Optimistic Concurrency in Model-Driven Apps Forms.

OptimisticConcurrencyForm.js

//Optimistic Concurrency in Model-Driven Apps Forms
var MEA = window.MEA || {};
var OptimisticConcurrencyForm = MEA.OptimisticConcurrencyForm || {};

(function () {
    var versionNumber = null;
    var entityReference = null;
    this.OnLoad = async function (executionContext) {
        var eventArgs = executionContext.getEventArgs();
        if (eventArgs.getDataLoadState() == 1) {
            var formContext = executionContext.getFormContext();
            formContext.ui.addOnLoad(this.getVersionNumberOnLoad);
            formContext.data.entity.addOnSave(this.validateOnSave);
            formContext.data.entity.addOnPostSave(this.updateVersionNumberOnPostSave);
        }

    };
    this.getVersionNumberOnLoad = async function (loadCtx) {
        var formContext = loadCtx.getFormContext();
        if (formContext.ui.getFormType() == 2) {
            entityReference = formContext.data.entity.getEntityReference();
            var onLoadResult = await Xrm.WebApi.retrieveRecord(entityReference.entityType, entityReference.id, "?$select=versionnumber");
            versionNumber = onLoadResult["versionnumber"];
        }
    };
    this.validateOnSave = async function (saveCtx) {
        var validateRowVersion = (saveCtx, entityReference, versionNumber) => {
            return (async () => {
                var result = await Xrm.WebApi.retrieveRecord(entityReference.entityType, entityReference.id, "?$select=versionnumber");
                var versionNumberFromServer = result["versionnumber"];
                if (versionNumberFromServer == versionNumber) {
                    return true;
                }
                else {
                    saveCtx.getEventArgs().preventDefault();
                    return false;
                }
            })();
        };
        var formContext = saveCtx.getFormContext();
        if (formContext.ui.getFormType() == 2) {
            try {
                var validationResult = await validateRowVersion(saveCtx, entityReference, versionNumber);
                if (!validationResult) {
                    var errorOptions = { message: 'This record is already updated by another user! ' };
                    Xrm.Navigation.openErrorDialog(errorOptions);
                }
            }
            catch (error) {
                console.log(error);
            }
        }
    };
    this.updateVersionNumberOnPostSave = async function (postSaveCtx) {
        if (postSaveCtx.getEventArgs().getIsSaveSuccess()) {
            entityReference = postSaveCtx.getEventArgs().getEntityReference();
            result = await Xrm.WebApi.retrieveRecord(entityReference.entityType, entityReference.id, "?$select=versionnumber");
            versionNumber = result["versionnumber"];
        }
    }
}).call(OptimisticConcurrencyForm);