DropDownList and pagination conflict in gridview in .NET C#

Question

User1036972001 posted

hi guys,

this is my gridview in .NET c# with pagination

    <asp:GridView ID="gvProducts" AutoGenerateColumns="False" EmptyDataText="ko" EnableViewState="true"
        runat="server" DataKeyNames="ID" CssClass="mGrid" HorizontalAlign="Center"
        OnRowDataBound="gvProducts_RowDataBound"
        AllowPaging="True" PageSize="10"
        OnPageIndexChanging="OnPageIndexChanging">
        <AlternatingRowStyle CssClass="altrows" />
        <Columns>
            <asp:BoundField DataField="Nr" HeaderText="Nr." ReadOnly="true" HtmlEncode="false"
                        ItemStyle-CssClass="ddl_Class_new" ItemStyle-HorizontalAlign="Center" />

            <asp:TemplateField HeaderText="Status" ItemStyle-HorizontalAlign="Center">
                <ItemTemplate>
                    <asp:DropDownList ID="ddlstatus" runat="server" CssClass="pure-u-23-24"
                        AutoPostBack="true" OnSelectedIndexChanged="ddlstatus_SelectedIndexChanged">
                    </asp:DropDownList>
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
        <PagerTemplate>
            <asp:ImageButton ID="ImageButton1" runat="server" ImageUrl="/aspnet/img/bot_back_1.gif"
                CommandArgument="First" CommandName="Page" />
            <asp:ImageButton ID="ImageButton2" runat="server" ImageUrl="/aspnet/img/bot_back.gif"
                CommandArgument="Prev" CommandName="Page" />
            Page
                <asp:DropDownList ID="ddlPages" runat="server" AutoPostBack="True" CssClass="ddl_Class"
                    OnSelectedIndexChanged="ddlPages_SelectedIndexChanged">
                </asp:DropDownList>
            of
                <asp:Label ID="lblPageCount" runat="server"></asp:Label>
            <asp:ImageButton ID="ImageButton3" runat="server" ImageUrl="/aspnet/img/bot_next.gif"
                CommandArgument="Next" CommandName="Page" />
            <asp:ImageButton ID="ImageButton4" runat="server" ImageUrl="/aspnet/img/bot_next_1.gif"
                CommandArgument="Last" CommandName="Page" />
        </PagerTemplate>
    </asp:GridView>

on this gridview i have added this dropdownlist ddlstatus

   <asp:TemplateField HeaderText="Status" ItemStyle-HorizontalAlign="Center">
        <ItemTemplate>
            <asp:DropDownList ID="ddlstatus" runat="server" CssClass="pure-u-23-24"
                AutoPostBack="true" OnSelectedIndexChanged="ddlstatus_SelectedIndexChanged">
            </asp:DropDownList>
        </ItemTemplate>
    </asp:TemplateField>

when the dropdownlist ddlstatus is changed i need open new webpage on the browser

protected void ddlstatus_SelectedIndexChanged(object sender, EventArgs e)
{
    DropDownList ebb = (DropDownList)sender;
    GridViewRow gvr = (GridViewRow)ebb.NamingContainer;
    string dvalue = gvr.Cells[1].Text;
    ClientScript.RegisterStartupScript(this.GetType(), "OpenWindow", "window.open('newpage.aspx?ID=" + dvalue.ToString() + "');", true);
}

but the new webpage on the browser is opened also if try change page on gridview

protected void ddlPages_SelectedIndexChanged(object sender, EventArgs e)
{
    GridViewRow gvrPager = gvProducts.BottomPagerRow;
    DropDownList ddlPages = (DropDownList)gvrPager.Cells[0].FindControl("ddlPages");
    gvProducts.PageIndex = ddlPages.SelectedIndex;
    BindData();
}

protected void Paginate(object sender, CommandEventArgs e)
{
    int intCurIndex = gvProducts.PageIndex;

    switch (e.CommandArgument.ToString().ToLower())
    {
        case "First":
            gvProducts.PageIndex = 0;
            break;
        case "Prev":
            gvProducts.PageIndex = intCurIndex - 1;
            break;
        case "Next":
            gvProducts.PageIndex = intCurIndex + 1;
            break;
        case "Last":
            gvProducts.PageIndex = gvProducts.PageCount - 1;
            break;
    }
    gvProducts.DataBind();
}

protected void gvProducts_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
    gvProducts.PageIndex = e.NewPageIndex;
    BindData();
}

protected void OnPageIndexChanging(object sender, GridViewPageEventArgs e)
{
    gvProducts.PageIndex = e.NewPageIndex;
    BindData();
}

