how to set minimum limit of a textbox vb.net

问题

I need to set a minimum length for a password that can be used in a textbox and then set a label which will say if it meets the minimum number of characters required. I know how to set the limit of characters, what I can't do is the part where it will show in a label as soon as I leave the textbox. I was thinking I need to use an event, like maybe Leave or LostFocus, but it's not working. Please help :(

回答1:

Ok, There are plenty of ways to do what you want to achieve. I personally like to a separate subroutine; if you need to change one thing, you wont have to edit every single event that has the same code

From what I can understand, something like this should help get you on your way.
Basically, we just setup a subroutine that will check to see if textbox1.text's length is more than five and we trigger the subroutine by using events such as a button click of if the textbox is clicked off.

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click ''save button
    checkPassword(TextBox1.Text)
    End Sub

    Private Sub TextBox1_Leave(sender As Object, e As EventArgs) Handles TextBox1.Leave
    checkPassword(TextBox1.Text)
    End Sub

    Private Sub checkPassword(password As String)
    If Not password.Length > 5 Then
        Label1.Text = "The password must be more than 5 charcharacters"
        TextBox1.Clear()
    Else
        Label1.Text = "Password accepted"
    End If
    End Sub

来源：https://stackoverflow.com/questions/44497302/how-to-set-minimum-limit-of-a-textbox-vb-net