How to check CheckListBox item with single click?

I think you are looking for

CheckOnClick property

set it to true

Gets or sets a value indicating whether the check box should be toggled when an item is selected.

I just finished working through an issue where I had set CheckOnClick to True via the designer, but the UI was still requiring a second click to check items. What I found is that for whatever reason, the designer file was not updating when I changed the value. To resolve, I went into the designer file and added a line

this.Product_Group_CheckedListBox.CheckOnClick = true;

After this, it worked as expected. Not sure why the designer didn't update, but maybe this workaround will help someone.

Set the property at Design Time in this way

or by code:

CheckedListBox.CheckOnClick = true;