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Using Or operator in Select Case Statement in Visual Basic

maqskywalker
maqskywalker asked
on
I'm learning to use the Select Case statement in vb.

Select...Case Statement
https://docs.microsoft.com/en-us/dotnet/visual-basic/language-reference/statements/select-case-statement


I have a ASP.NET WebForms page using VB.

The example works fine.

vbsample.PNG
When I enter a name from one of the names in the button click event.
The message is displayed on the label.


This is my code.

Example1_SelectCase.aspx

<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Example1_SelectCase.aspx.vb" Inherits="Example1_SelectCase" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <table>
        <tr>
            <td><asp:Label ID="lblCaption" runat="server" Text="Enter FirstName:"></asp:Label></td>
            <td>
                <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            </td>
            <td>
                <asp:Button ID="Button1" runat="server" Text="Button" />
            </td>
        </tr>
        <tr>
            <td>
                &nbsp;</td>
            <td>
                <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label></td>
            <td></td>
        </tr>
    </table>
    </div>
    </form>
</body>
</html>

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Example1_SelectCase.aspx.vb

Partial Class Example1_SelectCase
    Inherits System.Web.UI.Page

    ' Select Case Statement
    'https://docs.microsoft.com/en-us/dotnet/visual-basic/language-reference/statements/select-case-statement

    Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

        Dim varFirstName As String

        ' get textbox value and store in variable
        varFirstName = TextBox1.Text

        Select Case varFirstName
            Case "Bob"
                Label1.Text = "Hi Bob"
            Case "Beth"
                Label1.Text = "Hi Beth"
            Case "John"
                Label1.Text = "Hi John"
            Case "Billy", "Willy"
                Label1.Text = "Hi Billy or Willy"
            Case "Joe"
                Label1.Text = "Hi Joe"
            Case "Susan"
                Label1.Text = "Hi Susan"
        End Select

    End Sub
End Class

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In one of the case statements I have this:

            Case "Billy", "Willy"
                Label1.Text = "Hi Billy or Willy"

In this article
https://docs.microsoft.com/en-us/dotnet/visual-basic/language-reference/statements/select-case-statement

It states the following:

A Case statement with multiple clauses can exhibit behavior known as short-circuiting. Visual Basic evaluates the clauses from left to right, and if one produces a match with testexpression, the remaining clauses are not evaluated. Short-circuiting can improve performance, but it can produce unexpected results if you are expecting every expression in expressionlist to be evaluated.

Is it better to use an Or operator?
How do I revise this case statement to use the Or operator instead?

            Case "Billy", "Willy"
                Label1.Text = "Hi Billy or Willy"

So if I type either Billy OR Willy then display "Hi Billy or Willy" on the label.
Comment
Watch Question

Senior .Net Consultant
Top Expert 2016
Commented:
in that very specific case, you don't need to replace the short-circuiting with a regular Or because you are comparing against constant value (Billy or Willy). You are not running an expression. I wrote an article 10 years ago that explains what is short-circuiting: https://www.emoreau.com/Entries/Articles/2008/04/Short-circuiting-mainly-in-VBNet-and-SQL-Server.aspx