How to use ManagementClient.ManagementCertificates.CreateAsync to upload a cert

I am looking for a way to upload a certificate to azure management certificates

var p = new ManagementCertificateCreateParameters();         
p.Data = new X509Certificate2(@"c:\test\test.pfx", "test").Export(X509ContentType.Cert, "test")       
await client.ManagementCertificates.CreateAsync(p);

But seems it doesn't work.  When my program execute

      await client.ManagementCertificates.CreateAsync(p);

It just hang there and never return

Did i do something wrong?