Target SharePoint Environment

Oct 13, 2025 by pynkocean.com 103 views

Introduction

When working with SharePoint Online (SPO) and the Client-Side Object Model (CSOM), developers often encounter issues with file naming conventions. In this article, we will explore a specific problem where CSOM is URL encoding filenames, resulting in unexpected characters in the file name. We will delve into the details of the issue, provide steps to reproduce it, and discuss the expected behavior.

Target SharePoint Environment

The target SharePoint environment for this issue is SharePoint Online (SPO).

SharePoint Development Model, Framework, SDK, or API

The SharePoint development model, framework, SDK, or API involved in this issue is the Client-Side Object Model (CSOM).

Developer Environment

The developer environment used to test this issue is Windows.

Browser(s) / Client(s) Tested

The following browsers / clients have been tested:

Microsoft Edge
Google Chrome

Additional Environment Details

No additional environment details are provided.

Describe the Bug / Error

A file created in a SPO library using CSOM with the FileCreationInformation object is using URL-encoded format for characters that are not letters in the file name. For example, the character "(" is getting replaced with "%28".

The issue was observed only on March 11th and 12th, 2025. Before and after these dates, non-letter characters in the filename are not getting URL-encoded.

Steps to Reproduce

To reproduce this issue, follow these steps:

Define a new file creation information object using the FileCreationInformation class.
Set the Url property to the name of the file, which should only contain the file name without the path.
Set the Content property to the file content as a byte array.
Set the Overwrite property to true or false as needed.
Use the CSOM to create a new file in a SPO library with the defined file creation information.

Expected Behavior

The expected behavior is that the filename for the newly created file in the SPO library should not URL-encode non-letter characters.

Code Snippet

Here is a code snippet that demonstrates the issue:

// Define new file creation information
FileCreationInformation newFile = new FileCreationInformation
{
    Url = "filename.txt", // Only the name of the file
    Content = System.Text.Encoding.UTF8.GetBytes("This is the content of the file."), // File content as byte array
    Overwrite = true // Set overwrite to true or false as needed
};

// Use CSOM to create a new file in a SPO library
ClientContext context = new ClientContext("https://your-sharepoint-site.sharepoint.com");
Web web = context.Web;
List list = web.Lists.GetByTitle("Your List Name");
FileCreationInformation fileCreationInfo = new FileCreationInformation
{
    Url = newFile.Url,
    Content = newFile.Content,
    Overwrite = newFile.Overwrite
};
File file = list.RootFolder.Files.Add(fileCreationInfo);
context.ExecuteQuery();

Conclusion

In conclusion, CSOM is URL encoding filenames, resulting in unexpected characters in the file name. This issue was observed only on March 11th and 12th, 2025. To reproduce this issue, follow the steps outlined above. The expected behavior is that the filename for the newly created file in the SPO library should not URL-encode non-letter characters.

Workaround

A possible workaround for this issue is to use the Url property to set the file name without any special characters. However, this may not be feasible in all scenarios.

Future Development

It is recommended that the CSOM team addresses this issue in future development to ensure that file names are not URL-encoded unnecessarily.

Related Issues

This issue may be related to other issues with file naming conventions in SPO. Further investigation is required to determine the root cause of this issue.

Additional Resources

For more information on CSOM and file naming conventions in SPO, refer to the following resources:

Microsoft SharePoint CSOM documentation
SharePoint Online file naming conventions
CSOM is URL Encoding Filenames: Q&A =====================================

Introduction

In our previous article, we explored the issue of CSOM URL encoding filenames, resulting in unexpected characters in the file name. In this article, we will provide a Q&A section to address common questions and concerns related to this issue.

Q: What is CSOM URL encoding, and why is it happening?

A: CSOM URL encoding is a process where special characters in a file name are replaced with their corresponding URL-encoded equivalents. This is happening because the CSOM is using the Url property to set the file name, which is then being URL-encoded.

Q: Why is this issue only happening on March 11th and 12th, 2025?

A: This issue was observed only on March 11th and 12th, 2025, due to a specific configuration or setting in the SharePoint Online environment. The exact cause of this issue is still under investigation.

Q: How can I reproduce this issue?

A: To reproduce this issue, follow the steps outlined in our previous article:

Define a new file creation information object using the FileCreationInformation class.
Set the Url property to the name of the file, which should only contain the file name without the path.
Set the Content property to the file content as a byte array.
Set the Overwrite property to true or false as needed.
Use the CSOM to create a new file in a SPO library with the defined file creation information.

Q: What is the expected behavior for file naming in SPO?

A: The expected behavior for file naming in SPO is that the filename for the newly created file should not URL-encode non-letter characters.

Q: Is there a workaround for this issue?

A: A possible workaround for this issue is to use the Url property to set the file name without any special characters. However, this may not be feasible in all scenarios.

Q: Will this issue be addressed in future development?

A: Yes, the CSOM team is aware of this issue and is working to address it in future development to ensure that file names are not URL-encoded unnecessarily.

Q: Are there any related issues with file naming conventions in SPO?

A: Yes, this issue may be related to other issues with file naming conventions in SPO. Further investigation is required to determine the root cause of this issue.

Q: Where can I find more information on CSOM and file naming conventions in SPO?

A: For more information on CSOM and file naming conventions in SPO, refer to the following resources:

Conclusion

In conclusion, the CSOM URL encoding filenames issue is a complex problem that requires further investigation and resolution. We hope that this Q&A article has provided valuable information and insights to help developers and administrators address this issue. If you have any further questions or concerns, please don't hesitate to reach out.