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Posted 21 Apr 2013

How to Get SharePoint Client Context in SharePoint Apps (Provider Hosted / SharePoint Access ) in CSOM (Client Side Object Model)

, 21 Apr 2013
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How to get SharePoint client context in SharePoint Apps in CSOM


The first step of app development is to correctly get access to SharePoint client context. I have struggled to develop a simple model to initialize the SharePoint Client context. Most of the App development includes ASP Master pages. So I need to figure out a working model for app development.

First, you need to know how SharePoint offers the contextString. contextString offers when SharePoint gets redirected from appredirect.aspx URL.


At that point, we need to capture the contextString and generate either AccessToken or RefreshToken and save it for accessing the SharePoint Client Context at a later time. Otherwise, it will result in generating the error The parameter 'token' cannot be a null or empty string (This is a nasty error which drove me crazy.).

Normally AccessToken is valid for 12 hours and RefreshToken is valid for 6 months.

In my approach, I used another key which is called as CacheKey to identify the user uniquely. Therefore I use this value to maintain a cookie based on the user.

Reference: Tips and FAQs: OAuth and remote apps for SharePoint 2013

The following shows my approach to do this. If you have a master page, you need to put the code in the onInit() rather than page load.

protected void Page_Load(object sender, EventArgs e)
   var key = Session["CashKey"];

   // sharepoint url (app hosted url)
   var hostWeb = Page.Request["SPHostUrl"];

   // Sharepoint url with app Title (app deployed sp url)
   Uri SharePointUri = new Uri(hostWeb + "/SharePointApp1/");

   // This is first time the app is running
   if (key == null)
       // get the TokenString
       var contextTokenString = TokenHelper.GetContextTokenFromRequest(Page.Request);
       // Get the contexttoken by passing the token string
       var contextToken = TokenHelper.ReadAndValidateContextToken
       		(contextTokenString, Request.Url.Authority);

       //Since some browsers does not support cookie name more than 40 chars
       // Im taking first 40 chars
       var cookieName = contextToken.CacheKey.Substring(0, 40);

       //Add User specific cookie name to the Session
       Session.Add("CashKey", cookieName);

       // Get the Refresh Token
       var refreshToken = contextToken.RefreshToken;
       // Add the cookie value (refresh Token)
       Response.Cookies.Add(new HttpCookie(cookieName, refreshToken));

       // USER already in the application,  means it is not getting redirect from the appRedirect
       // So contextstring is null 

This is code for button click.

protected void Button1_Click(object sender, EventArgs e)
    // sharepoint url (app hosted url)
    var hostWeb = Page.Request["SPHostUrl"];

    // Sharepoint url with app name (app deployed sp url)
    Uri SharePointUri = new Uri(hostWeb + "/SharePointApp1/");

    // Get the cookie name from the session
    var key = Session["CashKey"] as string;
    // Get the refresh token from the cookie
    var refreshToken = Request.Cookies[key].Value;

    //Get the access Token By passing refreshToken
    // 00000003-0000-0ff1-ce00-000000000000 is principal name for SP2013 it is unique
    var accessToken = TokenHelper.GetAccessToken(refreshToken,
        SharePointUri.Authority, TokenHelper.GetRealmFromTargetUrl(SharePointUri));

    // Access the Sharepoint Do your work
    using (var clientContext = TokenHelper.GetClientContextWithAccessToken
    ("", accessToken.AccessToken))
        clientContext.Load(clientContext.Web, web => web.Title);

Note: In the middle of the app, if the context is broken due to expiration or some other case you need to initialize the app from the AppRedirect, therefore you can:

var hostWeb = Page.Request["SPHostUrl"];
var val = TokenHelper.GetAppContextTokenRequestUrl(hostWeb, Server.UrlEncode(Request.Url.ToString()));


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Sri Lanka Sri Lanka
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Comments and Discussions

QuestionUnable to deploy provider hosted app in to another machine Pin
Sivadutta2-Mar-14 16:32
memberSivadutta2-Mar-14 16:32 

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