Disable resizing of a Windows Forms form

1. First, select the form.
2. Then, go to the properties menu.

3. And change the property "FormBorderStyle" from sizable to Fixed3D or FixedSingle.

   

Take a look at the FormBorderStyle property

form1.FormBorderStyle = FormBorderStyle.FixedSingle;

You may also want to remove the minimize and maximize buttons:

form1.MaximizeBox = false;
form1.MinimizeBox = false;