Multiple validation in vb.net textbox - vb.net

Question

The problem i am having is after checking if the field is blank i want program to stop at that, right now it is going ahead and checking the username password also even though the field is blank and printing wrong username password. i am really new at this so please excuse the lack of knowledge
Private Sub ButtonOk_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonOk.Click
Try
Dim con As New SqlConnection("Initial Catalog=stock;Data source=.;integrated security=true")
Dim ds1 As New DataSet
Dim da1 As New SqlDataAdapter("select * from login where Name='" & Trim(txtusername.Text) & "'and password='" & Trim(txtpassword.Text) & "'", con)
If txtpassword.Text.Length = 0 Then
MsgBox("Password or username feild left blank")
End If
If da1.Fill(ds1) Then
adminmain.Show()
Me.Close()
Else
MsgBox("Invalid Password or Username")
End If
Catch ex As Exception
MsgBox(ex.Message)
End Try
End Sub

Answer 1

Then Return from the function.
If txtpassword.Text.Length = 0 Then
MsgBox("Password or username feild left blank")
Return
End If
But outside of the Try/Catch although it would work(a finally-block would be executed before the return statement). Actually the validation of the TextBox does not need to be inside of the Try/Catch, so imho it's confusing to return from within a Try/Catch.

Answer 2

Put your validations at the top of the Sub, and call Exit Sub as soon as an error is found.
Private Sub ButtonOk_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonOk.Click
If txtpassword.Text.Length = 0 Then
MsgBox("Password or username feild left blank")
Exit Sub
End If
'Other validations here
'Code to save changes here
End Sub
Also, you should remove that Try..Catch clause. If an unexpected error occurs you'll want to know what is the line number and stack trace of the error.