使用C#借助Microsoft.SharePoint.Client从SharePoint批量下载Excel文件

Got it, here's a complete implementation using the SharePoint Client Object Model (via the Microsoft.SharePoint.Client DLL) to download all Excel files from a SharePoint site to a specified local folder. I’ll walk you through the code and break down the key bits so you can adapt it to your needs.

Prerequisites #

• Install the required NuGet package:
  • For SharePoint Online: Install Microsoft.SharePointOnline.CSOM (this includes the core Microsoft.SharePoint.Client DLLs)
  • For On-premises SharePoint: Install Microsoft.SharePoint.Client and Microsoft.SharePoint.Client.Runtime
• Ensure you have read permissions to the target SharePoint site and all its document libraries/folders
• The local target folder can be auto-created by the code (we’ve included that logic)

Full C# Code Example #

using System;
using System.IO;
using System.Security;
using Microsoft.SharePoint.Client;

class SharePointExcelDownloader
{
    static void Main(string[] args)
    {
        // Update these values to match your environment
        string siteUrl = "https://your-sharepoint-site-url";
        string username = "your-username@domain.com"; // SPO: work/school account; On-prem: domain\username
        string password = "your-password";
        string localDownloadFolder = @"C:\Your\Local\Download\Folder";

        // Create local folder if it doesn't exist
        if (!Directory.Exists(localDownloadFolder))
        {
            Directory.CreateDirectory(localDownloadFolder);
            Console.WriteLine($"Created local folder: {localDownloadFolder}");
        }

        // Initialize SharePoint Client Context
        using (ClientContext context = new ClientContext(siteUrl))
        {
            // Authenticate - switch between SPO and On-prem as needed
            context.Credentials = new SharePointOnlineCredentials(username, ConvertToSecureString(password));
            // For On-prem: context.Credentials = new System.Net.NetworkCredential(username, password, "your-domain");

            try
            {
                // Fetch all document libraries in the site
                Web web = context.Web;
                context.Load(web.Lists, lists => lists.Include(list => list.Title, list => list.RootFolder)
                                                     .Where(list => list.BaseType == BaseType.DocumentLibrary));
                context.ExecuteQuery();

                foreach (List library in web.Lists)
                {
                    Console.WriteLine($"\nProcessing library: {library.Title}");
                    // Recursively scan all folders and files in the library
                    ProcessFolder(context, library.RootFolder, localDownloadFolder);
                }

                Console.WriteLine("\n✅ All Excel files downloaded successfully!");
            }
            catch (Exception ex)
            {
                Console.WriteLine($"\n❌ Error occurred: {ex.Message}");
            }
        }
    }

    private static void ProcessFolder(ClientContext context, Folder folder, string localRootFolder)
    {
        // Load folder contents (subfolders and files)
        context.Load(folder, f => f.Folders, f => f.Files);
        context.ExecuteQuery();

        // Create matching local folder structure
        string localFolderPath = Path.Combine(localRootFolder, folder.ServerRelativeUrl.TrimStart('/').Replace('/', '\\'));
        if (!Directory.Exists(localFolderPath))
        {
            Directory.CreateDirectory(localFolderPath);
        }

        // Download Excel files in current folder
        foreach (File file in folder.Files)
        {
            string fileExt = Path.GetExtension(file.Name).ToLower();
            // Check for common Excel file types
            if (fileExt is ".xlsx" or ".xls" or ".xlsm" or ".xlsb")
            {
                Console.WriteLine($"Downloading: {file.Name}");
                DownloadFile(context, file, localFolderPath);
            }
        }

        // Recursively process subfolders
        foreach (Folder subFolder in folder.Folders)
        {
            ProcessFolder(context, subFolder, localRootFolder);
        }
    }

    private static void DownloadFile(ClientContext context, File file, string localFolderPath)
    {
        // Fetch file content from SharePoint
        FileInformation fileInfo = File.OpenBinaryDirect(context, file.ServerRelativeUrl);

        // Save to local disk
        string localFilePath = Path.Combine(localFolderPath, file.Name);
        using (FileStream fs = new FileStream(localFilePath, FileMode.Create))
        {
            fileInfo.Stream.CopyTo(fs);
        }
    }

    private static SecureString ConvertToSecureString(string password)
    {
        SecureString secureString = new SecureString();
        foreach (char c in password)
        {
            secureString.AppendChar(c);
        }
        return secureString;
    }
}

Key Notes & Explanations #

• Authentication: We’ve included both SharePoint Online and on-prem authentication options—just comment/uncomment the relevant line. For production, avoid hardcoding passwords; use a secure credential store like Azure Key Vault instead.
• Recursive Scanning: The ProcessFolder method digs through all subfolders in each document library, so you won’t miss any nested Excel files.
• File Filtering: We check for the most common Excel extensions, but you can add/remove extensions (like .xltx for templates) as needed.
• Local Structure: The code replicates the SharePoint folder hierarchy locally, so you’ll have the same organization as the original site.
• Error Handling: Basic exception catching is included—you can expand this to log errors to a file or handle specific issues like permission denials.

内容的提问来源于stack exchange，提问作者Jithin Gangadharan