CheckBox ocultar y mostrar contraseña

Public Class Form1

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        TextBox1.Text = "esto es una prueba de UseSystemPasswordChar"
        TextBox1.UseSystemPasswordChar = True
    End Sub

    Private Sub CheckBox1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged
        If CheckBox1.Checked Then
            TextBox1.UseSystemPasswordChar = False
        Else
            TextBox1.UseSystemPasswordChar = True
        End If
    End Sub
End Class

Crear un archivo log

Dim log As StreamWriter = Nothing
' log = Nothing
Try
log = New StreamWriter("log.txt", False, System.Text.Encoding.UTF8)
registro(log)
Catch ex As Exception
End Try

' Pasar a una función

Public Function registro(ByVal log As StreamWriter) As String
log.WriteLine("texto")
End Function

Array variable is used before assigned a value

Dim varreglo() As String = Array.CreateInstance(GetType(String), 0)

fuente: http://stackoverflow.com/questions/25853677/array-variable-is-used-before-assigned-a-value

Conectar con SQL

Imports System.Data.SqlClient

Dim conex As String = "Data Source=SQLEXPRESS;Network Library=DBMSSOCN;Initial Catalog=BD;User ID=invitado;password=p455w0rd;Persist Security Info=False;Max Pool Size=4000;Enlist=true;Pooling=true"
Dim con As New SqlConnection(conex)

        Try
            con.Open()
            ' Insertar código aquí.
        Catch ex As Exception
            MessageBox.Show("Error!")
        Finally
            con.Close()
        End Try

'Try
'Catch SqlEx As SqlException
'End Try

fuente1: https://msdn.microsoft.com/es-cl/library/cc437979(v=vs.71).aspx fuente2: https://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlexception(v=vs.110).aspx

Obtener directorio actual archivo ejecutable windows service

Dim path As String = System.IO.Path.GetDirectoryName(Application.ExecutablePath)
Path.GetDirectoryName(System.Reflection.Assembly.GetEntryAssembly().Location

Eliminar archivos de un directorio

Imports System.IO
Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim archivos() As String = Directory.GetFiles("c:\directorio", "*.*") ' sin backslash al final de la ruta del directorio
        For Each f As String In archivos
            File.Delete(f)
        Next
    End Sub
End Class

http://bit.ly/2f3pTKV

Retornar un arreglo (array)

Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim str As String = "hola,chao,hallo,bye"
        Dim datos() As String = split_data(str)
    End Sub
    Public Function split_data(ByVal str As String) As String()
        Return str.Split(",")
    End Function
End Class