integrate office 365 with C# WebForms Applications

Question

Is there any support for WebForms C# Applications (non-MVC) ? or a work-around? If I want to integrate an existing mature C# webforms app with office 365 authentication and don’t want to have to rewrite the whole application.

Answer 1

To implement the OAuth authentication from Azure AD, we can write the code to redirect the user to the login page using the code below(From Login button click):

   {
        var authority = "https://login.microsoftonline.com";
        var tenant = "common";
        var authorizeSuffix = "oauth2";

        var EndPointUrl = String.Format("{0}/{1}/{2}/authorize?", authority, tenant, authorizeSuffix);

        var clientId = "";
        var redirectURL = "http://localhost:56384/auth.aspx";         
        var parameters = new Dictionary<string, string>
            {
                { "response_type", "code" },
                { "client_id", clientId },
                { "redirect_uri", redirectURL },
                { "prompt", "login"}
            };

        var list = new List<string>();

        foreach (var parameter in parameters)
        {
            if (!string.IsNullOrEmpty(parameter.Value))
                list.Add(string.Format("{0}={1}", parameter.Key, HttpUtility.UrlEncode(parameter.Value)));
        }
        var strParameters = string.Join("&", list);
        var requestURL=String.Concat(EndPointUrl,strParameters);

        Response.Redirect(requestURL);

    }

After the user sign-in the Azure AD, it will redirect to the redirectURL which we configed on the Azure. We can config it to the specific page to get the AUTH Code and request the token. Here is an example:

Auth.aspx:

   protected void Page_Load(object sender, EventArgs e)
    {
        var authority = "https://login.microsoftonline.com";
        var tenant = "common";
        var authorizeSuffix = "oauth2";
        var EndPointUrl = String.Format("{0}/{1}/{2}", authority, tenant, authorizeSuffix);

        var code = Request.QueryString["code"].ToString();

        var clientId = "";
        var resource = "https://graph.microsoft.com";
        var secrect = "";
        var redirectURL = "http://localhost:56384/auth.aspx";

        //Request access token
        var parameters = new Dictionary<string, string>
            {
                { "resource", resource},
                { "client_id", clientId },
                { "code",  code},
                { "grant_type", "authorization_code" },
                { "redirect_uri", redirectURL},
                { "client_secret",secrect}
            };


        var list = new List<string>();

        foreach (var parameter in parameters)
        {
            if (!string.IsNullOrEmpty(parameter.Value))
                list.Add(string.Format("{0}={1}", parameter.Key, HttpUtility.UrlEncode(parameter.Value)));
        }
        var strParameters = string.Join("&", list);


        var content = new StringContent(strParameters, Encoding.GetEncoding("utf-8"), "application/x-www-form-urlencoded");

        var client = new HttpClient();

        var url = string.Format("{0}/token", EndPointUrl);

        var response = client.PostAsync(url, content).Result;

        var text = response.Content.ReadAsStringAsync().Result;

        var result = JsonConvert.DeserializeObject(text) as JObject;

        var AccessToken = result.GetValue("access_token").Value<string>();
        var RefreshToken = result.GetValue("refresh_token").Value<string>();

        Session["accessToken"] = AccessToken;
        Session["refreshToken"] = AccessToken;


        //add code read the user info from access token for login in


    }

For the detail of Authorization Code Grant Flow you can refer to here

Update

Extract the user name form access token:

string accessToken = "";

byte[] data = Convert.FromBase64String(accessToken.Split('.')[1]);
string decodedString = Encoding.UTF8.GetString(data);

JToken token = JObject.Parse(decodedString);            
Console.WriteLine(token["name"].Value<string>());