更改 GridView 分页索引时是否可以防止回发？

Question

I am trying to create my own online quiz website using ASP C#.

I tried to bind the question from database into gridview and set the page size of the gridview to 1. And then I tried to pull the answers option (4 option) into radioButton .

But when I tried to move from the 1 page of gridview to another page, the checked value lost. I know thats because of when we changed the gridview page, it will do a postback .

My Questions are:

1. Why I can't access my RadioButton from CodeBehind? Is it because of inside the Updatepanel ?
2. Is it possible if we want to do a page index change in gridview without postback ? Or,
3. is there another option to make my RadioButton checked value not lost when changing to the next page (next question) ?

here are my code :

** quiz.aspx : **

<asp:UpdatePanel ID="upd1" runat="server">
    <ContentTemplate>
        <asp:GridView ID="grdquestions" runat="server" EnableViewState="true" EnableSortingAndPagingCallbacks="false" OnPageIndexChanging="grdquestions_PageIndexChanging" AutoGenerateColumns="false" DataKeyNames="QuestionId" Width="100%" AllowPaging="True" AllowCustomPaging="False" PageSize="1" ViewStateMode="Enabled">
            <Columns>
                <asp:TemplateField HeaderText="DOJO eQuiz">
                    <ItemTemplate>
                        <table class="tableclass" id='<%#Eval("QuestionId") %>'>
                            <tr>
                                <td><b>Question : <%#Eval("Question") %></b>
                                    <asp:HiddenField ID="hdnquestionId" runat="server" />
                                </td>
                            </tr>
                            <tr>
                                <td>
                                    <table>

                                        <tr style="margin-top: 10px;">

                                            <td>
                                                <table class="tblOptions">
                                                    <tr>
                                                        <td>
                                                            <asp:RadioButton ID="rdOption1" AutoPostBack="true" runat="server" Text='<%#Eval("Option1") %>' GroupName="chcbox" />

                                                        </td>
                                                    </tr>
                                                    <tr>
                                                        <td>
                                                            <asp:RadioButton ID="rdOption2" runat="server" AutoPostBack="true" Text='<%#Eval("Option2") %>' GroupName="chcbox" />
                                                        </td>
                                                    </tr>
                                                    <tr>
                                                        <td>
                                                            <asp:RadioButton ID="rdOption3" runat="server" AutoPostBack="true" Text='<%#Eval("Option3") %>' GroupName="chcbox" />
                                                        </td>
                                                    </tr>
                                                    <tr>
                                                        <td>
                                                            <asp:RadioButton ID="rdOption4" runat="server" Text='<%#Eval("Option4") %>' GroupName="chcbox" />
                                                        </td>
                                                    </tr>
                                                    <tr>
                                                        <td>
                                                            <asp:Label ID="lbquestionstatus" runat="server"></asp:Label>
                                                        </td>
                                                    </tr>

                                                </table>
                                            </td>
                                        </tr>
                                    </table>
                                </td>
                            </tr>

                        </table>

                    </ItemTemplate>
                </asp:TemplateField>
            </Columns>
            <PagerStyle HorizontalAlign="Center" CssClass="GridPager" />
        </asp:GridView>
    </ContentTemplate>
</asp:UpdatePanel>

** quiz.aspx.cs **

protected void Page_Load(object sender, EventArgs e)
    {
        if (Session["username"] == null)
        {
            Response.Redirect("Login.aspx");

        }
        else
        {
            if (!Page.IsPostBack)
            {
                BindGrid();

            }
            else
            {
            }
        } 
    }


 public void BindGrid()
    {
        var sess = Session["username"].ToString();
        string a = sess.Substring(sess.Length - 1);

        SqlDataAdapter adp = new SqlDataAdapter("select * from dojoquiz order by " + a + "", ConfigurationManager.ConnectionStrings["dashboardConnectionString"].ToString());
        adp.Fill(dt);

        grdquestions.DataSource = dt;
        grdquestions.DataBind();
    }

protected void grdquestions_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            RadioButtonList rdlstOptions = (RadioButtonList)e.Row.FindControl("rdlstOptions");
            HiddenField hdnquestionId = (HiddenField)e.Row.FindControl("hdnquestionId");
            if (rdlstOptions != null && hdnquestionId != null)
            {
                DataRow[] result = dt.Select("questionid=" + (Convert.ToInt32(hdnquestionId.Value)));
                DataView view = new DataView();
                view.Table = dt;
                view.RowFilter = "questionid=" + (Convert.ToInt32(hdnquestionId.Value));
                if (view.Table.Rows.Count > 0)
                {
                    DataTable dt1 = new DataTable();
                    dt1 = view.ToTable();
                }
            }
        }
    }

    protected void grdquestions_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
        grdquestions.PageIndex = e.NewPageIndex;
        this.BindGrid();
    }

Thank you for any help and suggestions.

Answer 1

If the sql query is not change, then don't do DataBind() on post back, but you still need to give him the data source to get the data. So your code must be as:

protected void Page_Load(object sender, EventArgs e)
{
    BindGrid();
}

public void BindGrid()
{
    var sess = Session["username"].ToString();
    string a = sess.Substring(sess.Length - 1);

    SqlDataAdapter adp = new SqlDataAdapter("select * from dojoquiz order by " + a + "", ConfigurationManager.ConnectionStrings["dashboardConnectionString"].ToString());
    adp.Fill(dt);

    grdquestions.DataSource = dt;

    if (!Page.IsPostBack)
        grdquestions.DataBind();
}

Its not possible with out post back to change page or do thinks on GridView, but if you make it correct this is not an issue.