteLine($"Successfully converted: {fileName}");
        }
        else
        {
            failureCount++;
            Console.WriteLine($"Failed to convert: {fileName}");
        }
    }
    
    // Report summary
    Console.WriteLine("\n===== Conversion Summary =====");
    Console.WriteLine($"Total files processed: {excelFiles.Count}");
    Console.WriteLine($"Successfully converted: {successCount}");
    Console.WriteLine($"Failed conversions: {failureCount}");
}

Step 7: Implement Parallel Processing for Better Performance

For large batches, implement parallel processing to speed up conversion:

public void ParallelBatchConvertExcelToPdf(string inputDirectory, string outputDirectory, string searchPattern = "*.xlsx")
{
    // Get all Excel files
    List<string> excelFiles = GetExcelFilesToProcess(inputDirectory, searchPattern);
    
    // Track conversion statistics
    int successCount = 0;
    int failureCount = 0;
    object lockObj = new object();
    
    // Configure PDF options (will be reused for each conversion)
    LowCodePdfSaveOptions pdfOptions = ConfigurePdfOptions(true, false, false);
    
    // Process files in parallel
    Parallel.ForEach(excelFiles, 
        new ParallelOptions { MaxDegreeOfParallelism = Environment.ProcessorCount }, 
        excelFile =>
    {
        string fileName = Path.GetFileNameWithoutExtension(excelFile);
        string outputFilePath = Path.Combine(outputDirectory, $"{fileName}.pdf");
        
        // Each thread needs its own copy of the options
        LowCodePdfSaveOptions threadPdfOptions = ConfigurePdfOptions(true, false, false);
        threadPdfOptions.OutputFile = outputFilePath;
        
        Console.WriteLine($"Converting: {fileName}");
        
        // Create load options
        LowCodeLoadOptions loadOptions = new LowCodeLoadOptions();
        loadOptions.InputFile = excelFile;
        
        try
        {
            // Process the conversion
            PdfConverter.Process(loadOptions, threadPdfOptions);
            
            lock (lockObj)
            {
                successCount++;
                Console.WriteLine($"Successfully converted: {fileName}");
            }
        }
        catch (Exception ex)
        {
            lock (lockObj)
            {
                failureCount++;
                Console.WriteLine($"Failed to convert {fileName}: {ex.Message}");
            }
        }
    });
    
    // Report summary
    Console.WriteLine("\n===== Conversion Summary =====");
    Console.WriteLine($"Total files processed: {excelFiles.Count}");
    Console.WriteLine($"Successfully converted: {successCount}");
    Console.WriteLine($"Failed conversions: {failureCount}");
}

Step 8: Complete Implementation Example

Here’s a complete working example that demonstrates the entire batch conversion process:

using Aspose.Cells;
using Aspose.Cells.LowCode;
using System;
using System.Collections.Generic;
using System.IO;
using System.Threading.Tasks;

namespace ExcelBatchConverter
{
    public class ExcelToPdfBatchConverter
    {
        private readonly string _inputDirectory;
        private readonly string _outputDirectory;
        private readonly string _logDirectory;
        
        public ExcelToPdfBatchConverter(string inputDirectory, string outputDirectory, string logDirectory)
        {
            _inputDirectory = inputDirectory;
            _outputDirectory = outputDirectory;
            _logDirectory = logDirectory;
            
            // Ensure directories exist
            Directory.CreateDirectory(_inputDirectory);
            Directory.CreateDirectory(_outputDirectory);
            Directory.CreateDirectory(_logDirectory);
        }
        
        // Log the conversion activity
        private void LogConversion(string message)
        {
            string logFilePath = Path.Combine(_logDirectory, $"ConversionLog_{DateTime.Now.ToString("yyyyMMdd")}.txt");
            string logEntry = $"[{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")}] {message}";
            
            try
            {
                File.AppendAllText(logFilePath, logEntry + Environment.NewLine);
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Warning: Unable to write to log file: {ex.Message}");
            }
            
            Console.WriteLine(logEntry);
        }
        
        // Get all Excel files to process
        private List<string> GetExcelFilesToProcess(string searchPattern = "*.xlsx")
        {
            List<string> excelFiles = new List<string>();
            
            try
            {
                // Get all Excel files in the directory
                excelFiles.AddRange(Directory.GetFiles(_inputDirectory, "*.xlsx"));
                excelFiles.AddRange(Directory.GetFiles(_inputDirectory, "*.xls"));
                excelFiles.AddRange(Directory.GetFiles(_inputDirectory, "*.xlsm"));
                
                LogConversion($"Found {excelFiles.Count} Excel files to process.");
            }
            catch (Exception ex)
            {
                LogConversion($"Error searching for Excel files: {ex.Message}");
            }
            
            return excelFiles;
        }
        
        // Configure PDF conversion options
        private LowCodePdfSaveOptions ConfigurePdfOptions()
        {
            // Create PDF save options
            PdfSaveOptions pdfOpts = new PdfSaveOptions();
            
