How do I prevent a form from being resized by the user?

To prevent users from resizing, set the FormBoderStyle to Fixed3D or FixedDialog from properties window or from code

frmYour.BorderStyle = System.WinForms.FormBorderStyle.Fixed3D

And set the WindowState property to Maximized, set the MaximizeBox and MinimizeBox properties to false.

To prevent the user from moving around, override WndProc

Protected Overrides Sub WndProc(ByRef m As Message)
        Const WM_NCLBUTTONDOWN As Integer = 161
        Const WM_SYSCOMMAND As Integer = 274
        Const HTCAPTION As Integer = 2
        Const SC_MOVE As Integer = 61456

        If (m.Msg = WM_SYSCOMMAND) And (m.WParam.ToInt32() = SC_MOVE) Then
            Return
        End If

        If (m.Msg = WM_NCLBUTTONDOWN) And (m.WParam.ToInt32() = HTCAPTION) Then
            Return
        End If

        MyBase.WndProc(m)
    End Sub

//Set fixed border
yourForm.FormBorderStyle = System.Windows.Forms.FormBorderStyle.Fixed3D

//Set the state of your form to maximized       
yourForm.WindowState = FormWindowState.Maximized

//Disable the minimize box and the maximize box
yourForm.MinimizeBox = False
yourForm.MaximizeBox = False

Set the window start style as maximized. Then, hide the minimize and maximize buttons.

You can remove the UI to control this with:

frmYour.MinimizeBox = False
frmYour.MaximizeBox = False

If you want to prevent resize by dragging sizegrips and by the maximize button and by maximize by doubleclick on the header text, than insert the following code in the load event of the form:

    Me.FormBorderStyle = Windows.Forms.FormBorderStyle.FixedSingle ' Prevent size grips
    Me.MaximumSize = Me.Size ' Prevent maximize (also by doubleclick of header text)

Of course all choices of a formborderstyle beginning with Fixed will do.

Set the min and max size of form to same numbers. Do not show min and max buttons.