How to Retrieve Input from Backend Code to HTML OnClick ASP.NET

Question

In my existing project, I am still understanding the codes from the previous developer. I am uncertain how Eval in HTML forms are used.

I have an onclick action on my html form which downloads a file depending on the username, item number, and document type.

It contains a hard coded value of DocType=10.

It should be:

Group 1 = 10
Group 2 = 20
Group 3 = 30

Code snippet:

UserControl.ascx

<a href="#" onclick="openDialog('/SitePages/FileDownload.aspx?DocType=10&ItemNo=<%#Eval("ItemNo")%>&CustomerID=<%#Eval("CustomerID")%>')">

UserControl.ascx.cs

TBL_USER_PROFILEProvider uprovider = new TBL_USER_PROFILEProvider();

int DOC_TYPE;
// Document Types
const int G1_DOC_TYPE = 10;
const int G2_DOC_TYPE = 20;
const int G3_DOC_TYPE = 30;


protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        string userName = SPContext.Current.Web.CurrentUser.Name;
        TBL_USER_PROFILE p = uprovider.GetUser(userName);
        if (p != null)
        {
            // get group permissions
            List<string> G1List = uprovider.GetAccessByModuleName(p.UserProfileID, "Group1");
            List<string> G2List = uprovider.GetAccessByModuleName(p.UserProfileID, "Group2");
            List<string> G3List = uprovider.GetAccessByModuleName(p.UserProfileID, "Group3");

            // check doc type and deny access if not any
            if (G1List.Count != 0)
            {
                DOC_TYPE = G1_DOC_TYPE;
            }
            else if (G2List.Count != 0)
            {
                DOC_TYPE = G2_DOC_TYPE;
            }
            else if (G3List.Count != 0)
            {
                DOC_TYPE = G3_DOC_TYPE;
            }
            else
            {
                Response.Redirect("/SitePages/AccessDeny.aspx");
            }
        }
    }
}

May I know how can I pull the value of DOC_TYPE from code behind to my CS form?

---

p.s. DOC_TYPE is DocumentType, int from TBL_DOCUMENT table.

---

UPDATE after @tetsuya-yamamoto 's answer:

UserControl.ascx

<a href="#" runat="server" onclick="openDialog('/SitePages/FileDownload.aspx?DocType=<%# DocType %>&ItemNo=<%#Eval("ItemNo")%>&CustomerID=<%#Eval("CustomerID")%>')">

UserControl.ascx.cs

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        // other logic here

        if (G1List.Count != 0)
        {
            DOC_TYPE = G1_DOC_TYPE;
        }
        else if (G2List.Count != 0)
        {
            DOC_TYPE = G2_DOC_TYPE;
        }
        else if (G3List.Count != 0)
        {
            DOC_TYPE = G3_DOC_TYPE;
        }
        else
        {
            Response.Redirect("/SitePages/AccessDeny.aspx");
        }

        Page.DataBind();
    }
}

I will test out tomorrow as I am unable to access my server till then.

Do correct me if I corrected wrongly. Thank you!

Answer 1

Since you have an int variable with default access modifier, you need to create a property which has public or protected access modifier which has same data type for visibility in page markup:

int DOC_TYPE;

public int DocType 
{ 
   get 
   { 
       return DOC_TYPE; 
   } 
}

Then you can provide DocType property using projection syntax <%= DocType %>:

<a href="#" onclick="openDialog('/SitePages/FileDownload.aspx?DocType=<%= DocType %>&ItemNo=<%#Eval("ItemNo")%>&CustomerID=<%#Eval("CustomerID")%>')">

If you want to use that property in server control markup (i.e. having runat="server" attribute), then you should use <%# DocType %> binding syntax instead of <%= DocType %> projection syntax and call Page.DataBind() on Page_Load method:

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        // other logic here

        if (G1List.Count != 0)
        {
            DOC_TYPE = G1_DOC_TYPE;
        }
        else if (G2List.Count != 0)
        {
            DOC_TYPE = G2_DOC_TYPE;
        }
        else if (G3List.Count != 0)
        {
            DOC_TYPE = G3_DOC_TYPE;
        }
        else
        {
            Response.Redirect("/SitePages/AccessDeny.aspx");
        }

        Page.DataBind();
    }
}