using System.Web.UI.HtmlControls; HtmlInputCheckBox chkBox1 = (HtmlInputCheckBox)this.FindControl("chkBox1"); protected void btnClick_Click(object sender, EventArgs e) { chkBox1.Click(); }Package/Library: System.Web Example 2: In this example, we have multiple HTML input checkbox elements with class "chkBoxClass". We can use the Click method to check/uncheck all checkboxes of this class when a button is clicked. ```csharp using System.Web.UI.HtmlControls; foreach (Control ctrl in this.Controls) { if (ctrl.GetType() == typeof(HtmlInputCheckBox)) { HtmlInputCheckBox chkBox = (HtmlInputCheckBox)ctrl; if (chkBox.Attributes["class"] == "chkBoxClass") { chkBox.Click(); } } } Package/Library: System.Web