            // Set whether each worksheet should be rendered as a separate page
            pdfOpts.OnePagePerSheet = true;
            
            // Set additional PDF options
            pdfOpts.Compliance = PdfCompliance.PdfA1b; // For archival quality
            pdfOpts.AllColumnsInOnePagePerSheet = true;
            
            // Create low code PDF save options
            LowCodePdfSaveOptions lcsopts = new LowCodePdfSaveOptions();
            lcsopts.PdfOptions = pdfOpts;
            
            return lcsopts;
        }
        
        // Process all Excel files in the input directory
        public void ProcessAllFiles(bool useParallelProcessing = true)
        {
            LogConversion("Starting batch conversion process...");
            
            List<string> excelFiles = GetExcelFilesToProcess();
            
            if (excelFiles.Count == 0)
            {
                LogConversion("No Excel files found to process.");
                return;
            }
            
            // Conversion statistics
            int successCount = 0;
            int failureCount = 0;
            
            if (useParallelProcessing)
            {
                // For thread safety with parallel processing
                object lockObj = new object();
                
                // Process files in parallel
                Parallel.ForEach(excelFiles, 
                    new ParallelOptions { MaxDegreeOfParallelism = Environment.ProcessorCount }, 
                    excelFile =>
                {
                    string fileName = Path.GetFileNameWithoutExtension(excelFile);
                    string outputFilePath = Path.Combine(_outputDirectory, $"{fileName}.pdf");
                    
                    try
                    {
                        // Create load options for this file
                        LowCodeLoadOptions loadOptions = new LowCodeLoadOptions();
                        loadOptions.InputFile = excelFile;
                        
                        // Configure PDF options for this file
                        LowCodePdfSaveOptions pdfOptions = ConfigurePdfOptions();
                        pdfOptions.OutputFile = outputFilePath;
                        
                        // Process the conversion
                        PdfConverter.Process(loadOptions, pdfOptions);
                        
                        lock (lockObj)
                        {
                            successCount++;
                            LogConversion($"Successfully converted: {fileName}");
                        }
                    }
                    catch (Exception ex)
                    {
                        lock (lockObj)
                        {
                            failureCount++;
                            LogConversion($"Failed to convert {fileName}: {ex.Message}");
                        }
                    }
                });
            }
            else
            {
                // Process files sequentially
                foreach (string excelFile in excelFiles)
                {
                    string fileName = Path.GetFileNameWithoutExtension(excelFile);
                    string outputFilePath = Path.Combine(_outputDirectory, $"{fileName}.pdf");
                    
                    try
                    {
                        // Create load options for this file
                        LowCodeLoadOptions loadOptions = new LowCodeLoadOptions();
                        loadOptions.InputFile = excelFile;
                        
                        // Configure PDF options for this file
                        LowCodePdfSaveOptions pdfOptions = ConfigurePdfOptions();
                        pdfOptions.OutputFile = outputFilePath;
                        
                        // Process the conversion
                        PdfConverter.Process(loadOptions, pdfOptions);
                        
                        successCount++;
                        LogConversion($"Successfully converted: {fileName}");
                    }
                    catch (Exception ex)
                    {
                        failureCount++;
                        LogConversion($"Failed to convert {fileName}: {ex.Message}");
                    }
                }
            }
            
            // Report summary
            LogConversion("\n===== Conversion Summary =====");
            LogConversion($"Total files processed: {excelFiles.Count}");
            LogConversion($"Successfully converted: {successCount}");
            LogConversion($"Failed conversions: {failureCount}");
            LogConversion("Batch conversion process completed.");
        }
    }
    
    class Program
    {
        static void Main(string[] args)
        {
            // Define directory paths
            string inputDirectory = @"C:\Reports\ExcelFiles";
            string outputDirectory = @"C:\Reports\PDFOutput";
            string logDirectory = @"C:\Reports\Logs";
            
            // Create and run the converter
            ExcelToPdfBatchConverter converter = new ExcelToPdfBatchConverter(
                inputDirectory, outputDirectory, logDirectory);
                
            // Process all files (using parallel processing)
            converter.ProcessAllFiles(true);
            
            Console.WriteLine("Process completed. Press any key to exit.");
            Console.ReadKey();
        }
    }
}

Use Cases and Applications

Enterprise Reporting Systems

In financial reporting systems, month-end or quarter-end cycles often require converting numerous Excel-based reports to PDF format for distribution to stakeholders. This batch conversion solution enables report developers to automate the process, ensuring all reports are converted with consistent settings and formatting, while dramatically reducing manual effort. Reports can be automatically archived in a standardized format, making retrieval and compliance easier.

Departmental Data Processing

Business analysts who collect Excel-based data from multiple departments can use this solution to standardize and archive submissions. By automatically converting received workbooks to PDF, they create a permanent record of data submissions while making the information shareable with stakeholders who don’t have Excel. The batch processing capability means even large departments with hundreds of workbooks can be processed efficiently.

