DropDownList控件的基本用法

 

 

protected   void  Page_Load( object  sender, EventArgs e)
     ... {
        if (!IsPostBack)
        ...{
            DateTime dt = DateTime.Now;
            DropDownList2.Items.Add(dt.Year.ToString());
            DropDownList3.Items.Add(dt.Month.ToString());
            DropDownList4.Items.Add(dt.Day.ToString());
            DropDownList4.Items.Add("23");
        }
       
    }
// 加减乘除
     protected   void  Button1_Click( object  sender, EventArgs e)
     ... {
        int a = int.Parse(TextBox1.Text);
        int b = int.Parse(TextBox2.Text);
        int c = 0;

        switch(DropDownList1.SelectedValue)
        ...{
            case "+":
                c = a + b;
                Label2.Text = c.ToString();
                break;
            case "-":
                c = a - b;
                Label2.Text = c.ToString();
                break;
            case "*":
                c = a * b;
                Label2.Text = c.ToString();
                break;
            case "/":
                c = a / b;
                Label2.Text = c.ToString();
                break;
        }
    }
// DropDownList 改变index时发生的事件
     protected   void  DropDownList4_SelectedIndexChanged( object  sender, EventArgs e)
     ... {
        Response.Write(DropDownList2.SelectedValue+"-"+ DropDownList3.SelectedValue+"-"+DropDownList4.SelectedValue);
    }

 

// CheckBoxList 改变index时发生的事件
  protected   void  CheckBoxList1_SelectedIndexChanged( object  sender, EventArgs e)
     ... {
        for (int i = 0; i < CheckBoxList1.Items.Count; i++)
        ...{
            if (CheckBoxList1.Items[i].Selected)   //注意启用postback，这样可以实时观测
            ...{
                Response.Write(CheckBoxList1.Items[i].Text);
            }
        }
    }