检查 TextBox 是否为空

Question

I'm currently programming a little login system and I'm trying to prevent users from creating an account with nothing typed into the TextBoxes. This is my current code for registering an account:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    TextBox1.Text = My.Settings.username
    TextBox2.Text = My.Settings.password

    If Trim(TextBox1.Text).Length < 1 AndAlso Trim(TextBox2.Text).Length < 1 Then
        MsgBox("Wrong username or password!")
    ElseIf Trim(TextBox1.Text).Length > 1 AndAlso Trim(TextBox2.Text).Length > 1 Then
        MsgBox("Your account was created!", MsgBoxStyle.Information, "Create")
        Me.Hide()
        Form1.Show()
    End If
End Sub

Somehow, it will always say "Wrong username or password" even if I type something in. How do I make it only respond "Wrong username or password" if the input is nothing?

Edit: I fixed the code. But how do i make it possible that the person can only login with the information he registered?

Answer 1

Please check if My.Settings.username and My.Settings.password have non empty values. You are replacing both text boxes' Text properties with those values. You could do something like:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    If Not String.IsNullOrWhitespace(My.Settings.username) Then
        TextBox1.Text = My.Settings.username
    End If
    If Not String.IsNullOrWhitespace(My.Settings.password) Then
        TextBox2.Text = My.Settings.password
    End If      


    If String.IsNullOrWhitespace(TextBox1.Text) or String.IsNullOrWhitespace(TextBox2.Text) Then
        MsgBox("Wrong username or password!")
...

Please note that in your code, you are not evaluating when TextBox1.Text.Trim().Length = 1 and/or TextBox2.Text.Trim().Length = 1

Answer 2

Can you try this? And as what Emilio mentioned above, please make sure that your My.Settings.username and My.Settings.password are not passing any values.

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
   TextBox1.Text = My.Settings.username
   TextBox2.Text = My.Settings.password

   If String.IsNullOrEmpty(TextBox1.Text) AndAlso String.IsNullOrEmpty(TextBox2.Text) Then
      MsgBox("Wrong username or password!")
   Else
      MsgBox("Your account was created!", MsgBoxStyle.Information, "Create")
      Me.Hide()
      Form1.Show()
   End If
End Sub