detNet RestAPI Cognite SDK example

Hi @samirhaj! To use the CDF .NET SDK you will first need to use authenticate against your Identity Provider (IdP) to acquire a valid token. If you are using an Azure Active Directory (AAD), you can use the MSAL .NET library for this purpose.

Here’s a minimal C# example that reads the AAD and associated CDF variables from environment variables, initiate an interactive flow to acquire the token and uses the token to instantiate the CDF client. If you refer to the MSAL documentation, it’s straightforward to extend this example to other authentication flows.

string clientId = System.Environment.GetEnvironmentVariable("CLIENT_ID");
string tenantId = System.Environment.GetEnvironmentVariable("TENANT_ID");
string cluster = System.Environment.GetEnvironmentVariable("CDF_CLUSTER");
string project = System.Environment.GetEnvironmentVariable("CDF_PROJECT");

var scopes = new List<string>{ $"https://{cluster}.cognitedata.com/.default" };

var app = PublicClientApplicationBuilder
    .Create(clientId)
    .WithAuthority(AzureCloudInstance.AzurePublic, tenantId)
    .WithRedirectUri("http://local host")
    .Build();

AuthenticationResult result = await app.AcquireTokenInteractive(scopes).ExecuteAsync();
string accessToken = result.AccessToken;

var httpClient = new HttpClient();
var client = Client.Builder.Create(httpClient)
    .SetAppId("testNotebook")
    .AddHeader("Authorization", $"Bearer {accessToken}")
    .SetProject(project)
    .SetBaseUrl(new Uri($"https://{cluster}.cognitedata.com"))
    .Build();

Be mindful that I had to separate the words local and host, as this is a word that’s currently not allowed in the Cognite Hub.

Once you have instantiated a client, you can fetch some time series datapoints. Here’s a minimal example on how to do fetch the last 7 days of data from a time series with externalId = "pi:160704" with 1h granularity:

var res = await client.DataPoints.ListAsync(new DataPointsQuery{
    Start = "7d-ago",
    End = "now",
    Items = new List<DataPointsQueryItem> {
        new DataPointsQueryItem {
            ExternalId = "pi:160704",
            Aggregates = new List<string> { "average" },
            Granularity = "1h",
            Limit = 10_000
        }
    }
});
var ts = res.Items[0];
var dps = ts.AggregateDatapoints.Datapoints;

In this case, declaring the client with var or CogniteSdk.Client does not make a difference. The last command Build() creates an instance of the client that you can use to fetch time series data points as with the example above.

Hi @Anita Hæhre : There were some specifics regarding our own company interface with Cognite, so I continued the discussion with @Everton Colling in the private session. 

Hi @Everton Colling 

Thanks for your reply.

My ultimate goal is to convert the data that I pull out from cognite interface into a csv file (in which each of the data type with its ExternalId in one column of the csv and DateTime in the first column), so I would rather have the output result that looks like this now;

{ DateTime = 3/23/2023 21:00:00, Average = 13.713887271148339 }

{ DateTime = 3/23/2023 22:00:00, Average = 13.662878633528655 }

…

into the format that I won’t see the words “DateTime = “ and “Average = ” in each row of data. So I mean something similar to the following if possible?

DateTime                     Average

3/23/2023 21:00:00      13.713887271148339

3/23/2023 22:00:00       13.662878633528655

.

.

.

One other question I have is that in the console.writeline() of the code, there is no string “DateTime = “ or “Average = “, so I wonder how these words was printed out to the console?

Best regards.

Ok, Thanks for your reply.

One more question here: to set how often we want to fetch data for us, should we configure the Granularity parameter or ... ? For example, if I want the data for every 1 sec or 10 sec or 1 minute. I tried to put Granularity to be “0.5h” but it crashed. 

Could you please advise?

Best regards.