How to attach a attachment file to a list item using REST API in SharePoint 2013

Question

I'd like to ask experts.

Dose anyone know how to attach a attachment file to a list item using REST API in SharePoint 2013 ? I searched the bellow document. But there is no information about upload a file as list item's attachments.

http://msdn.microsoft.com/en-us/library/fp142386.aspx

Additional info:

I found the bellow article.

http://chuvash.eu/2013/02/20/rest-api-add-a-plain-text-file-as-an-attachment-to-a-list-item/

According to the article, it's enable to upload a attachment file to a list item using bellow Javascript code. I'd like to use C#. I'm trying now, but I still didn't success.

var content = "Hello, this text is inside the file created with REST API";
var digest = $("#__REQUESTDIGEST").val();
var composedUrl = "/_api/web/lists/GetByTitle('List1')/items(1)/AttachmentFiles/add(FileName='readme.txt')";
$.ajax({
    url: composedUrl,
    type: "POST",
    data: content,
    headers: {        
        "X-RequestDigest": digest
    }
})

Answer 1

There are a several approaches how to consume SharePoint REST API using .NET,some of them are listed below:

• HttpClient - Provides a base class for sending HTTP requests and receiving HTTP responses from a resource identified by a URI. ( .NET Framework 4.5 )
• WebClient - provides common methods for sending data to and receiving data from a resource identified by a URI. ( .NET Framework 1.1 )
• HttpWebRequest - provides an HTTP-specific implementation of the WebRequest class, more low-level then the previous ones

All of them allows to perform CRUD operations in SharePoint Online/SharePoint 2013 using REST interface.

SPWebClient class demonstrates how to perform CRUD operations using WebClient .

How to add attachment file via SharePoint REST API

The following example demonstrates how to add attachment file to List in SharePoint Online:

var credentials = new SharePointOnlineCredentials(userName, securePassword);
AddAttachmentFile(webUrl, credentials, "Nokia Offices", 1, @"c:\upload\Nokia Head Office in Espoo.jpg");


public static void AddAttachmentFile(string webUrl,ICredentials credentials,string listTitle,int itemId,string filePath)
{
        using (var client = new SPWebClient(new Uri(webUrl),credentials))
        {
            var fileContent = System.IO.File.ReadAllBytes(filePath);
            var fileName = System.IO.Path.GetFileName(filePath);
            var endpointUrl = string.Format("{0}/_api/web/lists/GetByTitle('{1}')/items({2})/AttachmentFiles/add(FileName='{3}')", webUrl,listTitle,itemId,fileName);
            client.UploadFile(new Uri(endpointUrl), fileContent);
        }
}

Dependencies:

• Utilizes SPWebClient class which represents a wrapper for WebClient
• Json.NET library dependency

Answer 2

Try to use this:

var executor = new SP.RequestExecutor(appweburl);
var digest = $("#__REQUESTDIGEST").val();
var content = "Hello, this text is inside the file created with REST API";

executor.executeAsync(
{
url: appweburl +           "/_api/web/lists/getbytitle('List1')/items(1)/AttachmentFiles/add(FileName='readme.txt)",
method: "POST",
body: content,
headers: {
          "X-RequestDigest": digest
         },
success: function(data) {
         toastr.success('Document attached successfully.');
         },
error: function(err) {
         toastr.error('Oops! Document attached created fail.');
         }
}
);