To automatically refresh the token in an ASP.NET Core application for a Power BI report, you can implement an approach that fetches a new access token before the current one expires. Here are some steps you can follow:
1. Implement a Token Refresh Method
Set up a method to retrieve a new token from Azure Active Directory (AAD) when the existing token expires. This usually involves setting up a method to request a new token using the client credentials or authorization flow.
csharp
public async Task<string> GetAccessToken()
{
var app = ConfidentialClientApplicationBuilder.Create(clientId)
.WithClientSecret(clientSecret)
.WithAuthority(new Uri(authority))
.Build();
var scopes = new string[] { "https://analysis.windows.net/powerbi/api/.default" };
AuthenticationResult result = await app.AcquireTokenForClient(scopes).ExecuteAsync();
return result.AccessToken;
}
2. Use a Timer or Background Service
Set up a background task or timer in ASP.NET Core to refresh the token at regular intervals. A timer could be set to request a new token just before the old token expires. Alternatively, ASP.NET Core’s `IHostedService` can be used to handle token refresh in the background.
For example:
csharp
public class TokenRefreshService : IHostedService, IDisposable
{
private Timer _timer;
private readonly TokenProvider _tokenProvider; // Your service to get tokens
public TokenRefreshService(TokenProvider tokenProvider)
{
_tokenProvider = tokenProvider;
}
public Task StartAsync(CancellationToken cancellationToken)
{
_timer = new Timer(RefreshToken, null, TimeSpan.Zero, TimeSpan.FromMinutes(50)); // Set before expiration
return Task.CompletedTask;
}
private async void RefreshToken(object state)
{
await _tokenProvider.RefreshToken(); // Method to refresh and store token
}
public Task StopAsync(CancellationToken cancellationToken)
{
_timer?.Change(Timeout.Infinite, 0);
return Task.CompletedTask;
}
public void Dispose()
{
_timer?.Dispose();
}
}
3. Configure Token Refresh in the Frontend (JavaScript/HTML)
In your frontend code, handle token expiration errors by requesting a new token. For instance, if you receive the `ClientError_TokenExpired` error, refresh the token and re-initialize the Power BI embedded report.
javascript
function refreshReport() {
powerbi.get(reportContainer).embedConfig.accessToken = '<new_token>'; // Assign refreshed token
powerbi.get(reportContainer).refresh(); // Reload the report
}
4. Store the Token Securely and Update It
When you obtain a new token, store it securely (for example, in-memory cache) and ensure all subsequent requests use the latest token. Update your embed configurations or any other services that use this token.
Additional Tips
- Token Lifetime: Check your access token's lifetime and adjust the refresh frequency accordingly. For example, if the token lasts 60 minutes, you might refresh every 50 minutes.
- Use Azure AD Library: Use the Microsoft Authentication Library (MSAL) to manage tokens if possible; it includes built-in token caching and refresh handling.
Let me know if you need more details on any specific part!
