Use the SplitContainer.Panel1 property to configure the left panel of a vertical System.Windows.Forms.SplitContainer or the top panel of a horizontal System.Windows.Forms.SplitContainer. For example, you can specify the minimum size of the panel by changing the value of the SplitContainer.Panel1MinSize property, set the SplitContainer.FixedPanel property to Panel1 so that the panel remains the same size when the container is resized, or you can get or set the panel's SplitContainer.BackgroundImage and SplitContainer.BackgroundImageLayout properties.

You cannot remove SplitContainer.Panel1 from the System.Windows.Forms.SplitContainer.

If SplitContainer.Panel1 or SplitContainer.Panel2 contains no control that can receive the focus, the focus remains on the splitter when it is clicked. To change the focus to SplitContainer.Panel1 or SplitContainer.Panel2, set the SplitterPanel.TabIndex property of SplitContainer.Panel2 to 0 and the SplitterPanel.TabIndex property of SplitContainer.Panel1 to 1.