Scenario: Show menu item in SharePoint ECB based on a condition e.g when versioning is enabled in the List or Document Library.

Solution: This can be done by creating a delegate control. 

<?xml version="1.0" encoding="utf-8"?>

<Elements xmlns="http://schemas.microsoft.com/sharepoint/">

       <Control Id="AdditionalPageHead"

           Sequence="90"

           ControlSrc="~/_CONTROLTEMPLATES/NY.ExportVersionHistory/ECBDelegateControl.ascx" />

</Elements>

In the ascx control we need to define Custom_AddListMenuItems(m, ctx) and Custom_AddDocLibMenuItems(m, ctx)

<script type="text/javascript">

    function Custom_AddListMenuItems(m, ctx) {

        AddECBMenuItems(m, ctx); 

    }

    function Custom_AddDocLibMenuItems(m, ctx) {

        AddECBMenuItems(m, ctx);

    }

    function AddECBMenuItems(m, ctx) {

        var pageUrl = ctx.HttpRoot + "/_layouts/NY.ExportVersionHistory/ExportVersionHistory.aspx?ID=" + currentItemID + "&amp;List=" + ctx.listName;

        if (ctx.verEnabled) {

            CAMOpt(m, "Export Version History", "window.open('" + pageUrl + "');", "/_layouts/images/NY.ExportVersionHistory/Excel_Small.png");

            CAMSep(m);

        }

    }

</script>