Argument not specified for parameter x of Private Function x(x As String) As String

[Modulus]

I'm getting this error in my VB.Net application:

Argument not specified for parameter 'strFileName' of 'Private Function GetMD5String(strFilename As String) As String

when trying to use a function called GetMD5String() in a Timer1_Tick sub.


I'm using this code:

Private Function GetMD5String(ByVal strFilename As String) As String

        Dim cMD5 = Security.Cryptography.MD5.Create
        Dim bytHash As Byte()
        Dim sb As New System.Text.StringBuilder
        Dim scanbox As New TextBox
        scanbox.Text = My.Computer.FileSystem.ReadAllText("viruslist.txt").ToString
        Me.OpenFileDialog1.FileName = strFilename

        Using cStream As New IO.FileStream(strFilename, IO.FileMode.Open, IO.FileAccess.Read, IO.FileShare.Read)

            bytHash = cMD5.ComputeHash(cStream)
        End Using

        For Each c In bytHash
            sb.Append(c.ToString("X2"))
        Next

        If scanbox.Text.Contains(sb.ToString) Then
            TextBox1.Text = (strFilename)
            Me.OpenFileDialog1.FileName = strFilename
            Detect.ShowDialog()
            WriteToLog("Malicious exploit detected.")
            Quarantinevb.ListBox1.Items.Add(strFilename)
        End If

        Return sb.ToString



    End Function

and this code for Timer1_Tick

 Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
        RefreshList()
        Timer1.Enabled = False 'Stops the timer
        Timer1.Enabled = True
        GetMD5String()
    End Sub

Why is GetMD5String() throwing me this error?

[si_the_geek]

Take a look at the function definition:

Private Function GetMD5String(ByVal strFilename As String) As String

The item(s) inside the brackets are values that you must pass to it when you call it, so in this case you must pass a String (which represents strFilename), so you might call it like this:

GetMD5String("C:\Folder\File.tmp")

However, GetMD5String is a function, which means it returns a value (in this case a String, as that it what is listed after the brackets in the function definition), so you probably want something like this:

Dim MD5 as String = GetMD5String("C:\Folder\File.tmp")
MessageBox.Show(MD5)

edit: Also note that there is lots of code inside the function that doesn't really belong in there, as everything to do with scanbox or OpenFileDialog1 is irrelevant to getting an MD5 string. All of that code should really be outside of that function, possibly in your Timer sub instead, or maybe in another sub (with an appropriate name) that you call from the Timer sub.

[si_the_geek]

This is how I recommend you split the function out:

Private Function GetMD5String(ByVal strFilename As String) As String

        Dim cMD5 = Security.Cryptography.MD5.Create
        Dim bytHash As Byte()
        Dim sb As New System.Text.StringBuilder

        Using cStream As New IO.FileStream(strFilename, IO.FileMode.Open, IO.FileAccess.Read, IO.FileShare.Read)
            bytHash = cMD5.ComputeHash(cStream)
        End Using

        For Each c In bytHash
            sb.Append(c.ToString("X2"))
        Next

        Return sb.ToString

    End Function

    Private Sub CheckFile(strFilename As String)
        Dim scanbox As New TextBox
        scanbox.Text = My.Computer.FileSystem.ReadAllText("viruslist.txt").ToString
        Me.OpenFileDialog1.FileName = strFilename

        Dim MD5 as String = GetMD5String(strFilename)

        If scanbox.Text.Contains(MD5) Then
            TextBox1.Text = strFilename
            Me.OpenFileDialog1.FileName = strFilename
            Detect.ShowDialog()
            WriteToLog("Malicious exploit detected.")
            Quarantinevb.ListBox1.Items.Add(strFilename)
        End If

    End Sub

Now GetMD5String just gets an MD5 string, and CheckFile does the rest of the steps (which I reckon is checking a file).

The usage of this code would now be a bit simpler, eg:

CheckFile("C:\Folder\File.tmp")

Note that there are several things in the code that I've moved to CheckFile that are odd, for example I don't understand what the usage of OpenFileDialog1 is about, and I don't understand why scanbox is a TextBox (shouldn't it just be a String? that would store text, but use less memory and be a bit quicker).

It is also arguably not the best idea to be re-loading a file (viruslist.txt) every time you check a file, as that slows things down a lot (but it is a good idea if you expect viruslist.txt to change roughly as frequently as you check a file). Either way, it is wise to specify a full path to the file (as in my examples) instead of just the filename.