I fixed it.
I used executeScalar instead of counting in a dataset:
Dim sqlConnection2 As New SqlConnection("Data Source=(localdb)\v11.0;Initial Catalog=tempdb;Integrated Security=True")
Dim attempts As String
Dim comm As New SqlCommand("SELECT [Count] = COUNT(*) FROM ReverseTransferConsent_Attempt WHERE IPaddress = @IPaddress AND CreatedDate > DATEADD(MINUTE, -30, GETDATE())", sqlConnection1)
comm.Parameters.AddWithValue("@IPaddress", IPaddress)
comm.Connection = sqlConnection2
If Page.IsValid Then
sqlConnection2.Open()
attempts = Convert.ToString(comm.ExecuteScalar())
sqlConnection2.Close()
Label1.Text = attempts