this is the the RowDataBound event

protected void gvProducts_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.Pager)
    {
        DropDownList ddl = (DropDownList)(e.Row.FindControl("ddlpages"));
        Label lblPageCount = (Label)e.Row.FindControl("lblPageCount");

        if (lblPageCount != null)
            lblPageCount.Text = gvProducts.PageCount.ToString();

        for (int i = 1; i <= gvProducts.PageCount; i++)
        {
            ddl.Items.Add(i.ToString());
        }

        ddl.SelectedIndex = gvProducts.PageIndex;

        if (gvProducts.PageIndex == 0)
        {
            ((ImageButton)e.Row.FindControl("ImageButton1")).Visible = false;
            ((ImageButton)e.Row.FindControl("ImageButton2")).Visible = false;
        }

        if (gvProducts.PageIndex + 1 == gvProducts.PageCount)
        {
            ((ImageButton)e.Row.FindControl("ImageButton3")).Visible = false;
            ((ImageButton)e.Row.FindControl("ImageButton4")).Visible = false;
        }
    }
}

i don't understand why this happens?

how to do resolve this?

thanks in advance for any help

Answer 1

User-1330468790 posted

Hi Koopers,

 

I tested your codes and found that there is a missing method for binding the data for the grid view and drop down list.

I made them by myself and ran the codes. No such error occurs. I suspected that the problem was located in those methods.

  

Could you please provide those codes for reproduce the problem?

 

My codes for your reference:

Gridview aspx:

<asp:GridView ID="gvProducts" AutoGenerateColumns="False" EmptyDataText="ko" EnableViewState="true"
                runat="server" DataKeyNames="ID" CssClass="mGrid" HorizontalAlign="Center"
                OnRowDataBound="gvProducts_RowDataBound"
                AllowPaging="True" PageSize="10"
                OnPageIndexChanging="OnPageIndexChanging">
                <AlternatingRowStyle CssClass="altrows" />
                <Columns>
                    <asp:BoundField DataField="Nr" HeaderText="Nr." ReadOnly="true" HtmlEncode="false"
                        ItemStyle-CssClass="ddl_Class_new" ItemStyle-HorizontalAlign="Center" />

                    <asp:TemplateField HeaderText="Status" ItemStyle-HorizontalAlign="Center">
                        <ItemTemplate>
                            <asp:DropDownList ID="ddlstatus" runat="server" CssClass="pure-u-23-24"
                                AutoPostBack="true" OnSelectedIndexChanged="ddlstatus_SelectedIndexChanged">
                            </asp:DropDownList>
                        </ItemTemplate>
                    </asp:TemplateField>
                </Columns>
                <PagerTemplate>
                    <asp:ImageButton ID="ImageButton1" runat="server" AlternateText="First" ImageUrl="/aspnet/img/bot_back_1.gif"
                        CommandArgument="First" CommandName="Page" />
                    <asp:ImageButton ID="ImageButton2" runat="server" AlternateText="Prev" ImageUrl="/aspnet/img/bot_back.gif"
                        CommandArgument="Prev" CommandName="Page" />
                    Page
                <asp:DropDownList ID="ddlPages" runat="server" AutoPostBack="True" CssClass="ddl_Class"
                    OnSelectedIndexChanged="ddlPages_SelectedIndexChanged">
                </asp:DropDownList>
                    of
                <asp:Label ID="lblPageCount" runat="server"></asp:Label>
                    <asp:ImageButton ID="ImageButton3" runat="server" AlternateText="Next" ImageUrl="/aspnet/img/bot_next.gif"
                        CommandArgument="Next" CommandName="Page" />
                    <asp:ImageButton ID="ImageButton4" runat="server" AlternateText="Last" ImageUrl="/aspnet/img/bot_next_1.gif"
                        CommandArgument="Last" CommandName="Page" />
                </PagerTemplate>
            </asp:GridView>

Grid View Code behind:

 // Simulation of the data
        private static DataTable _gridviewDT;
        public static DataTable GridviewDT
        {
            get
            {
                if (_gridviewDT is null)
                {
                    _gridviewDT = new DataTable();

                    _gridviewDT.Columns.Add("ID", typeof(int));
                    _gridviewDT.Columns.Add("Nr", typeof(int));


                    for(int i = 1; i< 50; i++)
                    {
                        _gridviewDT.Rows.Add(i,i);
                    }
                    

