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Issue Retrieving Bearer Tokens for Business Central API Access in a C# Method

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Posted on by Kevin Fernandez

Hello,

I am attempting to access the Business Central API from a C# application. The program successfully connects to BC and gets a token, but the request using that token fails with StatusCode: 401, ReasonPhrase: 'Unauthorized'.

This process works fine in Postman, and if I copy the token from the working Postman and paste it into the C# code, the API request works fine. The token retrieved from BC appears to be much shorter than the one that is obtained in Postman.

I'm guessing it's something simple I am missing, but I can find what that might be.

Here is my code.

static async Task RunApiTest()
{
try
{
string bearerToken = "";
string ClientId = "(removed)";
string ClientSecret = "(removed)";
string TenantId = "(removed)";

string tokenUrl = $"https://login.microsoftonline.com/{TenantId}/oauth2/v2.0/token";

HttpClient client = new HttpClient();
var content = new StringContent("grant_type=client_credentials" +
"&scope=https://api.businesscentral.dynamics.com/.default" +
"&client_id=" + HttpUtility.UrlEncode(ClientId) +
"&client_secret=" + HttpUtility.UrlEncode(ClientSecret));
content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/x-www-form-urlencoded");
var response = await client.PostAsync(tokenUrl, content);

if (response.IsSuccessStatusCode)
{
var tokenContent = await response.Content.ReadAsStringAsync();
var tokenResponse = Newtonsoft.Json.JsonConvert.DeserializeObject<TokenResponse>(tokenContent);
bearerToken = tokenResponse.AccessToken;
string apiUrl = $"https://api.businesscentral.dynamics.com/v2.0/(removed)/Sandbox/api/v2.0/companies((removed))/customers";
HttpClient httpClient = new HttpClient();
httpClient.DefaultRequestHeaders.Add("Authorization", "Bearer " + bearerToken);
httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
var apiRespponse = await httpClient.GetAsync(apiUrl);
if (apiRespponse.IsSuccessStatusCode)
{
string resultString = await httpClient.GetStringAsync(apiUrl);
}
}
}
catch (Exception ex)
{
Console.WriteLine(ex.ToString());
}
}
public class TokenResponse
{
[Newtonsoft.Json.JsonProperty("access_token")]
public string AccessToken { get; set; }
}

Thanks!

Categories:

Dynamics 365 Business Central

All responses (3)

Answers (0)

Suggested answer

Dharmendra_Chavda 260 on at

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Issue Retrieving Bearer Tokens for Business Central API Access in a C# Method

Hello,

The below code is working fine for me.

try this one.

static async Task Main1(string[] args)
{
string ClientId = "(removed)";
string ClientSecret = "(removed)";
string TenantId = "(removed)";
string URL = "https://login.microsoftonline.com/" + TenantId + "/oauth2/v2.0/token";
HttpClient client = new HttpClient();
var content = new StringContent("grant_type=client_credentials" +
"&scope=https://api.businesscentral.dynamics.com/.default" +
"&client_id=" + HttpUtility.UrlEncode(ClientId) +
"&client_secret=" + HttpUtility.UrlEncode(ClientSecret));
content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/x-www-form-urlencoded");
var response = await client.PostAsync(URL, content);
if (response.IsSuccessStatusCode)
{
JObject Result = JObject.Parse(await response.Content.ReadAsStringAsync());
string BearerToken = Result["access_token"].ToString();
//Token Generated

// API CAll
var client1 = new RestClient("https://api.businesscentral.dynamics.com/v2.0/TenantId/Sandbox/ODataV4/Company('CRONUS%20IN')/ItemCard('1896-S')");
client1.Timeout = -1;
var request = new RestRequest(Method.GET);
request.AddHeader("Authorization", "Bearer " + BearerToken);
IRestResponse response1 = client1.Execute(request);
Console.WriteLine(response1.Content);
}
else
{
Console.WriteLine(response.Content);
}

}

If it works then mark a verified answer.
gdrenteria 12,290 Most Valuable Professional on at

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Issue Retrieving Bearer Tokens for Business Central API Access in a C# Method

Hi Have you tried configuring the application in the admin center?

Best

GR
Suggested answer

YUN ZHU 74,036 Super User 2024 Season 2 on at

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Issue Retrieving Bearer Tokens for Business Central API Access in a C# Method

Hi, Sorry, I'm not sure. It seems to be the problem in this part. If it is written as fixed, can it pass authorization?

Here is the Oauth test I did in Power Automate, hope it can give you some hints.

https://yzhums.com/33195/

Thanks.

ZHU