MSCRM 4.0 n:n lookup field

We had customer, who wanted to have n:n lookup field in MSCRM 4.0.

This is unsupported solution, But Cool :)

That means he wanted to have a lookup in the field that acts like the "To" lookup in email activity but for all types of entities.

Walkthrough:
1) Create n:n relationship between the entities
For holding the actual n:n records.
2) Create n:1 relationship between the entities and place the lookup in the form.
It's just a dummy lookup we won't use it to really old data just do all the UI work for us.
3) Add JavaScript to the onload event:

var nnId = "new_account_contact"; // entity N:N relationship id

RetreiveAssociatedEntities = function(relationshipSchemaName, entity1SchemaName, entity1KeyValue, retreiveAttribute) {
    var fetchXml = "<fetch mapping='logical'>"
    + "  <entity name='" + relationshipSchemaName + "'>"
    + "    <all-attributes />"
    + "    <filter>"
    + "      <condition attribute='" + entity1SchemaName + "id' operator='eq' value ='" + entity1KeyValue + "' />"
    + "    </filter>"
    + "  </entity>"
    + "</fetch>";

    var fetchResults = Fetch(fetchXml);

    var nodeList = fetchResults.selectNodes("resultset/result");

    var returnList = new Array();
    if (nodeList == null || nodeList.length == 0) {
        return returnList;
    } else {
        for (i = 0; i < nodeList.length; i++) {
            var idValue = nodeList[i].selectSingleNode('./' + retreiveAttribute).nodeTypedValue;
            returnList[i] = idValue;
        }
        return returnList;
    }
}
MischiefMayhemSOAP = function(serviceUrl, xmlSoapBody, soapActionHeader, suppressError) {
    var xmlReq = "<?xml version='1.0' encoding='utf-8'?>"
    + "<soap:Envelope xmlns:soap='http://schemas.xmlsoap.org/soap/envelope/'"
    + "  xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'"
    + "  xmlns:xsd='http://www.w3.org/2001/XMLSchema'>"
    + GenerateAuthenticationHeader()
    + "  <soap:Body>"
    + xmlSoapBody
    + "  </soap:Body>"
    + "</soap:Envelope>";

    var httpObj = new ActiveXObject("Msxml2.XMLHTTP");

    httpObj.open("POST", serviceUrl, false);

    httpObj.setRequestHeader("SOAPAction", soapActionHeader);
    httpObj.setRequestHeader("Content-Type", "text/xml; charset=utf-8");
    httpObj.setRequestHeader("Content-Length", xmlReq.length);

    httpObj.send(xmlReq);

    var resultXml = httpObj.responseXML;

    var errorCount = resultXml.selectNodes("//error").length;
    if (errorCount != 0) {
        var msg = resultXml.selectSingleNode("//description").nodeTypedValue;

        if (typeof (suppressError) == "undefined" || suppressError == null) {
            alert("The following error was encountered: " + msg);
        }

        return null;
    } else {
        return resultXml;
    }
}

Fetch = function(fetchXml) {
    var xmlSoapBody = "<Fetch xmlns='http://schemas.microsoft.com/crm/2007/WebServices'>"
    + "  <fetchXml>"
    + FetchEncode(fetchXml)
    + "  </fetchXml>"
    + "</Fetch>";

    var fetchResponse = MischiefMayhemSOAP("/MSCRMServices/2007/CrmService.asmx", xmlSoapBody, "http://schemas.microsoft.com/crm/2007/WebServices/Fetch");

    if (fetchResponse != null) {
        var fetchResults = new ActiveXObject("Msxml2.DOMDocument");

        fetchResults.async = false;
        fetchResults.resolveExternals = false;
        fetchResults.loadXML(fetchResponse.text);

        return fetchResults;
    } else {
        return null;
    }
}
FetchEncode = function(strInput) //_HtmlEncode
{
    var c;
    var HtmlEncode = '';

    if (strInput == null) {
        return null;
    }
    if (strInput == '') {
        return '';
    }

    for (var cnt = 0; cnt < strInput.length; cnt++) {
        c = strInput.charCodeAt(cnt);

