Login failed for user ''. using UserAssignedManagedIdentity while fetching data from AzureSQL - azure

Question

I have created a Managed Identity (User Assigned) using Azure portal.
I attached that MSI with Azure App Service
Added appropriate permissions for the MSI at Azure SQL (Database)
In this implementation I am using Microsoft.EntityFrameworkCore version 2.2.6
I have the following code :
IDBAuthTokenService.cs
public interface IDBAuthTokenService
{
Task<string> GetTokenAsync();
}
AzureSqlAuthTokenService.cs
public class AzureSqlAuthTokenService : IDBAuthTokenService
{
public readonly IConfiguration _configuration;
public AzureSqlAuthTokenService(IConfiguration configuration)
{
_configuration = configuration ?? throw new ArgumentNullException(nameof(configuration));
}
public async Task<string> GetTokenAsync()
{
var credential = new DefaultAzureCredential(new DefaultAzureCredentialOptions{ManagedIdentityClientId = _configuration[C.AppKeys.UserAssignedClientId]});
var tokenRequestContext = new TokenRequestContext(new[]{_configuration[C.AppKeys.AzureSQLResourceId]});
var token = await credential.GetTokenAsync(tokenRequestContext, default);
return token.Token;
}
}
TestDbContext.cs:
public partial class TestDbContext : DbContext
{
public TestDbContext()
{
}
public TestDbContext(IDBAuthTokenService tokenService, DbContextOptions<TestDbContext> options) : base(options)
{
var connection = this.Database.GetDbConnection() as SqlConnection;
connection.AccessToken = tokenService.GetTokenAsync().Result;
}
public virtual DbSet<HealthCheckData> HealthCheckData { get; set; }
}
TestReportServiceProvider.cs
public class TestReportServiceProvider : IReportService
{
private readonly TestDbContext _objDBContext;
public TestReportServiceProvider(TestDbContext objDBContext)
{
_objDBContext = objDBContext;
}
public dynamic GetDataDetails(ReportDTO filters)
{
var response = new TestReponseExcelDto();
var ds = new DataSet();
using (var connection = new SqlConnection(_objDBContext.Database.GetDbConnection().ConnectionString))
{
connection.Open();
using (var command = new SqlCommand())
{
command.Connection = connection;
command.CommandType = CommandType.StoredProcedure;
command.CommandText = "[CR].[LoadProcedureDetailPopup]";
using (var sda = new SqlDataAdapter())
{
sda.SelectCommand = command;
sda.Fill(ds);
}
}
connection.Close();
}
if (ds.Tables.Count > 0)
{
response.Data = GetData(ds.Tables[0]);
response.TotalEngagements = response.Data.Select(d => d.TestReviewId).Distinct().Count();
}
return response;
}
}
In the above code while debugging I found error: Login failed for user ''. just after the control passes the code snippet connection.Open();. Even though the AccessToken was setup at the constructor within the TestDbContext , in this case I noticed that it is assigned with null value.
I added the below code before opening the connection and it started working fine as expected:
connection.AccessToken = ((SqlConnection)_objDBContext.Database.GetDbConnection()).AccessToken;
Even though my fix is solving the issue, I wanted to know whether it is correct way of doing it or are there better ways to manage it.
Can anyone help me to resolve this issue?