Sending mail using GraphServiceClient - microsoft-graph-api

Question

I wrote a dll using .NET C# that was supposed to send emails using graph API.
When I'm using the dll from a console application - everything works as expected: if the user is logged in the mail is sent, and if not - a screen pops up to connect.
But, when I try to use the same dll in WinForms, the program stuck.
Any idea why?
This is my code:
var options = new PublicClientApplicationOptions {
ClientId = clientId,
TenantId = tenantId,
RedirectUri = "https://login.microsoftonline.com/common/oauth2/nativeclient",
};
if (application == null) {
application = PublicClientApplicationBuilder.CreateWithApplicationOptions(options).WithAuthority(AzureCloudInstance.AzurePublic, ClientSecretOrTenantId).Build();
}
string token = "";
GraphServiceClient graphServiceClient = new GraphServiceClient(new DelegateAuthenticationProvider(async(requestMessage) =>{
token = await GetToken();
requestMessage.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
}));
Recipient recipient = new Recipient();
recipient.EmailAddress = new EmailAddress();
recipient.EmailAddress.Address = toAddress;
List < Recipient > recipients = new List < Recipient > ();
recipients.Add(recipient);
var message = new Message {
Subject = subject,
Body = new ItemBody {
ContentType = isHtml ? BodyType.Html: BodyType.Text,
Content = bodyText,
},
ToRecipients = recipients,
};
try {
await graphServiceClient.Me.SendMail(message, false).Request().PostAsync(); // get stuck here
} catch(ServiceException) {
graphServiceClient = new GraphServiceClient(new DelegateAuthenticationProvider(async(requestMessage) =>{
token = await GetToken();
requestMessage.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
}));
await graphServiceClient.Me.SendMail(message, false).Request().PostAsync();
}

Answer 1

I'd hazard a guess that you're trying to make the asynchronous method synchronous by calling SendEmailAsync(email).Wait() in your (button click?) event handler, which is causing a WinForms UI thread lock.
The solution is to mark your event handler as async void and await your method in the event handler code.