Attach files to List/Library using Managed Client Object Model

Upload File in Library

The following code snippet shows how to upload file in document library:

public void UploadFileInLibrary(string siteUrl, string webName, string libraryName, string subfolderPath, string fileName)
{
    using (ClientContext clientContext = new ClientContext(siteUrl))
    {

        string uploadLocation = Path.GetFileName(fileName);
        if (!string.IsNullOrEmpty(subfolderPath))
        {
            uploadLocation = string.Format("{0}/{1}", subfolderPath, uploadLocation);
        }
        uploadLocation = string.Format("/{0}/{1}/{2}", webName, libraryName, uploadLocation);
        var list = clientContext.Web.Lists.GetByTitle(libraryName);
        var fileCreationInformation = new FileCreationInformation();
        fileCreationInformation.Content = System.IO.File.ReadAllBytes(fileName);
        fileCreationInformation.Overwrite = true;
        fileCreationInformation.Url = uploadLocation;
        list.RootFolder.Files.Add(fileCreationInformation);
        clientContext.ExecuteQuery();
    }
}

Download File From Library

The following code snippets shows how to download file from library:

public void DownloadFileFromLibrary(string siteUrl, string webName, string libraryName, string subfolderPath, string fileName, string downloadPath)
{
    using (ClientContext clientContext = new ClientContext(siteUrl))
    {
        string filePath = string.Empty;
        if (!string.IsNullOrEmpty(subfolderPath))
        {
            filePath = string.Format("/{0}/{1}/{2}/{3}", webName, libraryName, subfolderPath, fileName);
        }
        else
        {
            filePath = string.Format("/{0}/{1}/{2}", webName, subfolderPath, fileName);
        }

        var fileInformation = File.OpenBinaryDirect(clientContext, filePath);
        var stream = fileInformation.Stream;
        IList<byte> content = new List<byte>();
        int b;
        while ((b = fileInformation.Stream.ReadByte()) != -1)
        {
            content.Add((byte)b);
        }
        var downloadFileName = Path.Combine(downloadPath, fileName);
        System.IO.File.WriteAllBytes(downloadFileName, content.ToArray());
        fileInformation.Stream.Close();
    }
}

Delete File From Library

The following code snippet shows how to delete file from library:

public void DeleteFileFormLibrary(string siteUrl, string webName, string listName, string subfolder, string attachmentFileName)
{
    using (ClientContext clientContext = new ClientContext(siteUrl))
    {
        string attachmentPath = string.Empty;
        if (string.IsNullOrEmpty(subfolder))
        {
            attachmentPath = string.Format("/{0}/{1}/{2}", webName, listName, Path.GetFileName(attachmentFileName));
        }
        else
        {
            attachmentPath = string.Format("/{0}/{1}/{2}/{3}", webName, listName, subfolder, Path.GetFileName(attachmentFileName));
        }
        var file = clientContext.Web.GetFileByServerRelativeUrl(attachmentPath);
        file.DeleteObject();
        clientContext.ExecuteQuery();
    }
}

Attach File to ListItem

public void AttachFileToListItem(string siteUrl, string webName, string listName, int itemId, string fileName, bool overwrite)
{
    using (ClientContext clientContext = new ClientContext(siteUrl))
    {
        FileStream fileStream = new FileStream(fileName, FileMode.Open);
        string attachmentPath = string.Format("/{0}/Lists/{1}/Attachments/{2}/{3}", webName, listName, itemId, Path.GetFileName(fileName));
        File.SaveBinaryDirect(clientContext, attachmentPath, fileStream, overwrite);
    }
}

Download File from ListItem

The following code snippet shows how to download file that is attached with list item.

public void DownloadAttachedFileFromListItem(string siteUrl, string webName, int itemId, string attachmentName, string listName, string downloadLocation)
{
    using (ClientContext clientContext = new ClientContext(siteUrl))
    {
        string attachmentPath = string.Format("/{0}/lists/{1}/Attachments/{2}/{3}", webName, listName, itemId, Path.GetFileName(attachmentName));
        var fileInformation = File.OpenBinaryDirect(clientContext, attachmentPath);
        IList<byte> content = new List<byte>();
        int b;
        while ((b = fileInformation.Stream.ReadByte()) != -1)
        {
            content.Add((byte)b);
        }
        var downloadFileName = Path.Combine(downloadLocation, attachmentName);
        System.IO.File.WriteAllBytes(downloadFileName, content.ToArray());
        fileInformation.Stream.Close();
    }
}

Delete Attached File From ListItem

The following code shows how to delete a file that is attached with list item.

public void DeleteAttachedFileFromListItem(string siteUrl, string webName, int itemId, string attachmentFileName, string listName)
{
    using (ClientContext clientContext = new ClientContext(siteUrl))
    {
        //http://siteurl/lists/[listname]/attachments/[itemid]/[filename]
        string attachmentPath = string.Format("/{0}/lists/{1}/Attachments/{2}/{3}", webName, listName, itemId, Path.GetFileName(attachmentFileName));
        var file = clientContext.Web.GetFileByServerRelativeUrl(attachmentPath);
        file.DeleteObject();
        clientContext.ExecuteQuery();
    }
}