Creating data model dynamically with code

-Data Model- object is an essential part of EasyQuery framework. However, sometimes you need to add some entities, entity attributes or operators to the existing model or to fill it from scratch using DB metadata information got from another source. In these cases, you can use EasyQuery API to build the model dynamically. Finally, we add entities and entity attributes. Here is an example of creatin a small data model: two tables (Customers and Orders) with one link between them, 2 entities (Customer and Order correpondingly) and a few attributes in each entity.

Data Model

In short (and by its name), data model - is a model (representation) of some data stored in your database. It solves two major problems: Presents the data to the end user in a more friendly and familiar way. Contains some meta information that helps EasyQuery components to build query statements in SQL or other query languages. Any data model contains the following main sections:

Building data model dynamically by DB meta-information

It's easier to fill your model right in the code directly from your database, using meta-information

Building data model dynamically by information from a DataTable

Example of how to build data model by certain information from DataTable

Data Model Editor

About Data Model Editor

Here you can find detailed information about this instrument and guideline, how to use it to perform all needed tasks.

Building data model dynamically using code (version 3.x)

Here you can find all steps you need to perform

Dynamic PHP query builder with EasyQuery

Dynamic PHP query builder with EasyQuery

Create a query with sub-query by code

Example with code

Dynamically populate lists by information from other conditions — WebForms

A code snippet which demonstrates how to execute this task

Aggregate data

From this article you will see how to aggregate (count, sum, etc.) data in your queries.

Working with several data models

All EasyQuery demos works with one data model (and one database which corresponds to that model). Here we are going to describe how to add a selector that switches between two data models on your view/page and then how to setup a custom "model loader" to handle GetModel requests propertly. To make it possible to switch between these two models we need some selector element on our page. The only problem here - is to switch the database connection accordingly the the switches between the models. Now when the user selects an item in our model selector element on the client-side - our server-side code automatically loads the selected model and connects to a proper database (when necessary)..

Dynamically populate value lists by information from other conditions

Suppose we have a database with Customer entity which has Country and City attributes. For both these attributes we define the value editors which return the lists of available values (countries and cities correspondingly). Now let's imagine the user adds a condition with the Country attribute e.g. Hera the steps needed to implement such a functionality: Define a value editor for the City attribute as SQL LIST with Cities.@{{Customer.Country}} list name (here Customer.Country is the ID of the Country attribute in the Customer entity). Let's name it "CitesSqlValueList") and then in a value list resolver modify its SQL according the currently selected country and get the list of values using GetValueListAsync method of EasyQueryManager class: What's happening here.

Create virtual (calculated) attribute in you model

Virtual attributes: what are they for and how to add one

Building dynamic queries with EasyQuery and Entity Framework

Here we describe how EasyQuery helps to implement a query building UI for creating custom, dynamic queries in .NET projects which use Entity Framework (6.x)

Adding columns and conditions with code

Example of code for adding columns and conditions

Possible ways of data model creation and loading

EasyQuery components need a [data model](/$aid/03bc06b0-83ec-4040-97ef-a50ca004177f) (a user-friendly representation of your DB) for their work. There are several different ways to create the model and load it on your project's startup. This article will describe all of them in detail.

Navigate through data model entities and attributes

A code snippet which demonstrates how to run through data model entities and attributes

Dynamic populating of value lists in WinForms or WPF editions

Example of how to solve this problem

Adding a new operator to your data model

Here you can find all information about how to add a new operator to your data model either using Data Model Editor (DME) or with a code