Error 403- When trying to retrieve single entity from Azure Table Storage using IHttpClientFactory

I think the problem is in your Authorization header.

Here is your code:

Client.DefaultRequestHeaders.TryAddWithoutValidation("Authorization", sas);

I think you should change it to:

Client.DefaultRequestHeaders.TryAddWithoutValidation("Authorization", $"Bearer {sas}");

Otherwise the code looks righteous.

I believe the reason you are getting this error is because you are using two different dates in your code.

You are getting the current date in getRequestHeaders method and then a different date in getAuthToken. This would cause the authorization header mismatch.

I would recommend modifying getAuthToken method and pass the date/time value computed in getRequestHeaders method.

Try the following code:

    public HttpClient getRequestHeaders(string requestType, HttpClient Newrequest, string storageAccount, string accessKey, string resource, string partitionKey, string rowKey, int Length = 0)
    {
        HttpClient Client = Newrequest;
        
        var RequestDateString = DateTime.UtcNow.ToString("R", CultureInfo.InvariantCulture);
        if (Client.DefaultRequestHeaders.Contains("x-ms-date"))
            Client.DefaultRequestHeaders.Remove("x-ms-date");
        Client.DefaultRequestHeaders.Add("x-ms-date", RequestDateString);
        
        var requestUri = @"https://" + storageAccount + ".table.core.windows.net/" + resource;

        Client.DefaultRequestHeaders.Accept.Clear();
        Client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

        if (Client.DefaultRequestHeaders.Contains("x-ms-version"))
            Client.DefaultRequestHeaders.Remove("x-ms-version");

        Client.DefaultRequestHeaders.Add("x-ms-version", "2015-12-11");

        if (Client.DefaultRequestHeaders.Contains("DataServiceVersion"))
            Client.DefaultRequestHeaders.Remove("DataServiceVersion");
        Client.DefaultRequestHeaders.Add("DataServiceVersion", "3.0;NetFx");

        if (Client.DefaultRequestHeaders.Contains("MaxDataServiceVersion"))
            Client.DefaultRequestHeaders.Remove("MaxDataServiceVersion");
        Client.DefaultRequestHeaders.Add("MaxDataServiceVersion", "3.0;NetFx");


        if (Client.DefaultRequestHeaders.Contains("Authorization"))
            Client.DefaultRequestHeaders.Remove("Authorization");
        var sas =  getAuthToken(Client, storageAccount, accessKey, resource, RequestDateString, partitionKey, rowKey);
        Client.DefaultRequestHeaders.TryAddWithoutValidation("Authorization", sas);

        return Client;
    }
            
public string getAuthToken(HttpClient request, string storageAccount, string accessKey, string resource, string requestDateString, string partitionKey, string rowKey)
{
    try
    {
        string sAuthTokn = "";

        string stringToSign = requestDateString + "\n";

        stringToSign += "/" + storageAccount + "/" + resource +  "(PartitionKey='" + partitionKey + "',RowKey='" + rowKey + "')";

        HMACSHA256 hasher = new HMACSHA256(Convert.FromBase64String(accessKey));

        sAuthTokn = "SharedKeyLite " + storageAccount + ":" + Convert.ToBase64String(hasher.ComputeHash(Encoding.UTF8.GetBytes(stringToSign)));

        return sAuthTokn;
    }
    catch (Exception ex)
    {
        throw ex;
    }
}

public async Task<string> GetEntityByID(string department, string id)
{
    EmployeeDetails emp = new EmployeeDetails();
    string storageAccount = "sample";
    string resourcePath = "SampleAzureTableStorage";
    string accessKey = "<sample>";
    string uri = @"https://" + storageAccount + ".table.core.windows.net/" + resourcePath + "/";
    var request = _httpClientFactory.CreateClient();
    request = getRequestHeaders("GET", request, storageAccount, accessKey, resourcePath, department, id);
    
    try
    {
        var httpResponseMessage = await request.GetAsync(uri + "(PartitionKey='" + department + "',RowKey='" + id + "')");
        httpResponseMessage.EnsureSuccessStatusCode();
        return await httpResponseMessage.Content.ReadAsStringAsync();
        
    }
    catch (WebException ex)
    {
        throw ex;
    }
}