RESTful API Calls to SharePoint Online

Question

There are many great articles describing how to return results from a list in SharePoint Online using the SharePointOnlineCredentials class to pass your credentials such as the link below.

Make a RESTful API Call to SharePoint Online from Console program

However, I'd like to make a POST call to add an item to a SharePoint list and can't seem to find any documentation online. I'm using C# in a Console App. Can anyone help with this? Thanks.

Answer 1

For REST operations in C# I recommend you to use extremely useful library called RestSharp (more than 1M downloads for last year).
So you need to install it first from nuget:

Install-Package RestSharp 

Then you need to create your credentials object, for example in a following way:

var passWord = new SecureString();
foreach (char c in "mypass") passWord.AppendChar(c);
var creds = new SharePointOnlineCredentials("[email protected]", passWord);
var baseUrl = "https://sp.sharepoint.com/sites/dev/";

Now if you need to get all list items:

var resultJSON = GetItems(creds, baseUrl);

And GetItems method:

private static string GetItems(SharePointOnlineCredentials creds, string baseUrl)
{
    var client = new RestClient(baseUrl + "_api/");
    var getItemsRequest = new RestRequest("web/lists/getbytitle('coolist')/items", Method.GET);
    getItemsRequest.AddHeader("Accept", "application/json");

    //authentication cookie
    client.CookieContainer = new CookieContainer();
    client.CookieContainer.SetCookies(new Uri(baseUrl), creds.GetAuthenticationCookie(new Uri(baseUrl)));

    //return just JSON string, but you can deserialize to strongly type object with 
    //client.Execute<MyClass>(getItemsRequest)
    return client.Execute(getItemsRequest).Content;
}  

For POST you need x-requestdigest first:

var digest = GetRequestDigest(creds, baseUrl);
resultJSON = CreateItem(creds, baseUrl, digest["FormDigestValue"]); 

GetRequestDigest and CreateItem:

 private static dynamic GetRequestDigest(SharePointOnlineCredentials creds, string baseUrl)
{
    var client = new RestClient(baseUrl + "_api/");
    var digestRequest = new RestRequest("contextinfo", Method.POST);
    digestRequest.AddHeader("Accept", "application/json");

    //authentication cookie
    client.CookieContainer = new CookieContainer();
    client.CookieContainer.SetCookies(new Uri(baseUrl), creds.GetAuthenticationCookie(new Uri(baseUrl)));

    //I'm using dynamic jsut for demo, it's better to use some strongly typed class  
    return client.Execute<dynamic>(digestRequest).Data;
}

private static string CreateItem(SharePointOnlineCredentials creds, string baseUrl, string digest)
{
    var client = new RestClient(baseUrl + "_api/");
    var createItemRequest = new RestRequest("web/lists/getbytitle('coolist')/items", Method.POST);
    //createItemRequest.Parameters.Clear();
    createItemRequest.AddHeader("Accept", "application/json");
    createItemRequest.AddHeader("Content-Type", "application/json;odata=verbose");
    //NOTE - digest added here
    createItemRequest.AddHeader("X-RequestDigest", digest);

    //authentication cookie
    client.CookieContainer = new CookieContainer();
    client.CookieContainer.SetCookies(new Uri(baseUrl), creds.GetAuthenticationCookie(new Uri(baseUrl)));

    //add body with item metdata, you can use javascript serialization if you want
    createItemRequest.AddParameter("application/json;odata=verbose", "{ '__metadata': { 'type': 'SP.Data.CoolistListItem' }, 'Title': 'TESTTESTS'}", ParameterType.RequestBody);

    return client.Execute(createItemRequest).Content;
}