Insert into database in vb not working - vb.net

Question

I have the below snippet of code whenever I try registering the username exist part seems to be executed even for a username that doesn't exist in the database. Don't know where am wrong here any help will be appreciated.
'Connecting to SQL Database and executing Query------------------------------------------
Dim Strconn As String = "Data Source=.\SQLEXPRESS; Database=QuizDB; Integrated Security = true"
Dim Strcmd As String = "INSERT INTO reg_info(uname,pass,fname,lname,dob,course,college) VALUES ('" & user_name.Text & "','" & con_pass.Text & "', '" & first_name.Text & "', '" & last_name.Text & "', '" & dob.Text & "', '" & course.Text & "', '" & college.Text & "');"
Dim da As New SqlDataAdapter
Dim ds As New DataSet
Dim sqlcmd As SqlCommand
sqlconn = New SqlConnection(Strconn)
Try
sqlconn.Open()
Catch ex As Exception
MsgBox("Could not connect to DataBase. Application will close now!", vbCritical, "Database Error")
End
End Try
sqlcmd = New SqlCommand(Strcmd, sqlconn)
da.SelectCommand = sqlcmd
sqlcmd.Dispose()
sqlconn.Close()
'Exception Handling-----------------------
Dim exc As Exception = Nothing
Try
da.Fill(ds)
Catch ex As Exception
exc = ex
Finally
If Not (exc) Is Nothing Then
MsgBox("User Name Already Exist. Please select a different User Name!", vbExclamation, "Already Exist")
user_name.Focus()
Else
MsgBox("Registration Successful.", vbInformation, "Successful")
Me.Close()
Login.Show()
End If
End Try

Answer 1

Here is a refactor of your code with some helpful guidance. I think this will compile, but if it does not, then you can do a little homework to figure out what is missing.
Try
' the USING block guarantees that the object's Close() and Dispose() methods are fired automatically when you exit the block
Using sqlconn As New SqlConnection("Data Source=.\SQLEXPRESS; Database=QuizDB; Integrated Security = true")
Using sqlcmd As SqlCommand = sqlconn.CreateCommand
With sqlcmd
.CommandType = CommandType.Text
' parameterized query to protect against SQL injection
.CommandText = "INSERT INTO reg_info(uname,pass,fname,lname,dob,course,college) VALUES (#username, #password, #firstname, #lastname, #dob, #course, #college)"
With .Parameters
.Clear()
.AddWithValue("#username", user_name.Text)
.AddWithValue("#password", con_pass.Text)
.AddWithValue("#firstname", first_name.Text)
.AddWithValue("#lastname", last_name.Text)
.AddWithValue("#dob", dob.Text)
.AddWithValue("#course", course.Text)
.AddWithValue("#college", college.Text)
End With
.ExecuteScalar() ' Actually executes the SQL command
End With
End Using
End Using
MsgBox("Registration successful")
Catch ex As Exception
' Any error in the TRY block will automatically jump to herem and the "ex" object will be an Exception object with populated properties
MsgBox("User name already exists. Error from database is " & ex.Message)
End Try