Writing ASP.NET code within an ASP literal

Question

I am writing an application that will display database queries. There are different tables and I would like to be able to choose between them with radio buttons. This is currently working properly, but now I am trying to figure out how to format the data repeater based on which table will be displayed (there are different numbers of columns, in a different order, etc.) I got the header to format successfully since it is just basic HTML, but the item template requires using asp inline code, which I believe is causing the problem.

relevant code from code-behind:

protected string showDataTableItemTemplate()
{
    string itemTemplateText = string.Empty;

    if (tableSelection == "parts")
    {
        itemTemplateText += "<td><%# DataBinder.Eval(Container,\"DataItem.PartNumber\") %></td>";
        itemTemplateText += "<td><%# DataBinder.Eval(Container,\"DataItem.Description\") %></td>";

    }
    else if (tableSelection == "package")
    {
        itemTemplateText += "<td><%# DataBinder.Eval(Container,\"DataItem.PackageNumber\") %></td>";
        itemTemplateText += "<td><%# DataBinder.Eval(Container,\"DataItem.Description\") %></td>";

    }
    else if (tableSelection == "product")
    {
        itemTemplateText += "<td><%# DataBinder.Eval(Container,\"DataItem.ProductNumber\") %></td>";
        itemTemplateText += "<td><%# DataBinder.Eval(Container,\"DataItem.Description\") %></td>";
    }
    return itemTemplateText;
}

Then I just have the literal defined like this in the aspx:

<asp:Literal runat="server" Text='<%#showDataTableItemTemplate() %>'></asp:Literal>

Is there another way to do this?

EDIT: I now have the following:

    protected void DataRepeater_ItemDataBound(object sender, RepeaterItemEventArgs e)
    {
        LiteralControl itemTemplateLiteral = new LiteralControl();
        itemTemplateLiteral = (LiteralControl)FindControl("itemTemplate");
        string itemTemplateText = string.Empty;

        if (tableSelection == "parts")
        {
            itemTemplateText += "<td><%# DataBinder.Eval(Container,\"DataItem.PartNumber\") %></td>";
            itemTemplateText += "<td><%# DataBinder.Eval(Container,\"DataItem.Description\") %></td>";

        }
        else if (tableSelection == "package")
        {
            itemTemplateText += "<td><%# DataBinder.Eval(Container,\"DataItem.PackageNumber\") %></td>";
            itemTemplateText += "<td><%# DataBinder.Eval(Container,\"DataItem.Description\") %></td>";

        }
        else if (tableSelection == "product")
        {
            itemTemplateText += "<td><%# DataBinder.Eval(Container,\"DataItem.ProductNumber\") %></td>";
            itemTemplateText += "<td><%# DataBinder.Eval(Container,\"DataItem.Description\") %></td>";

        }
        itemTemplateLiteral.Text = itemTemplateText;
    }

The compiler keeps telling me that there is an Object reference not set to an instance of an object. error. Also, Am I correct in trying to set the Text property still? (Wasn't that what I was trying to avoid by using this method?)

Use switch(tableSelection) instead of nested if

abatishchev
– abatishchev

2012-06-06 17:49:56 +00:00
Commented Jun 6, 2012 at 17:49 — abatishchev
– abatishchev, Commented Jun 6, 2012 at 17:49

Oded · Accepted Answer · 2012-06-06 14:54:29Z

3

You should have an event handler for the OnItemDataBound event of the template control and in it use FindControl to locate the Literal control and assign values to it using the e.Item.DataItem.

What your current code is doing is simply assigning strings to the literal - these will not be evaluated as part of page markup because they are not part of the markup.

answered Jun 6, 2012 at 14:54

Oded

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5 Comments

Kyle Preiksa Over a year ago

What is the difference between 'OnDataBind' and 'OnItemDataBound'? Do I need to use the latter since this occurs for each piece of data?

Oded Over a year ago

@Kyle - Sorry, I did mean OnItemDataBound.

Kyle Preiksa Over a year ago

Ok, so I created the OnItemDataBound (and the OnDataBind as well just in case I need it.) I declared a Control type variable Control itemTemplateLiteral = FindControl("itemTemplateText"); Is this correct? when I try e. the only methods are Equals, GetHashCode, ToString, and GetType

Kyle Preiksa Over a year ago

Ok, i figured that last part out. I was using the standard EventArgs rather than the RepeaterItemEventArgs Now, how to assign values using the dataItem

Oded Over a year ago

@Kyle - You need to cast the Control returned by FindControl to the correct type (in this case LiteralControl): var itemTemplateLiteral = (LiteralControl)FindControl("itemTemplateText");

mellodev · Accepted Answer · 2012-06-06 17:56:36Z

2

Bind the OnItemDataBound event, find the controls in the page and assign their values directly. Like so:

    protected void datalist1_ItemDataBound(object sender, DataListItemEventArgs e)
    {
        if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
        {

            // fetch values from the data bound row
            int identityID = e.Item.DataItem["columnname"];

            // Find your page control and assign values
            HtmlAnchor aBlogSbj = (HtmlAnchor)e.Item.FindControl("aBlogSbj");
            if (aBlogSbj != null)
            {
                aBlogSbj.HRef=identityID;
            }

        }

    }

answered Jun 6, 2012 at 17:56

mellodev

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1 Comment

Kyle Preiksa Over a year ago

Ok, I'm really not familiar with this web controls stuff... I want to display multiple columns in each row, and the code that calls those columns (the DataItem.Eval(Container, "columnname") ) changes based upon some user input. I can't seem to put things together

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