open modal dialog from code behind fires but no page

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SharePoint2010

I have a SP2010 site and I am trying to open a modal dialog as a result of a button click.
I have searched and tried everything that I have seen and have had no luck. Here is the aspx page script and the code behind which fires but does not render the page.

function OpenAssignDialog(sID) {
        var dialogOptions = {
            url: "../jo_dreamsheet/add.aspx?sID=" + sID,
            autoSize: true,
            allowMaximize: false,
            dialogReturnValueCallback: onCloseCallback
        };
        var did = SP.UI.ModalDialog.showModalDialog(dialogOptions)
    }

    function onCloseCallback(dialogResult, returnValue) {
        window.top.location = "../jo_dreamsheet/dreamsheet.aspx";
    }

This is the code behind that everyone seems to say should work.

protected void btn_click(object sender, EventArgs e)
{
string bin = bin_label.Text;
           ClientScript.RegisterStartupScript(this.GetType(), "", "SP.UI.ModalDialog.showModalDialog({ url: '../jo_dreamsheet/add.aspx?sID=" + bin + "'}); return false;", true);

In desperate need of help. Please be specific as possible, seems most answers I can find seem to assume information that is not available.