CODEWITHSUNDEEP
c#vb.netrandom
Alper
Alper

Reputation: 1

Help with random string function VB.NET?

I've made a function in C# to create a random string, but I wanted to convert it to VB.NET, unfortunately my knowledge of Visual Basic is much less than my knowledge of C#.

Here is my VB.NET function:

' Function will take in the number of characters in the string, as well as the optional parameter of chars to use in the random string
    Private Function RandomString(ByVal Chars_In_String As Integer, Optional ByVal Valid_Chars As String = "qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM")
        ' Create a string to hold the resulting random string
        Dim ReturnMe As String = ""

        ' Loop variable
        Dim i As Integer = 0

        ' Run while loop while i is less than the desired number of Chars_In_String
        While i < Chars_In_String
            ' Each time through, add to ReturnMe (selecting a random character out of the string of all valid characters)
            ReturnMe += Valid_Chars(random.[Next](0, Valid_Chars.Length))
        End While

        ' Return the value of ReturnMe
        Return ReturnMe
    End Function
    ' Create a new instance of the Random class, using a time-dependant default seed value
    Dim random As New Random()

As you will see, its not much different from my C# version, except that since VB can take an optional parameter, I allow the user to select what characters to use in the string, or just use the default ones.

Here's the C# version of my function:

    private static string RandomString(int Chars_In_String)
    {
        // Create a string to contain all valid characters (in this case, just letters)
        string all = "qwertyuiopasdfghjklzxcvbnmQWERTYIOPASDFGHJKLZXCVBNM";

        // Create a variable that will be returned, it will hold the random string
        string ReturnMe = "";

        // Run for loop until we have reached the desired number of Chars_In_String
        for (int i = 0; i < Chars_In_String; i++)
        {
            // Each time through, add to ReturnMe (selecting a random character out of the string of all valid characters)
            ReturnMe += all[random.Next(0, all.Length)];
        } 

        // Return the value of ReturnMe
        return ReturnMe;
    }
    // Create a new instance of the Random class, using a time-dependant default seed value
    static Random random = new Random();

Again, there's not much different, but the part I'm really struggling on is the conversion between what is the 12th line of VB code, and the 13th line of C# code.

I didn't really know how to convert it to VB.NET (as I said, my knowledge of it is very limited), so I used an online converter. The result of the online converter runs with no errors, however when I try to call the function, no string appears.

In short, this C# code works fine: ReturnMe += all[random.Next(0, all.Length)];

However, this VB.NET code doesn't work: ReturnMe += Valid_Chars(random.[Next](0, Valid_Chars.Length))

How could I fix my VB.NET code?

Upvotes: 0

Views: 631

Answers (2)

Hans Passant
Hans Passant

Reputation: 941257

It doesn't have anything to do with the string indexing operation, it is correct. You are simply forgetting to increment the loop counter. Use the For keyword:

    Dim ReturnMe As String = ""
    For i As Integer = 1 To Chars_In_String
        ReturnMe += Valid_Chars(random.Next(0, Valid_Chars.Length))
    Next
    Return ReturnMe

A StringBuilder would be wise if Chars_In_String ever gets largish. Use the Shared keyword unless this code lives inside a Module.

Upvotes: 1

carlosfigueira
carlosfigueira

Reputation: 87218

There are a few issues in your function:

  • You're missing the increment of the while loop variable (this way the function fails with an OutOfMemoryException)
  • You shouldn't concatenate strings (even in the C# case). Use a StringBuilder instead.

This code should work

Private Shared Function RandomString(ByVal Chars_In_String As Integer, Optional ByVal Valid_Chars As String = "qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM") As String
    Dim sb As StringBuilder = new StringBuilder()

    Dim i As Integer = 0
    Dim random As New Random()

    While i < Chars_In_String
        sb.Append(Valid_Chars(random.[Next](0, Valid_Chars.Length)))
        i = i + 1
    End While

    Return sb.ToString()
End Function

Upvotes: 3

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