        if (((c > 96) && (c < 123)) ||
  ((c > 64) && (c < 91)) ||
  (c == 32) ||
  ((c > 47) && (c < 58)) ||
  (c == 46) ||
  (c == 44) ||
  (c == 45) ||
  (c == 95)) {
            HtmlEncode = HtmlEncode + String.fromCharCode(c);
        }
        else {
            HtmlEncode = HtmlEncode + '&#' + c + ';';
        }
    }

    return HtmlEncode;
}

FillMultiLookup = function() {
    debugger;
    var contacts = RetreiveAssociatedEntities(nnId, "account", crmForm.ObjectId, "contactid");
    var value = new Array();
    for (var i = 0; i < contacts.length; i++) {
        value[i] = new Object();
        value[i].id = contacts[i];
        value[i].name = RetreiveAssociatedEntities("contact", "contact", contacts[i], "fullname")[0];
        value[i].typename = "contact";
    }
    crmForm.all.new_contactn2nid.DataValue = value;
    return value;
}

AssociateEntities = function(moniker1name, moniker1id, moniker2name, moniker2id, RelationshipName) {
    var authenticationHeader = GenerateAuthenticationHeader();
    // Prepare the SOAP message.
    var xml = "<?xml version='1.0' encoding='utf-8'?>";
    xml += "<soap:Envelope xmlns:soap='http://schemas.xmlsoap.org/soap/envelope/' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance\' xmlns:xsd='http://www.w3.org/2001/XMLSchema\'>";
    xml += authenticationHeader;
    xml += "<soap:Body><Execute xmlns='http://schemas.microsoft.com/crm/2007/WebServices'><Request xsi:type='AssociateEntitiesRequest'>";
    xml += "<Moniker1><Id xmlns='http://schemas.microsoft.com/crm/2006/CoreTypes'>" + moniker1id + "</Id>";
    xml += "<Name xmlns='http://schemas.microsoft.com/crm/2006/CoreTypes'>" + moniker1name + "</Name></Moniker1>";
    xml += "<Moniker2><Id xmlns='http://schemas.microsoft.com/crm/2006/CoreTypes'>" + moniker2id + "</Id>";
    xml += "<Name xmlns='http://schemas.microsoft.com/crm/2006/CoreTypes'>" + moniker2name + "</Name></Moniker2>";
    xml += "<RelationshipName>" + RelationshipName + "</RelationshipName>";
    xml += "</Request></Execute></soap:Body></soap:Envelope>";

    // Prepare the xmlHttpObject and send the request.
    var xHReq = new ActiveXObject("Msxml2.XMLHTTP");
    xHReq.Open("POST", "/mscrmservices/2007/CrmService.asmx", false);
    xHReq.setRequestHeader("SOAPAction", "http://schemas.microsoft.com/crm/2007/WebServices/Execute");
    xHReq.setRequestHeader("Content-Type", "text/xml; charset=utf-8");
    xHReq.setRequestHeader("Content-Length", xml.length);
    xHReq.send(xml);

    // Capture the result.
    var resultXml = xHReq.responseXML;

    // Check for errors.
    var errorCount = resultXml.selectNodes('//error').length;

    if (errorCount != 0) {
        var msg = resultXml.selectSingleNode('//description').nodeTypedValue;
        alert(msg);
    }
}

DisassociateEntities = function(moniker1name, moniker1id, moniker2name, moniker2id, RelationshipName) {
    var authenticationHeader = GenerateAuthenticationHeader();
    // Prepare the SOAP message.
    var xml = "<?xml version='1.0' encoding='utf-8'?>";
    xml += "<soap:Envelope xmlns:soap='http://schemas.xmlsoap.org/soap/envelope/' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance\' xmlns:xsd='http://www.w3.org/2001/XMLSchema\'>";
    xml += authenticationHeader;
    xml += "<soap:Body><Execute xmlns='http://schemas.microsoft.com/crm/2007/WebServices'><Request xsi:type='DisassociateEntitiesRequest'>";
    xml += "<Moniker1><Id xmlns='http://schemas.microsoft.com/crm/2006/CoreTypes'>" + moniker1id + "</Id>";
    xml += "<Name xmlns='http://schemas.microsoft.com/crm/2006/CoreTypes'>" + moniker1name + "</Name></Moniker1>";
    xml += "<Moniker2><Id xmlns='http://schemas.microsoft.com/crm/2006/CoreTypes'>" + moniker2id + "</Id>";
    xml += "<Name xmlns='http://schemas.microsoft.com/crm/2006/CoreTypes'>" + moniker2name + "</Name></Moniker2>";
    xml += "<RelationshipName>" + RelationshipName + "</RelationshipName>";
    xml += "</Request></Execute></soap:Body></soap:Envelope>";

