将值传回asp.net中的服务器？

Question

In an asp.net application, I have the follow code in the aspx page:

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
   <% foreach (var questionPaper in QuestionPapers) { %>
    <div style="border-bottom: 1px solid; padding-bottom:20px">
        <%= questionPaper.University %><br/>
        <%= questionPaper.CourseName %>: <%= questionPaper.CourseCode %><br/>
        <%= questionPaper.Type %><br/>
        <%= questionPaper.Year %><br/>
        <asp:Button ID="View_Paper" runat="server" OnClick="ViewPaper" Text="View Paper"/>
    </div>
   <% } %>
</asp:Content>

I want to pass questionPaper.ID back to the ViewPaper() event handler on the server side, how do I do that?

    public void ViewPaper(object sender, EventArgs e)
    {

    }

Answer 1

My recommendation is to use a Repeater or a ListView control

• Use a Repeater if the data will be used as read-only

• Use a ListView if you want to page your results and/or allow the end user to perform CRUD operation over your data

For example, your code would look like this when using a Repeater and an ObjectDataSource controls:

ASPX

<asp:ObjectDataSource ID="ods" runat="server" 
    SelectMethod="GetQuestionPapers" 
    TypeName="Your_Namespace.PapersRepository">
</asp:ObjectDataSource>
<asp:Repeater runat="server" DataSourceID="ods" ID="r" OnItemCommand="r_ItemCommand">
    <ItemTemplate>
        <div style="border-bottom: 1px solid; padding-bottom:20px">
            <asp:HiddenField runat="server" ID="paperID" Value='<%# Eval("PaperID") %>'/>

            <asp:Label runat="server" ID="university" Text='<%# Eval("University") %>'/><br />
            <asp:Label runat="server" ID="courseName" Text='<%# Eval("CourseName") %>'/>:<asp:Label runat="server" ID="courseCode " Text='<%# Eval("CourseCode ") %>'/><br />
            <asp:Label runat="server" ID="paperType" Text='<%# Eval("Type") %>' /><br />
            <asp:Label runat="server" ID="year" Text='<%# Eval("Year") %>' /><br />
            <asp:Button ID="View_Paper" runat="server" Text="View Paper" CommandName="ViewPaperCommand"
            />
        </div>
    </ItemTemplate>
    <SeparatorTemplate>
        <hr />
    </SeparatorTemplate>
</asp:Repeater>

ASPX code behind

protected void r_ItemCommand(object sender, RepeaterCommandEventArgs e)
{
    switch (e.CommandName)
    {
        case "ViewPaperCommand":
            var hidden = e.Item.FindControl("paperID") as HiddenField;
            var myPaperID = hidden.Value;

            break;
    }
}

Papers repository class

namespace Your_Namespace 
{
    public class PapersRepository 
    {
        public IEnumerable < QuestionPaper > GetQuestionPapers() 
        {
            return QuestionPapers.AsEnumerable();
        }
    }
}

Answer 2

You could bind it to a control and then reference that control directly?

I know you have multiple questions papers being output, so that in itself is the issue. It's been a while since I have used webforms, but could you not use a repeater control which would give you a row context within which you could get the specific question paper id you are looking for?

Answer 3

Use a repeater. That kind of old skool ASP classic code has no place in ASP.Net projects. Here's an example: http://www.dotnetcurry.com/ShowArticle.aspx?ID=663

It is possible to customise a repeater to make a lightweight DataGrid or ListView equivalent too.