Use the SplitContainer.Panel2MinSize property to prevent the splitter from moving too close to the right or bottom edge of the container. For example, you might want to prevent some of the display area of a System.Windows.Forms.TreeView from being covered.

If the SplitContainer.Orientation property is Vertical (the default), SplitContainer.Panel2MinSize returns the minimum distance in pixels that the splitter can be from the right edge of SplitContainer.Panel2. If the SplitContainer.Orientation property is Horizontal, SplitContainer.Panel2MinSize returns the minimum distance in pixels that the splitter can be from the bottom edge of SplitContainer.Panel2.