Private Sub button2_Click(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles button2.Click
    If loginpasswordtx.Text.Length > 1 And loginpasswordtx.Text.Length > 1 And My.Settings.SQLConnectionString.Length > 5 Then
        Try
            Dim cnn As New SqlConnection(My.Settings.SQLConnectionString)
            Dim cmd = New SqlCommand("SELECT AppUser,AppUserPass FROM OrderAppUsers WHERE AppUser=@AppUser AND AppUserPass=@AppUserPass", cnn)
            cmd.Parameters.Add(New SqlParameter("@AppUser", createuserAppUser.Text))
            cmd.Parameters.Add(New SqlParameter("@AppUserPass", MD5StringHash(loginpasswordtx.Text)))
            cnn.Open()

            Dim obj As Object = cmd.ExecuteScalar()
            If obj = Nothing Then
                MsgBox("Faild to Log in, check your log in info")
                cnn.Close()
                Return
            End If
            cnn.Close()
        Catch ex As SqlException
            MsgBox(ex.Message)
            Return
        End Try

        MsgBox("Logged in Successfully")
    End If
End Sub

Try
            Dim cnnstring As String = String.Format("Server={0};Database={1};Trusted_Connection=True;", createuserServerTx.Text, createuserDatabaseTx.Text)
            Dim cnn As New SqlConnection(cnnstring)
            Dim cmd As New SqlCommand("INSERT INTO OrderAppUsers VALUES (@AppUser, @AppUserPass)", cnn)
            cmd.Parameters.Add(New SqlParameter("@AppUser", createuserAppUser.Text))
            cmd.Parameters.Add(New SqlParameter("@AppUserPass", MD5StringHash(createuserpassword.Text)))
            cnn.Open()
            cmd.ExecuteNonQuery()
            cnn.Close()
            MsgBox("User Crated Successfully")
            LayoutControl1.Visibility = Windows.Visibility.Collapsed
            My.Settings.SQLConnectionString = cnnstring
            My.Settings.Save()
        Catch ex As SqlException
            MsgBox(ex.Message)
        End Try

Private Function MD5StringHash(ByVal strString As String) As String
    Dim MD5 As New MD5CryptoServiceProvider
    Dim Data As Byte()
    Dim Result As Byte()
    Dim R As String = ""
    Dim Temp As String = ""

    Data = Encoding.ASCII.GetBytes(strString)
    Result = MD5.ComputeHash(Data)
    For i As Integer = 0 To Result.Length - 1
        Temp = Hex(3 * Result(i) + 1)
        If Len(Temp) = 1 Then Temp = "0" & Temp
        R += Temp
    Next
    Return R
End Function

cmd.Parameters.AddWithValue("@AppUser", createuserAppUser.Text)
cmd.Parameters.AddWithValue("@AppUserPass", MD5StringHash(loginpasswordtx.Text))

cmd.Parameters.Add("@AppUser", SqlDbType.VarChar)
cmd.Parameters("@AppUser").Value = createuserAppUser.Text
cmd.Parameters.Add("@AppUserPass", SqlDbType.VarChar)
cmd.Parameters("@AppUserPass").Value = MD5StringHash(loginpasswordtx.Text)

SELECT COUNT(*)
FROM OrderAppUsers
WHERE AppUser=@AppUser AND AppUserPass=@AppUserPass

Dim obj As int = Cint(cmd.ExecuteScalar())

If obj = 0 Then
    MsgBox("Faild to Log in, check your log in info")
    '' other codes
End If

Using cnn As New SqlConnection(My.Settings.SQLConnectionString)
    Using cmd = New SqlCommand("SELECT COUNT(*) FROM OrderAppUsers WHERE AppUser=@AppUser AND AppUserPass=@AppUserPass", cnn)
        cmd.Parameters.AddWithValue("@AppUser", createuserAppUser.Text)
        cmd.Parameters.AddWithValue("@AppUserPass", MD5StringHash(loginpasswordtx.Text))
        cmd.CommandType = CommandType.Text
        Try
            cnn.Open()
            Dim obj As int = Cint(cmd.ExecuteScalar())
            If obj = 0 Then
                MsgBox("Faild to Log in, check your log in info")
            Else
                 MsgBox("Logged in Successfully")
            End If
        Catch(ex As SqlException)
             MsgBox(ex.Message.ToString())
        End Try
    End Using
End Using