Desactivar botón derecho mouse ComboBox

Private Sub cbmes_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles cbmes.MouseDown
        If e.Button = MouseButtons.Right Then
            cbmes.DroppedDown = True
        End If
    End Sub

Bloquear tecla Supr ComboBox

Private Sub cbmes_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles cbmes.KeyDown
        e.SuppressKeyPress = True
    End Sub

ComboBox no iniciar seleccionado

Seleccionar otro control...
TextBox.Select()

Recorrer combobox

For i As Integer = 0 To comboBox.Items.Count - 1
MessageBox.Show(comboBox.Items.Add(i))
Next

validar formato fecha

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim fecha As String = tbfecha.Text.Trim

Dim formats() As String = {"d-MM-yyyy", "dd-MM-yyyy",
      "dd-M-yyyy", "d-M-yyyy"} ' más de un formato

Dim format As String = "dd-MM-yyyy"
        Dim thisDT As DateTime = Nothing

        If DateTime.TryParseExact(fecha, format, Globalization.CultureInfo.InvariantCulture, Globalization.DateTimeStyles.None, thisDT) Then

            MessageBox.Show("ok!")

        Else

            MessageBox.Show("no!")
        End If
End Sub

fuente: https://stackoverflow.com/questions/24841806/validate-the-date-format-in-vb-net

cambiar font en TabControl

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        TabControl1.DrawMode = TabDrawMode.OwnerDrawFixed
    End Sub

Properties TabControl, SizeMode: Fixed
Properties ItemSize

 Dim fnt As Font = New Font(TabControl1.Font.FontFamily, 10, FontStyle.Bold)
'Dim BoldFont As New Font(TabControl1.Font, FontStyle.Bold)
 e.Graphics.DrawString(TabControl1.TabPages(e.Index).Text, fnt, Brushes.Black, e.Bounds)

Fuente:
http://www.vbforums.com/showthread.php?355093-Setting-selected-tabpage-header-text-to-bold
http://www.vbforums.com/showthread.php?355093-Setting-selected-tabpage-header-text-to-bold
http://www.vbforums.com/showthread.php?683624-RESOLVED-Setting-the-font-to-the-title-of-a-tab-page
https://stackoverflow.com/questions/38942995/increase-width-and-height-of-headers-in-tabcontrol

Private Sub TabControl1_DrawItem(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DrawItemEventArgs) Handles TabControl1.DrawItem
        Dim fnt As Font = New Font(TabControl1.Font.FontFamily, 11, FontStyle.Bold)
        e.Graphics.DrawString(TabControl1.TabPages(e.Index).Text, fnt, Brushes.Black, e.Bounds)
    End Sub

https://docs.microsoft.com/en-us/dotnet/framework/winforms/controls/how-to-display-side-aligned-tabs-with-tabcontrol

Restar días a una fecha

DECLARE @fechai VARCHAR(10) = '2017-08-01'
declare @f varchar(30) = dateadd (day,-8,convert (date,DATEADD(month, ((YEAR(CONVERT(DATE,@fechai)) - 1900) * 12) + MONTH(CONVERT(DATE,@fechai)), -1)))
print @f

Obtener el último día del mes sql

DECLARE @fechai VARCHAR(10) = '2018-04-01'
declare @f varchar(30) = convert (date,DATEADD(month, ((YEAR(CONVERT(DATE,@fechai)) - 1900) * 12) + MONTH(CONVERT(DATE,@fechai)), -1))
print @f

Sumar días a una fecha formato "yyyy-MM-dd" en sql

Ejemplo 1

declare @fechai varchar(10) = '2017-09-21'
declare @fechaok varchar(20)
set @fechaok = convert (date ,DATEADD(DAY,8,substring (@fechai,9,2) + substring (@fechai,5,3) +'-'+ substring (@fechai,1,4)))
print  @fechaok

Ejemplo 2

declare @fechai varchar(10) = '2017-09-21'
declare @fechaok varchar(20)
set @fechaok = convert (date ,DATEADD(DAY,8,CONVERT(date,@fechai)))
print  @fechaok

Sumar dígitos de una fecha, formato string

Dim fechafin As String = "2017-05-12"
Dim sum As Integer = fechafin.Split("-").Select(Function(n) Int32.Parse(n)).Sum()

query opcional

declare @q varchar(100)
SET @q = '33'
execute('select * from hist_DTE where tipo_DTE=' +@q+ '')

Deshabilitar selección azul Datagridview

dgvdte.DefaultCellStyle.SelectionBackColor = Color.White
dgvdte.DefaultCellStyle.SelectionForeColor = Color.Black

Guía de despacho con valores exentos

https://goo.gl/P9sHJ2 
indicador de traslado 1 y 5

cambiar tipos de datos en sql

SELECT CAST(YourVarcharCol AS INT) FROM Table , recomendado usar CAST
SELECT CONVERT(INT, YourVarcharCol) FROM Table , recomendado para fechas y otros