Hi nedash,

I have checked your code. Refer the below code there is no error i am getting as per your code, but it is not possible to put datalist inside label control.

HTML

<asp:DataList ID="DLclass" runat="server">
    <ItemTemplate>
        <asp:LinkButton ID="Linkbtnclass" runat="server" CssClass="lbldasteM" CommandArgument='<%# Eval("Name") %>'
            OnClick="Linkbtnclass_Click"><%# Eval("Name") %></asp:LinkButton>
        <div id="MM31">
        </div>
    </ItemTemplate>
</asp:DataList>
<asp:Label ID="Lblcontinue" runat="server" />
<div id="OtherPro1">
    <asp:DataList ID="DLrandom" runat="server" RepeatDirection="Horizontal" CssClass="dLrandom">
        <ItemTemplate>
            <div id="random">
                <a href='<%#"مستند.aspx?Id="+Eval("Id")%>' target="_blank">
                    <asp:Image ID="Imgrandom" runat="server" ImageUrl='<%# string.Format("Image/{0}",Eval("image")) %>'
                        CssClass="imgran"></asp:Image></a>
            </div>
            <div id="imgM1">
                <a href='<%#"مستند.aspx?Id="+Eval("Id")%>' target="_blank">
                    <asp:Label ID="Label18" runat="server" Text='<%# Eval("SectionName") %>' CssClass="lblRname"></asp:Label></a>
            </div>
        </ItemTemplate>
    </asp:DataList>
</div>
<asp:DataList ID="DLMostanad" runat="server" RepeatDirection="Vertical" CssClass="dLmostanad"
    Visible="false">
    <ItemTemplate>
        <div id="MainDL">
            <div id="MainDL1">
                <div id="MainDL11">
                    <asp:Label ID="Label3" runat="server" CssClass="lblcodeM" Text='<%# Eval("Code") %>'></asp:Label>
                    <asp:Label ID="Label4" runat="server" CssClass="lblnameM" Text='<%# Eval("Name") %>'></asp:Label>
                </div>
    </ItemTemplate>
</asp:DataList>

Code

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = new DataTable();
        dt.Columns.AddRange(new DataColumn[5] { 
            new DataColumn("Id", typeof(int)),
            new DataColumn("Name", typeof(string)),
            new DataColumn("SectionName",typeof(string)),
            new DataColumn("Image",typeof(string)),
            new DataColumn("Code",typeof(string))});
        dt.Rows.Add(1, "John Hammond", "SectionName1", "Chrysanthemum.jpg", "Code1");
        dt.Rows.Add(2, "Mudassar Khan", "SectionName2", "Desert.jpg", "Code2");
        dt.Rows.Add(3, "Suzanne Mathews", "SectionName3", "Hydrangeas.jpg", "Code3");
        dt.Rows.Add(4, "Robert Schidner", "SectionName4", "Jellyfish.jpg", "Code4");
        DLclass.DataSource = dt;
        DLclass.DataBind();
        DLrandom.DataSource = dt;
        DLrandom.DataBind();
        DLMostanad.DataSource = dt;
        DLMostanad.DataBind();
    }
}

protected void Linkbtnclass_Click(object sender, EventArgs e)
{
    Lblcontinue.Visible = !(DLMostanad.Visible = true);
    ViewState["LinkButtonValue"] = (sender as LinkButton).CommandArgument;
}