启动DropdownList 的AutoPostBack属性,然后在DropdownList 的SelectedIndexChanged事件里控制 protected void ddlPartyBAccount_SelectedIndexChanged(object sender, EventArgs e) { if (this.ddlPartyBAccount.SelectedValue == "1") { this.textbox1.Enabled = false; } else { this.textbox1.Enabled = true; } }