# Dealing with FileNotFoundException - Could not Load File or Assembly System.IO.Hashing

## Environment

| Version                              | Product          | Author                                                                          |
| ------------------------------------ | ---------------- | ------------------------------------------------------------------------------- |
| 2026.1.304                           | RadPdfProcessing | [Desislava Yordanova](https://www.telerik.com/blogs/author/desislava-yordanova) |
| .NET 8 (or newer) Target OS: Windows | Target Framework | -                                                                               |

## Description

When exporting a PDF document using the [PdfFormatProvider](https://www.telerik.com/document-processing-libraries/documentation/libraries/radpdfprocessing/formats-and-conversion/pdf/pdfformatprovider/pdfformatprovider), the following error occurs:
`System.IO.FileNotFoundException: 'Could not load file or assembly 'System.IO.Hashing'`.

## Solution

The `Telerik.Windows.Documents.Fixed` NuGet package has a dependency on `System.IO.Hashing` introduced in version 2026.1.304.

If your project throws the exception at runtime, install the [System.IO.Hashing](https://www.nuget.org/packages/System.IO.Hashing/) NuGet package manually.

## See Also

* [PdfProcessing Overview](https://www.telerik.com/document-processing-libraries/documentation/libraries/radpdfprocessing/overview)