                }

                return _gridviewDT;
            }
            set
            {
                _gridviewDT = value;
            }
        }
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                BindData();
            }
        }

        protected void BindData()
        {
            gvProducts.DataSource = GridviewDT;
            gvProducts.DataBind();
        }

        protected void ddlPages_SelectedIndexChanged(object sender, EventArgs e)
        {
            GridViewRow gvrPager = gvProducts.BottomPagerRow;
            DropDownList ddlPages = (DropDownList)gvrPager.Cells[0].FindControl("ddlPages");
            gvProducts.PageIndex = ddlPages.SelectedIndex;
            BindData();
        }

        protected void ddlstatus_SelectedIndexChanged(object sender, EventArgs e)
        {
            DropDownList ebb = (DropDownList)sender;
            GridViewRow gvr = (GridViewRow)ebb.NamingContainer;
            string dvalue = gvr.Cells[0].Text;
            ClientScript.RegisterStartupScript(this.GetType(), "OpenWindow", "window.open('newpage.aspx?ID=" + dvalue.ToString() + "');", true);
        }

        protected void OnPageIndexChanging(object sender, GridViewPageEventArgs e)
        {
            gvProducts.PageIndex = e.NewPageIndex;
            BindData();
        }

        protected void gvProducts_RowDataBound(object sender, GridViewRowEventArgs e)
        {
            if (e.Row.RowType == DataControlRowType.Pager)
            {
                DropDownList ddl = (DropDownList)(e.Row.FindControl("ddlpages"));
                Label lblPageCount = (Label)e.Row.FindControl("lblPageCount");

                if (lblPageCount != null)
                    lblPageCount.Text = gvProducts.PageCount.ToString();

                for (int i = 1; i <= gvProducts.PageCount; i++)
                {
                    ddl.Items.Add(i.ToString());
                }

                ddl.SelectedIndex = gvProducts.PageIndex;

                if (gvProducts.PageIndex == 0)
                {
                    ((ImageButton)e.Row.FindControl("ImageButton1")).Visible = false;
                    ((ImageButton)e.Row.FindControl("ImageButton2")).Visible = false;
                }

                if (gvProducts.PageIndex + 1 == gvProducts.PageCount)
                {
                    ((ImageButton)e.Row.FindControl("ImageButton3")).Visible = false;
                    ((ImageButton)e.Row.FindControl("ImageButton4")).Visible = false;
                }
            }

            if(e.Row.RowType == DataControlRowType.DataRow)
            {
                DropDownList ddlPages = (DropDownList)e.Row.FindControl("ddlstatus");
                for(int i = 0; i < 4; i++)
                {
                    ddlPages.Items.Add(i.ToString());
                }
                

            }
        }

New Page aspx:

<form id="form1" runat="server">
        <div>
            <h1>The ID is <asp:Label ID="DisplayID" runat="server"></asp:Label></h1>
        </div>
    </form>

New Page Code behind:

protected void Page_Load(object sender, EventArgs e)
        {
            if(Request.QueryString["ID"] != null)
            {
                DisplayID.Text = Request.QueryString["ID"];
            }
        }

Demo:

 

Best regards,

Sean

Answer 2

User1036972001 posted

Hi Sean, thank you so much for help

the problem could be how the ddlstatus dropdownlist is populated on RowDataBound ?

please, see below

    private void mtddlstatus(GridViewRowEventArgs e)
    {
        int key = Convert.ToInt32(gvProducts.DataKeys[e.Row.RowIndex].Value.ToString());
        DropDownList ddlstatus = (DropDownList)(e.Row.FindControl("ddlstatus"));

        sql = @String.Format(" SELECT ");
        sql += String.Format(" CASE WHEN status = 0 THEN 'Open' ");
        sql += String.Format(" ELSE 'Close' END AS status ");
        sql += String.Format(" FROM `tbl_status` ");
        sql += String.Format(" WHERE ID = @paramID; ");

        using (MySqlConnection myConnectionString =
          new MySqlConnection(ConfigurationManager.ConnectionStrings["cn"].ConnectionString))
        {
            using (MySqlCommand cmd =
                new MySqlCommand(sql, myConnectionString))
            {
                cmd.Parameters.AddWithValue("@paramID", key.ToString());

                MySqlDataAdapter adapter =
                    new MySqlDataAdapter(cmd);

                DataTable dt = new DataTable();
                adapter.Fill(dt);
                ddlstatus.DataSource = dt;

                ddlstatus.DataTextField = "status";
                ddlstatus.DataValueField = "status";
                ddlstatus.DataBind();
                string selectedStatus = DataBinder.Eval(e.Row.DataItem, "status").ToString();
                ddlstatus.Items.FindByValue(selectedStatus).Selected = true;
                ddlstatus.Items.Insert(0, new ListItem("=== === ===", "0"));
                ddlstatus.Items.Insert(0, new ListItem("Open/Forward", "0"));
            }
        }
    }

    protected void gvProducts_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            mtddlstatus(e);
        }
    }