根據另一個下拉列表在下拉列表中顯示數據

Question

我有兩個下拉列表，其中我正在從數據庫中顯示數據。 當在DropDownList2中選擇學院名稱時，為此必須在DropDownList1中顯示該學院的相關分支，為此我使用了存儲過程，當我通過傳遞參數手動運行它時，它運行良好。

但是在執行代碼時我會顯示所有分支。我需要任何回發嗎？ 在這種情況下請幫助我。

下面是我的代碼：

string queryString = "select College_Name from Colleges";
            string constring = System.Configuration.ConfigurationManager.ConnectionStrings["ConnDBForum"].ConnectionString;
            SqlConnection connection = new SqlConnection(constring);
            SqlCommand command = new SqlCommand(queryString, connection);
            connection.Open();
            DataTable dt = new DataTable();
            SqlDataAdapter ad = new SqlDataAdapter(command);
            ad.Fill(dt);

            if (dt.Rows.Count > 0)
            {
                DropDownList2.Items.Insert(0, new ListItem(String.Empty, String.Empty));
                DropDownList2.DataSource = dt;
                DropDownList2.DataTextField = "College_Name";
                DropDownList2.DataValueField = "College_Name";
                DropDownList2.DataBind();
                DropDownList2.Items.Insert(0, new ListItem(String.Empty, String.Empty));
            }


            SqlCommand Cmd = new SqlCommand("Branch_display", connection);
            Cmd.CommandType = CommandType.StoredProcedure;
            Cmd.Parameters.Add(new SqlParameter("@College_Name", DropDownList2.SelectedValue));
            DataTable dt1 = new DataTable();
            SqlDataAdapter ad1 = new SqlDataAdapter(Cmd);
            ad1.Fill(dt1);

            if (dt1.Rows.Count > 0)
            {

                DropDownList1.DataSource = dt1;
                DropDownList1.DataTextField = "Name";
                DropDownList1.DataValueField = "Name";
                DropDownList1.DataBind();
                DropDownList1.Items.Insert(0, new ListItem(String.Empty, String.Empty));
            }
            connection.Close();
        }

Answer 1

是的，您需要回發一些類似的信息，這應該有所幫助

      protected void Page_Load(object sender, EventArgs e)
        {

                if(!IsPostBack)
                {
          string queryString = "select College_Name from Colleges";
    string   constring=System.Configuration.ConfigurationManager.ConnectionStrings["ConnDBForum"].ConnectionString;

                SqlConnection connection = new SqlConnection(constring);
                SqlCommand command = new SqlCommand(queryString, connection);
                connection.Open();
                DataTable dt = new DataTable();
                SqlDataAdapter ad = new SqlDataAdapter(command);
                ad.Fill(dt);

                if (dt.Rows.Count > 0)
                {
                    DropDownList2.Items.Insert(0, new ListItem(String.Empty, String.Empty));
                    DropDownList2.DataSource = dt;
                    DropDownList2.DataTextField = "College_Name";
                    DropDownList2.DataValueField = "College_Name";
                    DropDownList2.DataBind();
                    DropDownList2.Items.Insert(0, new ListItem(String.Empty, String.Empty));

                }
 connection.Close();
            }
        }

asp.net呈現

  <asp:dropdownlist ID=" DropDownList2" runat="server" AutoPostBack="True" OnSelectedIndexChanged=" DropDownList2_SelectedIndexChanged">

和行動

private void  DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
{ 

string   constring=System.Configuration.ConfigurationManager.ConnectionStrings["ConnDBForum"].ConnectionString;


     SqlCommand Cmd = new SqlCommand("Branch_display", connection);
            Cmd.CommandType = CommandType.StoredProcedure;
            Cmd.Parameters.Add(new SqlParameter("@College_Name", DropDownList2.SelectedValue));
            DataTable dt1 = new DataTable();
            SqlDataAdapter ad1 = new SqlDataAdapter(Cmd);
            ad1.Fill(dt1);

            if (dt1.Rows.Count > 0)
            {

                DropDownList1.DataSource = dt1;
                DropDownList1.DataTextField = "Name";
                DropDownList1.DataValueField = "Name";
                DropDownList1.DataBind();
                DropDownList1.Items.Insert(0, new ListItem(String.Empty, String.Empty));
            }
            connection.Close();
}