我对下面的代码片段有点困惑。
当用户尝试注册培训时，代码会检查此用户是否已经注册了此课程。
如果为true，则我们定义的错误消息会引发异常。
我尝试将我的帐户用于测试目的，并且我不断收到我已经报名参加课程的消息，但事实并非如此。
我在这里缺少什么？
BEGIN
Declare @Counter INT
SELECT @Counter = COUNT(*)
FROM [Trainings]
WHERE UserId = @userId AND CourseID = @cosId AND LocationID = @locid AND dateId = @dat
IF @Counter > 0
BEGIN
--User has already signed up for this class.
RAISERROR ('You have already signed up for this training.',16,1)
RETURN
END
ELSE
BEGIN
Declare @SeatsAvailable INT
--User has not already signed up for this class, then check to see if seat is still available
SELECT @SeatsAvailable = (Select Seating_Capacity - (Select count(*) from tblTrainings where courseId = @cosId) from Locations WHERE LocationId = @Locid)
END
END
Protected Sub btnSAP_Click(ByVal sender As Object, ByVal e As System.Web.UI.ImageClickEventArgs) Handles btnSAP.Click
Dim userid = Session("userid")
Dim Conn As SqlConnection
Conn = New SqlConnection(ConfigurationManager.ConnectionStrings("DBConnectionString").ConnectionString)
Conn.Open()
Try
Dim cmd As SqlCommand = New SqlCommand("signUp", Conn)
cmd.CommandType = CommandType.StoredProcedure
cmd.Parameters.AddWithValue("@cosID", Request.QueryString("cosId"))
cmd.Parameters.AddWithValue("@locID", Request.QueryString("locid"))
cmd.Parameters.AddWithValue("@dat", Request.QueryString("iddate"))
cmd.ExecuteNonQuery()
Label1.ForeColor = Color.DarkGreen
Label1.Text = "Congratulations! You have been registered for this class. An email has been placed in your inbox with registration details. If email is not in your inbox within 10 minutes (usually, immediately), please look into your spam box."
Catch ex As Exception
'If the message failed at some point, let the user know
Label1.ForeColor = System.Drawing.Color.Red
Label1.Text = ex.Message
End Try
Conn.Close()
End Sub