How to determine if a value of a key exist in my settings vb.net - vb.net

Question

i have start to develop a new application to generate md5 hashes from strings and the it save automatic to my.settings.md5_hashes
and now i need to check if a certain value all ready exist in my settings md5_hashes. i have find some examples but it give me all ways a error on it
the error
Error 1 Value of type 'System.Collections.Specialized.StringCollection' cannot be converted to 'String'.
how can i check if a value its all ready exist on my settings?
This is my code
Public Class Form3
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
If My.Settings.md5_hashes = (TextBox1.Text) Then
End If
If Not My.Settings.md5_hashes = (TextBox1.Text) Then
Me.Show()
End If
End Sub
End Class
This is the code to generate the hashes and save it to my.settings.md5_hashes
Imports System.Text
Imports System.Security.Cryptography
Imports System
Imports System.Collections
Imports System.Collections.Specialized
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
My.Settings.md5_hashes.Clear()
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim md5 As MD5 = System.Security.Cryptography.MD5.Create()
Dim inputBytes As Byte() = System.Text.Encoding.ASCII.GetBytes(TextBox1.Text)
Dim hash As Byte() = md5.ComputeHash(inputBytes)
Dim sb As New StringBuilder()
For i As Integer = 0 To hash.Length - 1
sb.Append(hash(i).ToString("x2"))
Next
TextBox2.Text = sb.ToString
ListBox1.Items.Add(TextBox1.Text + "<--->" + TextBox2.Text)
My.Settings.md5_hashes.Add(TextBox1.Text + "<--->" + TextBox2.Text)
My.Settings.Save()
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
For Each item In My.Settings.md5_hashes
ListBox1.Items.Add(item)
Next
Timer1.Start()
End Sub
Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
End Sub
Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
TextBox1.Text = ""
TextBox2.Text = ""
ListBox1.Items.Clear()
End Sub
Private Sub Button4_Click(sender As Object, e As EventArgs) Handles Button4.Click
Form2.Show()
End Sub
Private Sub Button5_Click(sender As Object, e As EventArgs) Handles Button5.Click
Dim W As IO.StreamWriter
Dim i As Integer
W = New IO.StreamWriter("C:\MD5.txt", True)
For i = 0 To ListBox1.Items.Count - 1
W.WriteLine(ListBox1.Items.Item(i))
Next
W.Close()
MsgBox("You File Is Save You Can Locate It At C:\MD5.txt")
End Sub
Private Sub Button6_Click(sender As Object, e As EventArgs) Handles Button6.Click
Form3.Show()
End Sub
End Class
well i have just change some part of the code
this is my new code
Imports System.Text
Imports System.Security.Cryptography
Imports System
Imports System.Collections
Imports System.Collections.Specialized
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'My.Settings.md5_hashes.Clear()
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim md5 As MD5 = System.Security.Cryptography.MD5.Create()
Dim inputBytes As Byte() = System.Text.Encoding.ASCII.GetBytes(TextBox1.Text)
Dim hash As Byte() = md5.ComputeHash(inputBytes)
Dim sb As New StringBuilder()
For i As Integer = 0 To hash.Length - 1
sb.Append(hash(i).ToString("x2"))
Next
TextBox2.Text = sb.ToString
ListBox1.Items.Add(TextBox1.Text)
ListBox1.Items.Add(TextBox2.Text)
My.Settings.md5_hashes.Add(TextBox1.Text)
My.Settings.md5_hashes.Add(TextBox2.Text)
My.Settings.md5_hashes.Add("<--->")
My.Settings.Save()
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
For Each item In My.Settings.md5_hashes
ListBox1.Items.Add(item)
Next
Timer1.Start()
End Sub
Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
End Sub
Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
TextBox1.Text = ""
TextBox2.Text = ""
ListBox1.Items.Clear()
End Sub
Private Sub Button4_Click(sender As Object, e As EventArgs) Handles Button4.Click
Form2.Show()
End Sub
Private Sub Button5_Click(sender As Object, e As EventArgs) Handles Button5.Click
Dim W As IO.StreamWriter
Dim i As Integer
W = New IO.StreamWriter("C:\MD5.txt", True)
For i = 0 To ListBox1.Items.Count - 1
W.WriteLine(ListBox1.Items.Item(i))
Next
W.Close()
MsgBox("You File Is Save You Can Locate It At C:\MD5.txt")
End Sub
Private Sub Button6_Click(sender As Object, e As EventArgs) Handles Button6.Click
Form3.Show()
End Sub
End Class
well now its return true but how can i get the value to show on a msgbox the results?
well i solved my self the way to get results of the name for example if i search with the name to retrieved the hash , but how to do if i search for a hash and get the name how to take the name i stored initial there ?

Answer 1

Use the Contains method:
If My.Settings.md5_hashes.Contains(TextBox1.Text) = True Then
'Hash exists, do something.
Else
'Hash does not exist, do something else.
End If
Tip: Check what members IntelliSense shows you when you type My.Settings.md5_hashes. (notice the dot on the end). By doing so you would most likely have found the answer to this yourself.
EDIT:
In your specific case it gets a little more complicated because you must separate the input and the hash before you can check that the hash exists.
Try this (this is for the first code you posted in the question):
Private Function HashExists(ByVal Hash As String) As Boolean
For Each Entry As String In My.Settings.md5_hashes 'Iterate through every hash entry.
Dim Parts As String() = Entry.Split(New String() {"<--->"}, 2, StringSplitOptions.RemoveEmptyEntries) 'Split the entry on "<--->".
If Parts.Length = 1 AndAlso Parts(0) = Hash Then
Return True 'No "<--->" was present, but the entire entry matches 'Hash'.
ElseIf Parts.Length >= 2 AndAlso Parts(1) = Hash
Return True 'The entry was split successfully and the second part and 'Hash' are equal.
End If
Next
Return False 'No valid hash found.
End Function
Then use this like:
If HashExists(TextBox1.Text) = True Then
'Hash exists, do something.
Else
'Hash does not exist, do something else.
End If
EDIT 2:
To get the name from a hash or a hash from a name the above code just need to be modified slightly to return any of the two parts.
Private Function GetEntry(ByVal Input As String, ByVal NameFromHash As Boolean) As String
For Each Entry As String In My.Settings.md5_hashes 'Iterate through every hash entry.
'Parts(0) is the name.
'Parts(1) is the hash.
Dim Parts As String() = Entry.Split(New String() {"<--->"}, 2, StringSplitOptions.RemoveEmptyEntries) 'Split the entry on "<--->".
If Parts.Length >= 2 Then
If NameFromHash = True AndAlso Parts(1) = Input Then
Return Parts(0) 'Input was a valid hash, return name.
ElseIf NameFromHash = False AndAlso Parts(0) = Input Then
Return Parts(1) 'Input was a valid name, return hash.
End If
End If
Next
Return Nothing 'No valid entry found.
End Function
Usage:
'Get the name from a hash.
Dim Name As String = GetEntry(TextBox1.Text, True)
'Get the hash from a name.
Dim Hash As String = GetEntry(TextBox1.Text, False)
If the function returns Nothing that means it couldn't find the name/hash you specified. To avoid getting a NullReferenceException you can check so in an If-statement:
'Name from hash.
If Name IsNot Nothing Then
'The specified hash was found, do something with the name.
Else
'Hash not found.
MessageBox.Show("The specified hash was not found.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
End If
'Hash from name.
If Hash IsNot Nothing Then
'The specified name was found, do something with the hash.
Else
'Name not found.
MessageBox.Show("The specified name was not found.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
End If