    // Prepare the xmlHttpObject and send the request.
    var xHReq = new ActiveXObject("Msxml2.XMLHTTP");
    xHReq.Open("POST", "/mscrmservices/2007/CrmService.asmx", false);
    xHReq.setRequestHeader("SOAPAction", "http://schemas.microsoft.com/crm/2007/WebServices/Execute");
    xHReq.setRequestHeader("Content-Type", "text/xml; charset=utf-8");
    xHReq.setRequestHeader("Content-Length", xml.length);
    xHReq.send(xml);

    // Capture the result.
    var resultXml = xHReq.responseXML;

    // Check for errors.
    var errorCount = resultXml.selectNodes('//error').length;

    if (errorCount != 0) {
        var msg = resultXml.selectSingleNode('//description').nodeTypedValue;
        alert(msg);
    }
}

//returns the item location in array if not found -1
GetIndexFromArray = function(item, recordArr) {
    for (var i = 0; i < recordArr.length; i++) {
        if (recordArr[i] != null && recordArr[i].id == item) {
            return i;
        }
    }
    return -1;
}

UpdateN2N = function() {
    debugger;
    var oldValues = RetreiveAssociatedEntities(nnId, "account", crmForm.ObjectId, "contactid");
    //if there's records in lookup
    if (crmForm.all.new_contactn2nid.DataValue != null) {
        //go over all the related records and remove them if not in the new list (lookup)
        var temp = crmForm.all.new_contactn2nid.DataValue;
        for (var i = 0; i < oldValues.length; i++) {
            //if not in the new list disassociate them
            var index = GetIndexFromArray(oldValues[i], temp);
            if (index == -1) {
                DisassociateEntities("account", crmForm.ObjectId, "contact", oldValues[i], nnId);
            }
            else { // if in the list remove them from the list
                temp[index] = null;
            }
        } //ends for
        //go over all the remaining records and associate them
        for (var i = 0; i < temp.length; i++) {
            if (temp[i] != null) {
                AssociateEntities("account", crmForm.ObjectId, "contact", temp[i].id, nnId);
            }
        }
    }
    else if (oldValues != null) {
        for (var i = 0; i < oldValues.length; i++) {
            DisassociateEntities("account", crmForm.ObjectId, "contact", oldValues[i], nnId);
        }
    }
}

document.getElementById("new_contactn2nid").setAttribute("lookupstyle", "multi");
FillMultiLookup();

4)Add JavaScript to the onchange event:

UpdateN2N();

5) Add JavaScript to the onsave event:

crmForm.all.new_contactn2nid.DefaultValue = crmForm.all.new_contactn2nid.DataValue;
crmForm.all.new_contactn2nid.DataValue = crmForm.all.new_contactn2nid.DefaultValue;
crmForm.all.new_contactn2nid.DataValue = null;

Description: First of all we made the lookup multi by changing lookstyle attribute.

document.getElementById("new_contactn2nid").setAttribute("lookupstyle","multi");

Next we filled the lookup with the n:n relationship values.

UpdateN2N();

After the user changes the values in the lookup we update the real n:n relationship The last obstacle was to prevent the form from updating the lookup with the multi records in it, otherwise it will throw an error and won't update. This is achieved by setting the default value of the lookup to current value, setting it back the default to the current and then removing everything from it.

crmForm.all.new_contactn2nid.DefaultValue = crmForm.all.new_contactn2nid.DataValue;
crmForm.all.new_contactn2nid.DataValue = crmForm.all.new_contactn2nid.DefaultValue;
crmForm.all.new_contactn2nid.DataValue = null;

Thanks to http://crmentropy.blogspot.com/2010/09/nn-relationship-utility-code-javascript.html For the AssociateEntities, DisassociateEntities, RetreiveAssociatedEntities  functions helping dealing with the Many-to-Many relationship.