Azure Function C# - Http Trigger throws System.Web.Extensions could not be found

Problem is caused by the difference of Function runtime.

The tutorial you follow creates function on ~1 runtime where code targets at .NET Framework , while the one you create is on ~2 runtime which runs on .NET Core env. When we create a new Function app its runtime is set to ~2 by default now.

Solution is to set FUNCTIONS_EXTENSION_VERSION to ~1 in Application settings on portal.

To achieve that in ~2 runtime, create a httptrigger in ~2 and replace the sample code with snippet below. Note you also have to add PBIE_TENANT_ID in Application settings with value get from Azure Active Directory> Properties>Directory ID.

#r "Newtonsoft.Json"

using System.Net;
using System.Text;
using Newtonsoft.Json;

static string resourceUrl = "https://analysis.windows.net/powerbi/api";
static string clientId = Environment.GetEnvironmentVariable("PBIE_CLIENT_ID");
static string username = Environment.GetEnvironmentVariable("PBIE_USERNAME");
static string password = Environment.GetEnvironmentVariable("PBIE_PASSWORD");
static string groupId = Environment.GetEnvironmentVariable("PBIE_GROUP_ID");
static string reportId = Environment.GetEnvironmentVariable("PBIE_REPORT_ID");
static string tenantId = Environment.GetEnvironmentVariable("PBIE_TENANT_ID");
static string tokenEndpoint = $"https://login.microsoftonline.com/{tenantId}/oauth2/token";

public static async Task<HttpResponseMessage> Run(HttpRequestMessage req, ILogger log)
{
    // Get access token 
    HttpClient authclient = new HttpClient();

    log.LogInformation(resourceUrl);
    log.LogInformation(tokenEndpoint);

    var authContent = new FormUrlEncodedContent(new[]
    {
        new KeyValuePair<string, string>("grant_type", "password"),
        new KeyValuePair<string, string>("username", username),
        new KeyValuePair<string, string>("password", password),
        new KeyValuePair<string, string>("client_id", clientId),
        new KeyValuePair<string, string>("resource", resourceUrl)
    });

    var accessToken = await authclient.PostAsync(tokenEndpoint, authContent).ContinueWith<string>((response) =>
    {
        log.LogInformation(response.Result.StatusCode.ToString());
        log.LogInformation(response.Result.ReasonPhrase.ToString());
        log.LogInformation(response.Result.Content.ReadAsStringAsync().Result);
        AzureAdTokenResponse tokenRes =
            JsonConvert.DeserializeObject<AzureAdTokenResponse>(response.Result.Content.ReadAsStringAsync().Result);
        return tokenRes?.AccessToken;
    });

    // Get PowerBi report url and embed token
    HttpClient powerBiClient = new HttpClient();
    powerBiClient.DefaultRequestHeaders.Add("Authorization", $"Bearer {accessToken}");

    log.LogInformation(accessToken);

    var embedUrl =
        await powerBiClient.GetAsync($"https://api.powerbi.com/v1.0/myorg/groups/{groupId}/reports/{reportId}")
        .ContinueWith<string>((response) =>
        {
            log.LogInformation(response.Result.StatusCode.ToString());
            log.LogInformation(response.Result.ReasonPhrase.ToString());
            PowerBiReport report =
                JsonConvert.DeserializeObject<PowerBiReport>(response.Result.Content.ReadAsStringAsync().Result);
            return report?.EmbedUrl;
        });

    var tokenContent = new FormUrlEncodedContent(new[]
    {
        new KeyValuePair<string, string>("accessLevel", "view")
    });

    var embedToken = await powerBiClient.PostAsync($"https://api.powerbi.com/v1.0/myorg/groups/{groupId}/reports/{reportId}/GenerateToken", tokenContent)
        .ContinueWith<string>((response) =>
        {
            log.LogInformation(response.Result.StatusCode.ToString());
            log.LogInformation(response.Result.ReasonPhrase.ToString());
            PowerBiEmbedToken powerBiEmbedToken =
                JsonConvert.DeserializeObject<PowerBiEmbedToken>(response.Result.Content.ReadAsStringAsync().Result);
            return powerBiEmbedToken?.Token;
        });


    // JSON Response
    EmbedContent data = new EmbedContent
    {
        EmbedToken = embedToken,
        EmbedUrl = embedUrl,
        ReportId = reportId
    };
    string jsonp = "callback(" + JsonConvert.SerializeObject(data) + ");";

    // Return Response
    return new HttpResponseMessage(HttpStatusCode.OK)
    {
        Content = new StringContent(jsonp, Encoding.UTF8, "application/json")
    };

}

public class AzureAdTokenResponse
{
    [JsonProperty("access_token")]
    public string AccessToken { get; set; }
}

public class PowerBiReport
{
    [JsonProperty(PropertyName = "id")]
    public string Id { get; set; }

    [JsonProperty(PropertyName = "name")]
    public string Name { get; set; }

    [JsonProperty(PropertyName = "webUrl")]
    public string WebUrl { get; set; }

    [JsonProperty(PropertyName = "embedUrl")]
    public string EmbedUrl { get; set; }

    [JsonProperty(PropertyName = "datasetId")]
    public string DatasetId { get; set; }
}

public class PowerBiEmbedToken
{
    [JsonProperty(PropertyName = "token")]
    public string Token { get; set; }

    [JsonProperty(PropertyName = "tokenId")]
    public string TokenId { get; set; }

    [JsonProperty(PropertyName = "expiration")]
    public DateTime? Expiration { get; set; }
}

public class EmbedContent
{
    public string EmbedToken { get; set; }
    public string EmbedUrl { get; set; }
    public string ReportId { get; set; }
}