Retrieve Files And Folders Recursively From A Sharepoint Document Library

What is Recursive File Retrieval?

Recursive file retrieval refers to the process of accessing and downloading all files and subfolders within a SharePoint document library or site collection in a programmatic, automated fashion. This allows for batch processing of potentially thousands of files for backup, migration, indexing, or further processing with other systems.

Rather than manually browsing or searching for content in SharePoint, recursive methods traverse the folder hierarchy to find and act on every file. Some key capabilities this enables:

Downloading entire document libraries for backup or offline use
Migrating all files to another repository or file share
Indexing or extracting metadata from documents collections
Integrating document management processes with other systems

Automated recursive processing is essential for large libraries with fluctuating content sets and unknown folder structures. Manual per-folder downloads do not scale and miss newly added material.

Table of Contents

Why Retrieve Files Recursively?

There are several common scenarios which require the ability to batch retrieve documents from SharePoint sites:

Content Migration: When transitioning enterprise content to a new document repository, all files must be extracted – recursion guarantees full coverage.

Offline Sync: Syncing team sites to local drives benefits from downloading updates to the entire site versus manual folder selection.

Search Indexing: Before indexing in external engines, documents must be recursively crawled from the original SharePoint environment.

Processing Pipelines: ETL, file conversion, metadata extraction, and other automated document processing require batch importing the full corpus.

Additional use cases:

Creating localized copies of resource files
Emailing team site contents as attachments
Analyzing storage consumption across all sites
Archival of project files to tape storage

Any scenario involving uncertainty around the underlying folder structure and file population needs recursion to guarantee full coverage.

Methods for Recursive File Retrieval

SharePoint provides several interfaces which can access content recursively:

SharePoint REST API

The SharePoint REST API exposes common CRUD operations for sites, lists, libraries, list items, documents, and more. This includes recursion parameters when retrieving folders and files.

Key endpoints supporting recursion:

/_api/web/GetFolderByServerRelativePath
/_api/web/GetFileByServerRelativePath
/_api/web/GetFolderByServerRelativeUrl
/_api/web/GetFileByServerRelativeUrl

By passing in the parent folder then iterating child items, an entire tree can be processed.

PowerShell and Get-PnPFile Cmdlet

SharePoint PowerShell includes purpose-built commands for accessing documents. In particular Get-PnPFile downloads files recursively with a single parameter:

“`
Get-PnPFile -SiteRelativeUrl /documents/ -Path projects -Recurse
“`

This simplicity has made PowerShell a popular option for automation.

CSOM – Client Side Object Model

CSOM provides .NET API access across SharePoint environments. Includes Folder.Files and Folder.SubFolders properties for traversal:

“`csharp
SharePointFolder rootFolder = context.Web.GetFolder(“projects”);
ProcessFolder(rootFolder);

void ProcessFolder(SharePointFolder folder)
{
foreach (File file in folder.Files) {
// file processing
}

foreach (SharePointFolder subFolder in folder.SubFolders) {
ProcessFolder(subFolder);
}
}
“`

CSOM remains relevant despite growth of REST API and PowerShell.

Sample Code for Recursive File Download

Example PowerShell script to download all files under a document library:

“`powershell
#Parameters
$SiteUrl = “https://tenant.sharepoint.com/sites/team”
$LibraryName =”Shared Documents”
$OutputPath = “C:\users\temp\downloads”

#Connect to PnP Online
Connect-PnPOnline -Url $SiteUrl -UseWebLogin

#Ensure output folder exists
New-Item -ItemType Directory -Force -Path $OutputPath

#Retrieve all files recursively and save to local path
Get-PnPFile -SiteRelativeUrl “/sites/team/$LibraryName” -Path * -Recurse | ForEach-Object {
$OutputFile = Join-Path $OutputPath $_.ServerRelativeUrl.Substring($LibraryName.Length)
$Folder = Split-Path $OutputFile -Parent
New-Item -ItemType Directory -Force -Path $Folder
Get-PnPFile -Url $_.ServerRelativeUrl -Path $OutputFile -AsFile
}

Write-Host “Completed recursive file download from SharePoint Online library ‘$LibraryName'”
“`

C# example using CSOM to traverse folders and download files:

“`csharp
static void ProcessFolder(ClientContext ctx, SharePointFolder folder, string localPath)
{
ctx.Load(folder.Folders);
ctx.Load(folder.Files);
ctx.ExecuteQuery();

// Create matching local folder
string newFolder = Path.Combine(localPath, folder.Name);
Directory.CreateDirectory(newFolder);

// Write out each file
foreach (ClientObject file in folder.Files) {
ClientResult data = file.OpenBinaryStream();
ctx.ExecuteQuery();
// Save stream to new file
using (FileStream fileStream = File.Create(Path.Combine(newFolder, file.Name))) {
CopyStream(data.Value, fileStream);
}
}

// Recurse through subfolders
foreach (SharePointFolder subFolder in folder.Folders) {
ProcessFolder(ctx, subFolder, newFolder);
}
}
“`

Key takeaways:

Rely on native SharePoint commands for recursion
Iterate through folder structure
Save content to local files/streams as needed

Considerations and Best Practices

When retrieving files recursively, be aware of the following:

Performance: Fetching thousands of files is resource intensive – use batching and throttling to avoid overload. Balance volume and speed.

Security: Credentials used must have read access widely through site collection to access all documents.

Very Large Libraries: At extreme scales beyond 100,000+ files, adjust approach to use search indexing, backup API, or leverage flat metadata.

Additional best practices:

Monitor scripts for errors and throttle if necessary.
If downloading, choose a path with ample disk space.
Handle file locks, timeouts, and retries.

Tuning batch sizes, polling intervals, parallel threads and other parameters can optimize recursive jobs for efficiency and stability.

Additional Tips for Working with SharePoint Files

Other considerations when automating SharePoint file operations:

Metadata: Extract metadata columns through CSOM for use in processing – don’t just copy files blindly.

Versioning: Retrieve specific file versions where applicable via API parameters – don’t just grab the latest by default.

Additional capabilities:

Update metadata in bulk by writing back to SharePoint.
Compare file differences across versions.
Trigger workflows and events remotely via API after updates.

For richest integration with SharePoint content leverage more than just raw files – use accompanying metadata and services as well.

Summary