Visual Basic

if char.isdigit(e.keychar) = false then
    if e.keychar = cchar("-") or e.keychar = cchar(".") then
        e.handled  = false
    else
        e.handled = true
    end if
else
    e.handled = false
end if 

if char.isdigit(e.keychar) = false then 'check if it's a number if its not do below:  
    if e.keychar = cchar("-") then ' if its a minus
        if me.textbox1.selectionstart = 0 then 'check if the cursor is at the start
            if me.textbox1.text.contains("-") = false then 'check if there is one already
                e.handled = false 'allow it if its at the start and the only one
            else
                e.handled = true 'otherwise don't allow it
            end if
        else
            e.handled = true 'if its not at start don't allow it
        end if
    elseif e.keychar = cchar(".") then ' if its a decimal place
        if me.textbox1.text.contains(".") = false then 'check if there is one already
            e.handled = false 'allow it if there is not one already
        else
            e.handled = true 'if there is one already don't allow it
        end if
    else
        e.handled = true 'if its not a number, a minus or a decimal point, don't allow it
    end if 
end if 

Try
    Dim i As Decimal = CDec(TextBox1.Text)
    TextBox2.Text = i
    MsgBox("Ok!")
Catch ex As Exception
    MsgBox("Doh!")
End Try

SELECT IdColumn, SomeColumn, SomeOtherColumn FROM TableName

Dim conn As New SqlConnection(connectionString)
Dim comm As New SqlCommand("SELECT IdColumn, SomeColumn FROM SomeTable", conn)
Dim da As New SqlDataAdapter(comm)
Dim cb As New SqlCommandBuilder(da)

Dim ds As New DataSet()
da.Fill(ds)

Return ds