LINQ queries

Get started with LINQ

The recommended way to create queries is to use LINQ. If you are unfamiliar with LINQ, have a look at https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/linq/get-started-with-linq.

To fully use LINQ querying, make sure to have the following usings:

RequestResponse

using System.Linq;
using Stylelabs.M.Base.Querying;
using Stylelabs.M.Base.Querying.Linq;

Template

The LINQ template is as follows:

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where [conditions]
  orderby [property] ascending | descending
  select e);

Multiple conditions in the where clause can be chained by using &&.

orderby can be used to order results based on certain (system) properties, either ascending or descending. Multiple orderby statements can be used for more complex ordering.

Supported entity filters

The following filters on entities are supported for LINQ querying.

System properties

Id (long)
Identifier (long)
Definition
- id (long)
- name (string)
Created by
- user id (long)
- user name (string)
Modified by
- user id (long)
- user name (string)
Created on (DateTime)
Modified on (DateTime)

For example, to filter on id:

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.Id == entityId
  select e);

System properties

Depending on the system property data type:

long: ==, !=
string: ==, !=
DateTime: ==, !=, >, <, >=, <=

For example, to filter entities modified after the specified date:

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.ModifiedOn  dateTime
  select e);

Entity members

Property value (also supports filtering on values in specific cultures)
Relations (can be filtered on parent id only)

For example, to filter on a property value:

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.Property("Title") == "Logo"
  select e);

Supported comparison operators

The following comparison operators are supported for LINQ querying.

Properties

Depending on the property data type:

string: ==, !=
int: ==, !=, >, <, >=, <=
long: ==, !=, >, <, >=, <=
decimal: ==, !=, >, <, >=, <=
bool: ==, !=
DateTime: ==, !=, <, >, >=, <=
DateTimeOffset: ==, !=, >, <, >=, <=

For example, to filter entities where the title is not "Logo":

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.Property("Title") != "Logo"
  select e);

Additional property filters

The following property filters on entities are also supported for LINQ querying.

The 'in' filter

The In filter allows specifying a collection or comma separated values that, it allows filtering on multiple values instead of a single one.

The In filter is supported on:

Entity id
Entity identifier
Property values
Relation values (parent ids only)

Let's find the entities where the title is set to "Logo" or "Poster":

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.Property("Title").In("Logo", "Poster")
  select e);

String filters

String properties support some additional filters:

Contains: the value must contain the specified substring.
StartsWith: the value must start with the specified substring.
EndsWith: the value must end with the specified substring.

These filters are not case sensitive.

The following query can be used to find all entities with a Title property that contains "logo".

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.Property("Title").Contains("logo")
  select e);

Supported orderings

Ordering is supported on:

Entity id
Entity identifier
Definition id
Definition name
Created by user id
Created by user name
Modified by user id
Modified by user name
Created on
Modified on
Property values

For example, to order assets on creation date, and then by title:

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.DefinitionName == "M.Asset"
  orderby e.CreatedOn ascending
  orderby e.Property("Title") ascending
  select e);

Select options

Currently only load option and configuration operations are support on the select clause.

Load options and configurations

Warning

Since version 3.1, these operations are obsolete. The loading configurations and the query object are separated and should be passed as separate parameters (where applicable).

The following select options are supported:

InCultures: loads entities in specified cultures
WithProperties: loads specified properties on the entities
WithRelations: loads specified relations on the entities
LoadConfiguration: loads entities with specified load configuration

Multiple of these select options can be chained. The last operation will always overwrite the previous one where applicable.

In this example, we start from the default query load configuration (loads default culture, all properties and no relations) and we add the AssetTypeToAsset relation. The WithRelations overwrites the relation load option on the load configuration set earlier.

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where [conditions]
  select e.LoadConfiguration(QueryLoadConfiguration.Default)
  .WithRelations(new RelationLoadOption("AssetTypeToAsset")));

Note

For more information, see load configurations.

Result operators

skip (skip the first x entities) and take (return x entities) are also supported when using LINQ:

RequestResponse

var query = Query.CreateQuery(entities => 
  (from e in entities
  where [YOUR CONDITIONS]
  select e)
  .Skip(5)
  .Take(5));

This orders the entities by id descending, skips the first, or the newest, five entities, and then returns the next five entities.

Examples

The following is a list of examples. Most of these examples are very simple and self explanatory. Examples tend to be more complex towards the end.

By id

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.Id == entityId
  select e);

By identifier

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.Identifier == entityIdentifier
  select e);

By definition id

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.DefinitionId == definitionId
  select e);

By definition name

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.DefinitionName == "M.Asset"
  select e);

By created by user id

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.CreatedById == demoUserId
  select e);

By created by user name

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.CreatedByUsername == "M.Demo.User"
  select e);

By modified by user id

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.ModifiedById == demoUserId
  select e);

By modified by user name

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.ModifiedByUsername == "M.Demo.User"
  select e);

By created on

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.CreatedOn == dateTime
  select e);

Also possible between two dates:

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.CreatedOn  minDateTime && e.CreatedOn  maxDateTime
  select e);

By modified on

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.ModifiedOn == dateTime
  select e);

Also possible between two dates:

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.ModifiedOn  minDateTime && e.ModifiedOn  maxDateTime
  select e);

By property value

Finds all entities with a property Title that is set to "Logo".

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.Property("Title") == "Logo"
  select e);

By property value in specific culture

Finds all entities with a property Description that is set to "Hello world!" in the English culture.

RequestResponse

CultureInfo enUs = CultureInfo.GetCultureInfo("en-US");
var query = Query.CreateQuery(entities => 
  from e in entities
  where e.Property("Description", enUs) == "Hello world!"
  select e);

By relation parent value

The parent property can be accessed on the entity object to query on a specified relation. Querying on relations requires the relation name and the parent id to be specified.

RequestResponse

var query = Query.CreateQuery(entities => 
  from e in entities
  where e.Parent("AssetTypeToAsset") == assetTypeId
  select e);

A more advanced query

The following query gets the last ten assets made by "M.Demo.User", where the title is "Logo".

RequestResponse

var query = Query.CreateQuery(entities => 
  (from e in entities
   where e.DefinitionName == "M.Asset"
   && e.Property("Title") == "Logo"
   && e.CreatedByUsername == "M.Demo.User"
   orderby e.CreatedOn descending
   select e)
  .Take(10));