How can I change the state of checkboxs from a gridview in c#?

I have a gridview on an aspx page (WebForm) that has item name and checkbox. In the code behind in c#, I get a list of items names and I want that the checkboxes next to the items I already have will be checked.

I know to find the checkbox using (CheckBox)row.FindControl("CheckBox1"), but the Checked method doesn't work on it. Is there a way to do this?