(Mono C#) Microsoft Graph OAuth2 Client Credentials Grant Flow

Demonstrates how to get a Microsoft Graph access token using the Client Credentials Grant Flow.

You can use the OAuth 2.0 client credentials grant specified in RFC 6749, sometimes called two-legged OAuth, to access web-hosted resources by using the identity of an application. This type of grant is commonly used for server-to-server interactions that must run in the background, without immediate interaction with a user. These types of applications are often referred to as daemons or service accounts.

For more information, see https://docs.microsoft.com/en-us/azure/active-directory/develop/v2-oauth2-client-creds-grant-flow

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// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

Chilkat.Http http = new Chilkat.Http();

Chilkat.HttpRequest req = new Chilkat.HttpRequest();
req.AddParam("client_secret","CLIENT_SECRET");
req.AddParam("client_id","CLIENT_ID");
// Don't know if the scopes valid for the client credentials grant are different than the scopes for the 3-legged Authorization Code Grant...
req.AddParam("scope","https://graph.microsoft.com/.default");
req.AddParam("grant_type","client_credentials");

// Use your own tenant ID, for example 4d8fdd66-66d1-43b0-ae5c-e31b4b7de5cd
string url = "https://login.microsoftonline.com/TENANT_ID/oauth2/v2.0/token";
Chilkat.HttpResponse resp = http.PostUrlEncoded(url,req);
if (http.LastMethodSuccess != true) {
    Debug.WriteLine(http.LastErrorText);
    return;
}

int statusCode = resp.StatusCode;
Debug.WriteLine("Response status code = " + Convert.ToString(statusCode));

Chilkat.JsonObject json = new Chilkat.JsonObject();
json.Load(resp.BodyStr);

json.EmitCompact = false;
Debug.WriteLine(json.Emit());

// Sample successful output:

// {
//   "token_type": "Bearer",
//   "expires_in": 3599,
//   "ext_expires_in": 3599,
//   "access_token": "eyJ0eX...K0jOERg"
// }

if (statusCode == 200) {
    json.WriteFile("qa_data/tokens/msGraphClientCredentialsToken.json");
    Debug.WriteLine("Success.");
}
else {
    Debug.WriteLine("Failed.");
}