CODEWITHSUNDEEP
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LabRat
LabRat

Reputation: 2014

VB.NET string equals ".abc" or ".xyz" else

How do I check for two possible strings else... (see example code)

Imports System.IO
Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        ' Input path.
        Dim p As String = TextBox1.Text
        ' Get extension.
        Dim extension As String = Path.GetExtension(p)

        If extension = ".abc" Or ".xyz" Then
            'nothing
            Label1.Text = "file type suported"
        Else
            Label1.Text = "Unsuported file type"
        End If
    End Sub
End Class

Upvotes: 1

Views: 790

Answers (6)

Matt Wilko
Matt Wilko

Reputation: 27322

@Tim Schmelter has already answered this quite thoroughly but:-

A Simple alternative is a Select statement - this will make it easier to update your code if you decide to support some other file type in the future:

Dim extension As String = Path.GetExtension(p)
Select Case extension
Case ".abc", ".xyz"
    Label1.Text = "file type suported"
Case Else
    Label1.Text = "unsupported file type"
End Select

Upvotes: 1

Alireza Maddah
Alireza Maddah

Reputation: 5885

Store all the supported extensions in a HashSet<string> structure and use the Contains method to check whether a specified extension is supported or not.

Imports System.IO
Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim supportedExtensions As New System.Collections.Generic.HashSet(Of String)
        supportedExtensions.Add(".abc")
        supportedExtensions.Add(".xyz")

        ' Input path.
        Dim p As String = TextBox1.Text
        ' Get extension.
        Dim extension As String = Path.GetExtension(p)

        If (supportedExtensions.Contains(extension)) Then
            'nothing
            Label1.Text = "file type suported"
        Else
            Label1.Text = "Unsuported file type"
        End If
    End Sub
End Class

UPDATE: As the number of supported extensions is increased, the OR conditions needed for extension support checking would go up and this would affect the legibility and maintainability of your code. Consequently, this code snippet offers you more readability.

Upvotes: 0

tinstaafl
tinstaafl

Reputation: 6948

You could also put your supported extensions in a string

Dim ValidExtensions As String = ".abc.xyz"

Then

If ValidExtensions.Contains(extension) Then
        Label1.Text = "file type suported"
Else
    Label1.Text = "Unsuported file type"
End If

This way it won't matter how many extensions you support or what changes you make to the list you only change the main string for the code to work.

Plus down the road if you decide to let the user change the supported file types you can make the changes programatically.

Upvotes: 2

Tim Schmelter
Tim Schmelter

Reputation: 460158

Just add the condition:

If extension = ".abc" OrElse extension = ".xyz" Then
    'nothing
        Label1.Text = "file type suported"
Else
    Label1.Text = "Unsuported file type"
End If

I have used OrElse because this checks the second condition only if the first condition returned false. For the same reason you should normally use AndAlso instead of And.

Consider this example:

Dim extension As String = Nothing
If extension Is Nothing Or extension.ToLower() = ".abc"
' ...

This throws an exception because extension is nothing but the Or causes the second condition to be evaluated anyway. This is safe:

If extension Is Nothing OrElse extension.ToLower() = ".abc"

Or versus OrElse

Another aproach is to use a positive-list and Enumerable.Contains:

Dim allowedExtensions = { ".abc", ".xyz" }
If allowedExtensions.Contains(extension) Then
    ' ...

Upvotes: 4

Dave Sexton
Dave Sexton

Reputation: 11188

I think you want alter one line to this:

If extension = ".abc" Or extension = ".xyz" Then

Upvotes: 0

4b0
4b0

Reputation: 22323

Try:

If extension = ".abc" Or extension = ".xyz" Then

Upvotes: 0

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