Automated Document Management Workflows

Integration with document management systems becomes seamless when Excel reports are automatically converted to PDF. This solution can be scheduled to run as part of a larger workflow that picks up new Excel files, converts them to PDF, and then routes them to the appropriate document repositories with proper metadata. The consistent formatting and archival-quality PDF output ensures long-term accessibility of business data.

Common Challenges and Solutions

Challenge 1: Handling Excel Files with Password Protection

Solution: Modify the load options to include password handling:

// For password-protected Excel files
LowCodeLoadOptions loadOptions = new LowCodeLoadOptions();
loadOptions.InputFile = excelFile;
loadOptions.Password = "YourPassword"; // Supply the password

// Then proceed with conversion as normal
PdfConverter.Process(loadOptions, pdfOptions);

Challenge 2: Maintaining Excel Formatting in PDF Output

Solution: Ensure the PDF options are properly configured to preserve formatting:

PdfSaveOptions pdfOpts = new PdfSaveOptions();
pdfOpts.OnePagePerSheet = true;
pdfOpts.PrintingPageType = PrintingPageType.ActualSize;
pdfOpts.DefaultFontName = "Arial"; // Specify a fallback font
pdfOpts.Compliance = PdfCompliance.PdfA1b; // For archival quality

Challenge 3: Handling Very Large Excel Files

Solution: For extremely large files, implement memory optimization:

LowCodeLoadOptions loadOptions = new LowCodeLoadOptions();
loadOptions.InputFile = largeExcelFile;
loadOptions.MemorySetting = MemorySetting.MemoryPreference; // Optimize for memory usage

// Consider file-specific optimizations
PdfSaveOptions pdfOpts = new PdfSaveOptions();
pdfOpts.OptimizationType = OptimizationType.MinimumSize;

Performance Considerations

For optimal performance with large batches, use the parallel processing approach with a reasonable MaxDegreeOfParallelism based on your server’s capabilities
Consider processing files in smaller batches when dealing with very large Excel workbooks to avoid memory pressure
Implement a monitoring mechanism to track conversion progress and resource utilization
For production deployments, consider running the conversion process on a dedicated server or during off-peak hours

Best Practices

Pre-validate Excel files before batch processing to identify potential issues
Implement robust error handling to ensure the process doesn’t stop if one file fails
Create detailed logs of the conversion process for troubleshooting and auditing
Organize output PDFs in a structured folder hierarchy for easier management
Set up a monitoring system that alerts administrators of conversion failures
Test with various Excel file types (XLSX, XLS, XLSM) to ensure compatibility

Advanced Scenarios

For more complex requirements, consider these advanced implementations:

Scenario 1: Custom PDF Naming Based on Excel Cell Content

You can extract specific cell values to use in the PDF filename:

// Advanced naming based on cell content
private string GetCustomPdfName(string excelFilePath)
{
    try
    {
        // Load the workbook
        Workbook workbook = new Workbook(excelFilePath);
        
        // Get report date from cell A1
        string reportDate = workbook.Worksheets[0].Cells["A1"].StringValue;
        
        // Get report type from cell B1
        string reportType = workbook.Worksheets[0].Cells["B1"].StringValue;
        
        // Create a custom name
        string customName = $"{reportType}_{reportDate}";
        
        // Sanitize the filename
        foreach (char invalidChar in Path.GetInvalidFileNameChars())
        {
            customName = customName.Replace(invalidChar, '_');
        }
        
        return customName + ".pdf";
    }
    catch
    {
        // Fallback to default naming if extraction fails
        return Path.GetFileNameWithoutExtension(excelFilePath) + ".pdf";
    }
}

Scenario 2: Selective Sheet Conversion

Convert only specific sheets from each Excel file:

// Configure PDF options to convert only specific sheets
private LowCodePdfSaveOptions ConfigureSelectiveSheetsOptions(string[] sheetNames)
{
    PdfSaveOptions pdfOpts = new PdfSaveOptions();
    pdfOpts.OnePagePerSheet = true;
    
    // Create a worksheet name collection for selective conversion
    WorksheetCollection worksheets = new WorksheetCollection();
    foreach (string sheetName in sheetNames)
    {
        worksheets.Add(sheetName);
    }
    
    // Set sheet selection
    SheetOptions sheetOptions = new SheetOptions();
    sheetOptions.SheetNames = worksheets;
    pdfOpts.SheetOptions = sheetOptions;
    
    // Create low code PDF save options
    LowCodePdfSaveOptions lcsopts = new LowCodePdfSaveOptions();
    lcsopts.PdfOptions = pdfOpts;
    
    return lcsopts;
}

Conclusion

By implementing Aspose.Cells LowCode PDF Converter for batch processing, business analysts and report developers can dramatically reduce the time spent on manual Excel to PDF conversions. This approach significantly improves productivity and ensures consistency across all generated PDFs while maintaining the quality and formatting of the original Excel files. The solution is scalable from small departmental use to enterprise-wide reporting systems, with options for customization to meet specific business requirements.

For more information and additional examples, refer to the Aspose.Cells.LowCode API Reference .